Pass Labs X600.8 600 Watt Monoblock Power Amplifier Review Highlights

Pass Labs manufactures preamplifiers and power amplifiers. They all have massive build quality, especially the Xs-300 Pure Class A monoblocks that we reviewed recently (each monoblock weighs 300 pounds).

They have a huge number of models spread out in three different lines: the .5’s, Xs, and now, the .8’s.

The Xs 300 is a monoblock that has 300 watts biased into Pure Class A. It’s heavy, expensive, sounds fantastic, but it’s $85,000 for a pair. The matching preamplifier is $38,000. In any part of the civilized world, that is long green.

However, “Sounds Fantastic” is a phrase that’s catchy. It’s something all audiophiles want. But, $85,000 is a little scary. So, how to get as much of the Xs sound, but not have to forget about buying that Tesla?

Pass figures it out. Just build the same thing with somewhat less transistors and power supply capacitors. And that is what you have in the .8 series. Their low end model, the X150.8 (MSRP: $6,400) is a stereo version, with 150 watts per channel, Class AB. The top model is the XA200.8 (MSRP: $40,000/pair), which is a monoblock with 200 watts RMS biased into Pure Class A. About midway is the model I am reviewing here, the X600.8, which has 600 watts RMS into 8 ohms, with the first 50 watts in Class A.

I tested them with a Pass Labs XP-20 preamplifier and Carver Amazing Mark IV ribbon speakers. Interconnect cables were Mogami and speaker cables were Wireworld.

Well, Nelson Pass nailed it. The X600.8’s sounded very much like the Xs 300’s, but with less bass slam and a bit less “sheen” on the musical instruments in the high frequencies (I notice it mostly on cymbals because I am a drummer – for instruments like an oboe or trumpet, I’m sure the same difference was there, but I could not really tell). Now, this bass slam I am referring to is not just at 20 Hz, but up to about 100 Hz or so.

In any case, I arranged the two models side by side (I had to turn on the room air conditioner even though it was 50⁰ F outside because of all that Class A bias). So, I was able to do a true A-B comparison very easily. Nevertheless, the differences were not something that would be a deal breaker by any means. I am not sure I would have heard the differences if I had to run to different rooms to listen to each pair of power amps. However, I suspect th XA200.8’s are closer in sound to the Xs 300’s (also closer in price).

Pass Labs X600.8 Monoblock Power Amplifier Review Highlights Summary

• Sounds very similar to the top-of-the-line Xs series
• Less Expensive than the Xs series
• Solid build quality
• Entry level model is much more affordable than Xs series

Introduction to the Pass Labs X600.8 Monoblock Power Amplifier Review

Pass Labs has been in business since 1991. That is not really a very long time, and yet, in those two decades, Pass has become a household name that stands for the best that high end audio has to offer. They have designed and built many models over those years, and currently offer 25 power amplifier models and 4 preamplifier models. That’s a huge lineup !

The Xs 300 monoblocks were a recent addition, representing their version of the State-of-the-Art in power amplfiers, which we reviewed. In that same review, we also tested the matching Xs Preamplifier.

The Xs series performed (and sold) so well, Pass decided to build a line of power amplifiers that had most, but not all, of the Xs series sound characteristics, in a range of price levels that most audiophiles could afford.

The .8 series was born.

It consists of the XA200.8, XA160.8, XA100.8, XA60.8, XA30.8 (the XA signifies that the entire power output is Class A, with the number before the .8 indicating how much power), the X600.8, X350.8 (Stereo), X250.8 (Stereo), X260.8, and X150.8 (Stereo).

In the current review, we report on the X600.8, which is rated at 600 watts RMS into 8 ohms, with the first 50 watts in Class A. I requested them in the 240 volt version to prevent voltage sag at high output. I have had several instances of high power amplifiers which use 120 volts, and the voltage sag when testing them at high output interfered with getting an accurate output measurement. I have a Variac, but the voltage sag was occasionally so low, I could not raise the voltage to 120 volts even with the Variac. So, 240 volt versions it will be with all high power amplifiers I test in the future.

The Design of the Pass Labs X600.8 Monoblock Power Amplifier

The design of the X600.8, and indeed, all of the .8 series, is similar to the Xs 300. The differentiating factor of the .8’s and Xs from the .5’s is the presence of a high power current source that is separate from the output devices. This allows deeper and punchier bass.

Here is a table that shows the principal differences between the Xs 300 and the X600.8:

The front panel is identical to other Pass Labs amplifiers, with a large round power meter. The difference between this power meter and those of other manufacturers is that the Pass Labs power meter needles don’t move unless you are beginning to output power beyond the Class A portion (50 watts into 8 ohms). In the case of the X600.8, the needle is steady at about an inch to the left of straight up. With the Xs 300, the needle resting spot is straight up, because the entire output is biased into Class A.

The rear panel is the same as well, with two sets of massive speaker binding posts, XLR and RCA inputs, On/Off toggle, Ground connector, and Trigger. The AC socket is grounded. As I mentioned, I requested a pair wired for 240 volts. This prevented voltage drop when the power output was high. I suggest that you do the same if you purchase this amp or the Xs 300’s. It will mean pulling a 240 volt line into your A/V room, but it’s worth it.

The amplifiers get very warm during use, because even just 50 watts of Class A generates plenty of heat dissipation.

The Pass Labs X600.8 Monoblock Power Amplifier In Use

I tested the X600.8 monoblocks with an OPPO BDP-105 universal player, Pass Labs XP-20 preamplifier, and Carver Amazing Mark IV speakers. Cables were Mogami interconnects and Wireworld speaker cables.

Angela Hewett published a set of CDs that contain all of Bach’s keyboard music (Hyperion LC 7533; CDs 44421 through 44435), played on piano regardless of any pieces that were originally composed for harpsichord. It’s a terrific set, and frankly, much more enjoyable on a piano. The sound intensity varied from light touch to heavy full handed, and the X600.8’s did their job well.

What I was listening for was the short transients at the initial strike of the hammer on each note, and a natural tonality, both of which were very good. When played loud, and with the lowest notes on the piano (the lowest key is 28 Hz), the Xs 300 had more punch. The body of all the notes (all the keys) had a bit more sheen. At modest volume, the bass sounded the same, but the sheen difference was still there. However, as I mentioned previously, I don’t think I would have noticed the difference in the sheen if the amplifiers had not been in the same room so I wouldn’t have been able to switch back and forth so quickly.

Now, it is time to remind you that Pass Lab designs are engineered by listening rather than just putting the circuit together for the lowest distortion possible within the budget. The bench tests showed considerable amounts of harmonics, but these were put there on purpose, or rather, the staff kept changing parts in the circuit here and there until they got the sound they wanted, and the harmonics fell where they might. They do not indicate an amplifier under stress. They are harmonics that produce the sound the Pass Labs staff felt was the most musical. It’s an unusual approach, but one that works. They are continuously back ordered on their amplifiers.

Copland’s Fanfare for the Common Man (Telarc CD-80078) is a track I have used more often in my amplifier and speaker reviews over the years than any other piece of music. The opening crash of gong and huge bass drum is a shock for any hifi system. The X600.8’s carried the day, remaining musical and non-harsh. After all, 600 watts is a lot of power. But, even a 600 watt amplifier can be pushed to its limits when peak demand is there. The X600.8’s didn’t seem to have any limits at all. A massive power transformer and plenty of power supply capacitance were the reason.

Violin is a great instrument to use for listening tests because harshness is easy to hear. This 2 CD set (Bridge 9371A/B) has Corelli violin sonatas that include an organ and archlute (looks a bit like a guitar). So, it would be easy to bury the violin detail in a deep organ note if there is much intermodulation distortion. Well, I enjoyed the album very much, because of the music, and the lack of said harshness which can make violins unlistenable. Also, the archlute kept its signature sound (plucked) through the organ accompaniment.

The Manhattan Transfer has been been around a long time, starting out as a “Du-Wop” group that you might hear at a burger joint (Bobby Sox required). This CD from 1997 still retains that kind of sound, without synthesizers (present in a 2009 CD). The quartet really knows how to rock, and this album (Atlantic B000002JD8) in particular, has it all the way through. It was great to be able to crank it up and still hear four distinct voices. (which was the test).

The Pass Labs X600.8 Monoblock Power Amplifier on the Bench

All distortion measurements were within an 80 kHz bandwidth. I used the XLR balanced input on the amplifier for the test signals.

At 1 kHz, 5 volts and 8 ohms, distortion was 0.023%. There were two harmonics, and the second ordered harmonic was predominant. There is quite a bit of low-level noise which contributes significantly to the measured number (THD+N). I cannot measure only THD on the Audio Precision, but I would estimate that the distortion component is about 0.008%.

If we look at a portion of this spectrum (second graph below: 10 Hz – 1 kHz), we can see that the noise is made up of hum spurs (60 Hz and its multiples). I don’t know where it is coming from, but I see it in many amplifier spectra, including those published in other magazines. In this particular instance, I suspect that it is at least partly due to having the amplifiers draw their power from a 240 volt wall socket, while the Audio Precision uses 120 volts. In any case, the noise is at a very low level.

With 5 volts into 4 ohms, distortion rose to 0.082%, and a third harmonic appeared.

Distortion at 22 volts output was significantly higher than at 5 volts, which is normal. Now, many harmonics were present, but the second ordered harmonic was still the predominant one. Again, the noise component is a significant contribution to the measurement.

Using 19 kHz and 20 kHz test tones, there were a lot of side peaks, which increased in height and number (mostly height) as I changed the signal from 5 volts to 22 volts, and the load from 8 ohms to 4 ohms.

IMD was 0.083% at 5 volts and 8 ohms, 0.317% at 5 volts and 4 ohms, 0.241% at 22 volts and 8 ohms, and 0.577% at 22 volts and 4 ohms. I used 22 volts (60.5 watts) to take the measurement in the Class AB portion of the output. The 5 volt measurements were within the Pure Class A portion.

THD+N vs. Frequency is shown below. The 20 volt measurement came close to clipping at 35 kHz, and at 4 ohms, surpassed clipping (1% THD+N) but, again, a portion of the measurement is noise, not harmonic distortion.

Measured power output at 8 ohms was 700 watts RMS at 1% THD+N, which is higher than spec.

At 4 ohms, power output was 1,050 watts RMS at clipping, which was lower than spec.

Measured Frequency Response was 10 Hz – 50 kHz, – 1.5 dB.

Conclusions about the Pass Labs X600.8 Monoblock Power Amplifier

Pass Labs appears to have nailed their intent to create an affordable line of power amplifiers that perform close to their statement Xs series. One or more of these power amps should be on your must-audition list if you are planning to upgrade your current setup.

The post Pass Labs X600.8 600 Watt Monoblock Power Amplifier Review appeared first on HomeTheaterHifi.com.

Yamaha AVENTAGE MX-A5000 Eleven-Channel Amplifier Review Highlights

I had a chance to take a look at Yamaha’s top of the line multi-channel amplifier, the AVENTAGE MX-A5000. I enjoyed my time with the MX-A5000. The unit easily handled anything that I threw at it from a content perspective and provides a level of installation flexibility that I’ve never before seen in a multi-channel amplifier. Installation and set-up is far from straight forward, but if you are looking for a unit that can handle a complex home theater setup or like to power your speakers in interesting ways, I’d most certainly encourage a look at the MX-A5000.

Yamaha AVENTAGE MX-A5000 Eleven-Channel Amplifier Highlights Summary

• Solid built quality
• Clean, understated look
• 11-channels at 150WPC
• Capable of astonishing installation flexibility
• Competent and neutral sounding
• Confusing setup

Introduction to the Yamaha ATENTAGE MX-A5000 Eleven-Channel Amplifier Review

Yamaha makes a lot of stuff. I own a Yamaha Vino 125 scooter that you can spot me on regularly during the months of June, July and August. Mine is the grey one – surfboard carrier attached. But the company has its roots in music and for as long as I’ve been involved in this hobby; Yamaha has been a well respected manufacturer of audio gear. I had a chance to take a look at the company’s top of the line multi-channel amplifier, the AVENTAGE MX-A5000. The MX-A5000 is one of the more unique amplifiers I’ve had in my home. With 11-channels of 150WPC power, and a design that allows for a dazzling array of set-up options, the MX-A5000 is easily the most flexible amp I’ve ever had a chance to review. The sound of the unit is clean and unobtrusive and is a terrific option for those looking for the ultimate in installation flexibility.

Design and Setup of the Yamaha AVENTAGE MX-A5000 Eleven-Channel Amplifier

The MX-A5000 weighs in at 56 lbs. While it’s not the burliest amp I’ve reviewed, it is solid enough in stature that I’m certain the UPS man was cursing my name as he brought it to our front door. The MX-A5000 arrived as expected – well but not overly packaged. The unit itself has an understated look: black with a large power button in the center and a speaker selector switch on the lower left. When powered up the power button is encircled with a blue light that is pleasing and not distracting. The power indicator is dimmable should you find it a little too bright for your tastes.

As I turned to the back of the unit I was greeted with a mind numbing array of inputs and speaker terminals. I was honestly flummoxed. I saw 11 balanced and unbalanced inputs. That made sense from a top-level – but there is one channel 1…a channel 2 left and right? Above each channel was a toggle switch for Channel Selection. What’s that all about? And the speaker terminals (nice quality, gold plated) – I count 13 – where did the other two come from? I swallowed my pride and grabbed the box to root out the manual.

Unfortunately, but not unexpectedly, I found the manual provided only marginal assistance. I skipped the section entitled “Advanced Speaker Configuration” and made my way to the appendix where a somewhat complex figure appeared to map out how audio signals were distributed within the system. When I thought that I had a decent understanding of what was going on I made my first attempt at connecting my Marantz AV8801 to the MX-AV5000 and the MX-AV5000 to my B&W 805D and HTM4’s and Paradigm Studio 10 surrounds. I fired up my system…and nothing happened. Hmmm…

I finally did get sound out of my speakers, but it took a bit of messing around. If you haven’t picked up on it yet, the Yamaha A5000 logic isn’t straight forward, at least to my brain. I’m not going to walk through all of the settings here, but I will walk through what the various configuration options will allow you to do. In its most basic configuration you can bring in 11 channels of audio, and amplify those 11 channels to 11 speakers. So if you have a setup with heights, widths, etc – you’ll be all set (this amp would be terrific for a full blow Dolby Atmos set-up). Stereo in a second or third zone? No problem. Bi-amp or even Tri-amp your main speakers? Yup. Two pairs of front speakers (say for theater and music)? No problem. Multiple speakers for one channel? That to. Essentially, Yamama has built in flexibility that’ll allow the A5000 to accommodate a speaker configuration you might be able to think up.

The Yamaha AVENTAGE MX-A5000 Eleven-Channel Amplifier In Use

Once I got the speaker configuration hammered out, I was ready to dive in.

Phish released its first studio album in five years this past summer. True to form the album is engineered flawlessly, this time by Bob Ezrin (Lou Reed, Pink Floyd, Peter Gabriel), and provides excellent demo material for any system.

Fuego is a more melodic album than Phish has produced in the past. Songs like “Waiting All Night” and “Wingsuit” bring in a new easiness that reflects the bands maturity (30 years and counting). The best compliment that I can give the A5000 is that it disappeared behind the B&W 805D’s, adding little discernable color to the music and allowing me to hear the B&W’s unencumbered. The A5000 easily handled the changes from the dreamy sounds of “Waiting All Night”, to the jam/funk of “555”. Anastasio’s guitar remained well balanced throughout, and there was ample power to handle Fishman’s often frenetic drum lines.

The B&W805’s are fully capable of running on their own without a sub – and for all of this listening I chose to run them in that fashion. The A5000 had no trouble handling the lower register and Gordon’s powerful bassline on tracks like “Halfway To the Moon”.

Like many teens, I had a Led Zeppelin “phase” and I still love “getting the Led out” from time to time. I continue to be pleasantly surprised with the recent renaissance that Led Zep frontman Robert Plant has gone through in the last several years. While some rockers from the 70’s have made careers playing the same music for decades, Plant has found a way to reinvent himself in the most exciting of ways. I dug the bluegrass focused “Raising Sand” and have had “Lullaby and…The Ceaseless Roar” on constant rotation recently.

The first release from this album was Rainbow. As he’s aged, Plants voice has taken on an ethereal and delicate quality; its still the same voice we heard wailing in “Whole lotta love” – but its been mellowed with age. That delicateness was easily conveyed by the A5000, and the subtleties of the track remained fully intact. Through the entire album, the A5000 remained neutral and uncoloring.

On multi-channel material the A5000 also performed quite well. I made use of several titles in my evaluation, including the 3D Blu-ray for Avatar – which has an impeccable DTS-HD soundtrack.

I had no issues at all with how the AV5000 handled Avatar. Powering my 5-channel setup, there was ample power available for a punchy and dynamic presentation. A terrific example of this is when Jake attempts to ride Mountain Banshee for the first time. This scene is a workout for any amplifier, and the AV5000 handled the huge swings in stride.

Whether in daily use on regular watching, or with more detailed and deep Blu-ray presentations, the AV5000 acted exactly as I want an amp to act: capable and unobtrusive.

Conclusions about the Yamaha AVENTAGE MX-A5000 Eleven-Channel Amplifier

The AV5000 was the first piece of electronics from Yamaha that I have ever had the pleasure of using. Yamaha has constructed a competent and highly flexible amp that is capable of adapting to event the most complex of set-ups. As may be evident from the set-up section of this review, the units design is not straightforward and the accompanying documentation fell short in helping to streamline installation. However, once set-up, the AV5000 proved quite adept at handling whatever I was able to throw at it. If you have a speaker setup that requires a unique powering configuration, or have lots of channels you need to power, the Yamaha AV5000 most certainly requires a look.

The post Yamaha AVENTAGE MX-A5000 Eleven-Channel Power Amplifier Review appeared first on HomeTheaterHifi.com.

Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier Review Highlights

Integrated amplifiers have never enjoyed the same respect audiophiles pay to separate components. Similarly, Class D amplification has been the “Scarlet Letter” of the high-end audio realm due to a sea of mass-market amplifiers that make more “noise” than “music”. Borrowing heavily from technologies developed for the cost-no-object Steinway Lyngdorf audio systems (yes, THAT Steinway) the TDAI-2170 aims not to simply level the high-end audio playing field, but to flip it on its head entirely. Fundamentally different from traditional Class D amplifiers, the sleek TDAI-2170 produces a sound so clean, so neutral, so devoid of any sonic signature, it disappears completely and restores the emotional response that made me fall in love with music to begin with.

Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier Highlights Summary

• Fully-digital, unbroken signal path maintains audio integrity which, according to Lyngdorf Audio, has no negative feedback loop
• “RoomPerfect” room correction software is incredibly easy to use and produces an immediately noticeable improvement in sound
• “Intersample Clipping Correction” combats the “Loudness War” and restores the lost fidelity at the cost of slightly decreased volume overall
• Modular design allows for adaptation to any listening environment
• Simple, intuitive interface makes navigation easy and customization a snap
• Completely disappears in any system, letting the music speak for itself
• “Blackground” – the most silent background of any audio component, of any type, at any cost

Introduction to the Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier Review

There are many, many among us who have been charmed by convenience while unknowingly slowly sacrificing quality. I have seen seasoned audiophiles poke fun at those of us who insist on having our music wherever we go, claiming soon those individuals will no longer be able to differentiate between music and hitting a bucket with a wet mop. I take some issue with this point of view because I love music, and I love it with me, 24/7.

I firmly believe the vast majority of individuals with white earbuds attached to their external auditory canals, can very much indeed tell the difference between higher and lower fidelity sound, they’ve just never had the opportunity! Enter Lyngdorf Audio’s new, fully digital integrated stereo amplifier, the TDAI 2170. Priced as a quality midlevel component, Lyngdorf Audio aims directly at the “iPod Generation” with a clean, adaptable user interface and uncompromising technology packaged in an elegant, familiar design. In Lyngdorf Audio’s attempt to show a new generation of 20- and 30-somethings how music is meant to be heard, they created a component so well executed it also lays waste to many so called “high-end” components costing multiples of its price.

Design of the Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier

Aesthetics

I cannot remember ever giving the packing of an electrical component much thought. Most modern electronics come well packed with plenty of molded Styrofoam, plastic sleeves, and double boxes to prevent noticeable damage to the contents. When the TDAI-2170 arrived there was not the usual small shift that one hears when something heavy is surrounded by Styrofoam and moved about; opening the outer box revealed its silent secret. The integrated amp was suspended between two sheets of clear, thick (and quite resilient) plastic film, not unlike a thick version of kitchen plastic wrap. These two sheets were themselves each attached to a cardboard square frame that occupied the perimeter of the box, each ½ the box’s height, positioning the two films as a “sandwich” of sorts.

This rather unusual design resulted in the 18lb integrated amplifier “floating” inside the outer box with several inches between it and the nearest side. The plastic film acted similarly to a rubber band to dampen any shock the unit incurred during transit. In speaking with Claus Glaesner, CEO of HTP USA and head of US distribution for Lyngdorf Audio, apparently in transit the TDAI-2170 can fall from 8 feet and land on any surface, at any angle and not sustain damage, physical or otherwise. Little did I know this seemingly unnecessary, but clearly over-engineered detail would serve as a prelude to the dogma of Lyngdorf Audio.

The chassis itself feels overbuilt and bombproof solid. Think Sherman tank construction with Ferrari finish. Needless to say, the TDAI-2170 feels quite substantial given its rather compact size.

Lyngdorf Audio calls the TDAI-2170’s design “modern Industrial” composed of matte black aluminum and black glass.

I call it clean, simple, and sexy! Its design keeps in step with previous Lyngdorf Steinway products. If you are unfamiliar their designs, it has a similar aesthetic appeal as Bang and Olufson or even Apple.

The face is clean and elegant, and unlike many components laden with rocker switches, dials, and buttons, the TDAI-2170 only two dials that adorn the face, one fairly small that serves to select the input and the other rather large (spans nearly the entire height of the chassis) to control the volume. Much like the ingeniously designed packing, the volume control was not simply produced, but feels crafted, like someone actually cared what it felt like when you turned it. The dial has weight and inertia to it, with a smooth glide – no “steps”, clicks, or cheap, hollow knobs here my friends! The use of just two dials also felt very familiar; it reminds me of an iPod of sorts.

Initially, the display was fairly unreadable from traditional listening distances, and I must not have been the only one to call the company about this seemingly small (pun fully intended), but functionally important detail. Not long after I asked Claus about this, a software upgrade was released which corrected this. Users will rejoice in knowing updating the software was exceedingly easy to do; no connecting to the Wi-Fi, no running Ethernet to the chassis, simply download to a USB flash drive and plug it into the back! The TDAI-2170 recognizes its update files and automatically extracts and installs them.

Functionality

From a functionality standpoint, the TDAI-2170 is modular, expandable and customizable. Rather than taking the all too common approach of saying, “Here is what you need.” Lyngdorf Audio chose the high road and instead asks, “What do you need?” The TDAI-2170 is available with several options so the listener can truly add only what he/she needs.

The “stock” TDAI-2170 comes with all the internal software, inputs and outputs one would expect from a two channel integrated amplifier, with digital and analog inputs, well-built 5-way binding posts, etc. However, should the need/desire arise, there are an additional three modules that can be ordered with the TDAI-2170: an audiophile USB board, an HDMI board, and a high-end analog board.

Arguably the most useful of the trio is a USB (type B) input. This allows the user to then connect the TDAI to any digital audio source, streaming device, or directly to one’s computer for playback high-resolution audio. With the USB board, the TDAI-2170 will handle up to 32-bit resolution and sampling frequency up to 384kHz. It will also handle native 2.8MHz and 5.6MHz DSD content as well (DSD64 and DSD128 respectively). I found this input was nearly essential, as all of my hi-resolution audio files are stored on my computer and the cable made for a “no muss, no fuss” connection. Keeping with the unbroken digital path mantra, this connection did indeed produce the best sound from the TDAI-2170.

With the optional HDMI 1.4 board installed, the TDAI-2170 becomes a ridiculously adept control center for an existing complete system as well. This module brings with it 4 HDMI inputs and an output enabling you to connect a Blu-ray player, satellite/cable box, and media player (with an additional input for whatever else you may have) with only one cable going to the TV. It is fully CEC and ARC compatible as well.

In an interview with Flemming Smith, Sales Director for Steinway Lyngdorf, I asked, “Why the inclusion of an HDMI module?” It almost seems a bit sacrilegious to add a video module to not just any audio component, but a dedicated TWO-CHANNEL audio component! Gasp!

Flemming’s first comment was on the HDMI cable itself, “HDMI is NOT just for video! It has some of the best audio transmission capabilities of any cable today.” His second comment struck a chord with me, “Today its all media . . . our TV finds radio stations and we watch movies on our phone; it is no longer divided into music, radio, TV, etc. This newer way of thinking creates an interactive experience. The user can determine if the TDAI will be used for high end two-channel audio or as an elegant receiver.” He was right. The traditional idea of what brought us music versus video is no longer entirely correct. I use my TVs more or less as the GUI to access data, regardless of whether or not the end result is video.

Flemming also commented that with the TDAI-2170, you no longer have to spend additional money on speakers if you already have a sound bar. Lyngdorf Audio has included their proprietary room correction software, “RoomPerfect”, with the TDAI to ensure it plays very nicely with sound bars and makes them sound at their best, despite being placed in traditionally “bad spots” (i.e.: flat against a wall and frequently at less than optimal height).

The third available module is a high-end analog input board. It has three sets of RCA right and left inputs, which while nice, on their own does not warrant the additional cost of the module, but what does is a set of fully balanced XLR inputs. Now your turntable and phono amp can join the party.

I thought this was a particularly wise move on Lyngdorf Audio’s part, rather than just focusing on bringing the iPod generation into the high end audio world they chose to be inclusionary rather than exclusionary. “We wanted to make sure you could hook up ANY source to the TDAI-2170 and it could handle it. And since some of the best source material is in the analog domain, we wanted to be sure to include the ability to handle this format.” said Claus during one of our discussions.

The TDAI-2170, as the name suggests, puts out 170 watts per channel to two channels into 4 Ohms with both channels driven. Although it is technically a “Class D” amplifier, it would be a mistake to assume this is simply a high-end version of a traditional “Class D” amplification.

The topography of the Lyngdorf Audio TDAI-2170 is true “fully-digital” amplification, not traditional class D. In the TDAI-2170 (using digital inputs) the signal never leaves the digital domain until the final output stage where it converts the PCM signal to PWM output, a relatively simple task.

Many of our readers are well versed in the various modes of amplification, but for those who have not committed our Secrets Primer on “Amplifier Class of Operation” to memory, here is a brief introduction to class D amplification.  I feel it is of great importance to understand how the Lyngdorf Audio TDAI-2170 is fundamentally different from other class D amplifiers.

First, class “D” amplification does not stand for “digital” amplification; although this misnomer has worked its way into our culture so thoroughly I hear it in almost every audio discussion and see it on nearly every audio blog/board. “D” simply happened to be the next letter in the alphabet when it was being defined as a type of amplification. (Yes there is a class “C”, but it has characteristics that make it unsuitable for audio signal amplification and finds most of its use in radio frequency amplification realm.) Class D amplifiers are also referred to as “switching” amplifiers, meaning the transistors (commonly MOFSET) in the amplifier operate as switches (fully “on” to fully “off”) instead of linear gain devices, as in analog audio.

Second, “digital” amplifiers (with very few exceptions) aren’t totally digital. They actually receive their signal in analog form, then convert it to digital so it can be manipulated/tweaked/caressed, converted BACK to analog, amplified, and sent to the speaker terminals. The more the signal is manipulated, the less and less it sounds like the original signal. Since we really only want the original signal amplified, this causes some problems.

While there are many faults inherent to class D amplification, I will limit this discussion to the largest faults, as there are books dedicated to the subject. In broad strokes, the timing of the switching in class D amplification is the largest source of audible problems, with “dead time” being particularly guilty. Dead time is the time when both the + and – transistors are “off” and no signal is conducted. Dead time in the tenths of nano-seconds can generate in excess of 1% Total Harmonic Distortion (THD). Moving from 40ns dead time to 15ns dead time can drop the THD from >2% to <0.2%; clearly dead time needs to be as short as possible to create an accurate, low-distortion output signal.

So a faster clock would be highly desirable? Yes, up to a point. If the switching is faster than the actual transistors can move between fully on and off, you run into the transistor being switched off still conducting when the transistor being switched on starts conducting – resulting in a short.

As I alluded to above, timing also plays a role in the transistors themselves. The amount of time each transistor spends going between fully “on” to fully “off” can adversely affect the sound and greatly shorten the life of the amplifier itself. This transition creates a state in which each transistor has significant resistance, which produces significant heat. Because class D amplifiers were not designed to handle excessive heat, this can cause significant damage to the circuitry.

But better timing in amplifiers, much like in its wrist bound brethren, is not cheap, nor is it the best way for mass marketed class D amplifiers to deal with high THD.

Far and away the most popular method of dealing with some of these inherent errors and improve the noise of the amplifier is by the use of a negative feedback loop. Negative feedback is a method used to correct for the non-linearity of an amplifier by feeding the output waveform of the amplifier back into the input stage enabling the internal circuitry to correct for deviations caused by the pulse-width modulator, output stage, supply voltage, or any internal source of audio distortion. As more and more negative feedback is generated, the THD drops further and further. This sounds like a great idea, and it is . . . to a point. Unfortunately this also amplifies higher order harmonics that may not have been audible previously but now are able to be heard. So while the specs may show an unbelievably low THD, the amplifier itself does not sound anywhere close to perfect; a classic example of theoretical perfection resulting in real world failure.

To Lyngdorf Audio’s credit, rather than providing a mechanism to compensate for inherent problems with mass-market class “D” amplifiers, they went to the source of the problem(s) . . . and there are many.

According to Lyngdorf Audio, they have developed a circuit architecture that is free of global feedback.

For starters, the internal clock used in the TDAI-2170 runs at 400kHz, not just several multiples of the oft used 20kHz (supposed upper range of human hearing), but more than an order of magnitude bigger! This combined with custom, high quality (not to mention fast) transistors nearly eliminates the biggest source of distortion, timing. They also isolate each component to limit the impact each has on the other. Because of this quality of design and build, the TDAI-2170 has NO feedback, and thus no need for a feedback loop! Thus the proverbial dog can stop chasing its tail.

To demonstrate this lack of feedback, Claus eventually convinced me to do something against all reason. He wanted me to have the TDAI-2170 actively running a signal, press “stop”, put my ear up to the speaker, and quickly turn the volume all the way up. After a brief moment of being convinced I had just gone deaf, I realized what had happened . . . because the TDAI has no internal sources of noise, when there is no signal being amplified there is simply, nothing. This example illustrates the (very near) technical perfection of the TDAI-2170 as an amplifier and serves as the backdrop to one of the best, most enjoyable, listening experiences I have had.

Lyngdorf Audio also recognizes the importance of combatting the “Loudness War.” Not only does this phenomenon result in crazy volume swings between different tracks, but also degrades the music itself. All converters, DA, AD, or otherwise cannot process signal above 0dBFS, and that information gets clipped (not included in the output signal). To prevent this loss of audio information Lyngdorf Audio employs “Intersample Clipping Correction” software. When the TDAI encounters a signal that extends above 0dBFS, it upconverts it to 200kHz, identifies what peak should be there, calculates it and restores it. The TDAI-2170 then reduces the loudness of the entire track by the difference between the peak that WAS clipped and 0dBFS. All of that happens in real time before the signal reaches the amplification stage.

The top bar in Figure 4 shows the clipped output waveform produced in other converters and the bottom shows the TDAI-2170’s reconstructed waveform with the entire audio signal intact, but with an overall reduced amplitude (volume).

I did notice a slight but perceptible decrease in volume overall during my time with the TDAI-2170. In my interview I asked Flemming if he thought listeners would initially be turned off due to the apparent loss of volume. He chuckled a bit and replied, “The reduction in overall volume is not noticeable to most people, but the reduction in compression is noticeable to almost everyone.” It may have been for kicks, but Lyngdorf Audio included a setting on the TDAI-2170 where it would display how clipped the audio signal was before processing, which I found strangely entertaining.

Setup of the Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier

While I have not personally set up many integrated amplifiers, the ones I have did not have room correction software. In my mind room correction software was always associated with multichannel audio, which required a receiver or pre/pro, most of which come with the latest flavor of Audessy, Dirac, ARC (in Anthem’s case), etc. I always figured you wanted your main speakers to sound their best in a given room you would move them and tweak them until you found the best position for them. Or at least this is what I have done for two-channel audio.

Lyngdorf Audio recognizes two very important and nearly universal truths: 1) 99% of the time we cannot control the dimensions of the room or what it is made of, but can control where the speakers are placed (to varying degrees) and 2) the room around the speakers probably has the largest impact on the sound heard (except for the speakers themselves). So while performing room correction measurements is not a new thing for me, performing them for a dedicated 2-channel system is.

The room correction software the TDAI uses is called “Room Perfect”, and claims to make your speakers “sound exactly as the manufacturer intended them to, not the way your room’s limitations make them sound.” A bold statement to say the least. Before I had actually used the “RoomPerfect” correction software I was skeptical at best; sure it could be good or even great, but perfect? In a discussion with Claus Glaesner over the name “RoomPerfect” he commented “We didn’t name it “RoomGood” or “RoomBetter” because it isn’t! It’s perfect!”

To achieve said sound, there is only one prerequisite (and one I’m sure most would actually like): place your speakers as close to the wall as possible to reduce the delayed reflections from walls.  According to the Lyngdorf Audio website, “whether used with full range, satellite, in-wall, or on-wall speakers, the TDAI-2170 is the perfect choice for any brand or model on the market.  Because of its unique technologies, the long-contested challenge of speaker placement no longer compromises performance.  On the contrary.  Simply place your speakers up against the wall to get the least amount of damaging reflections.  From there, RoomPerfect will adapt the speaker to the room and remove any unwanted bass boom.”

The theory is the fewer delayed reflections around the room, the easier it would be to account for them in the software. Even without taking the test microphone out of the box I knew I already had a problem. My reference speakers are a pair of highly upgraded VonSchweikert VR-7SE MK2’s; they are so modified the model ID plate reads: “VR-7SE MK3 #001”. Albert VonSchweikert originally built the pair for himself, but did not meet the WAF (Wife Acceptance Factor). While his modifications made for mind-bending audio, they also made for rather heavy (~500lbs each) and rather stable (spiked to my home’s foundation) speakers. And while I could not move them against the wall (or anywhere without some serious help for that matter), I could turn off the rear ambience driver. As I mentioned before, for two channel listening I had found the ideal spot for my speakers and assumed I would not have to move them to any significant degree . . . ever.

The TDAI-2170 includes a microphone and cable as most companies do for taking room measurements, but that is where the similarities end. The microphone is an honest to goodness real calibration microphone one might find in a professional calibration kit. The provided cable is a balanced XLR cable, not just a long version of cheap headphone cables typically supplied. Audiophiles rejoice! As if that were not enough, Lyngdorf Audio also included a professional microphone stand, a welcome treat from having to find your camera’s tripod (if one even exists) and finagle the individual legs to accommodate being on a couch, over a table, on the floor, etc.

All this is to say Lyngdorf Audio is serious and cares a great deal about the sound you hear from their products, and believes the process for obtaining said sound should be as clean as possible. The actual room calibration was the simplest and fastest I have ever performed.  The calibration requires you first to choose a single position for the microphone as the “focus” position.

For subsequent microphone placements, unlike other software where you are asked to be perfectly quiet and place the microphone in specific locations around the room, here you are asked specifically NOT to care about where it’s placed. In fact, they encourage you to take measurements near the ceiling, the floor, high, low, between the speakers, etc. so the TDAI-2170 gets to understand your room, in all its faults. It only took 4 locations to get 95% “room understanding” and 7 to get 99%! Last I checked needed a minimum of 9 locations to get anything close to (what I previously thought was) descent correction for the standard software included in the majority of pre/pros and receivers.

The menu layout in the TDAI-2170 follows suit with the clean mindset used throughout the rest of the component. Care was taken to make common tasks happen with the fewest movements. Switching from “global” room correction to “focus” room correction took two button pushes. Selecting a different input was a simple push on the remote, or turn of the smaller knob on the front of the TDAI-2170. Given the possibility of multiple inputs, Lyngdorf Audio made it easy to rename any of them without having to “drill down” 17 layers of menus, and made it easy to skip over inputs with no connection.

The Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier In Use

Honestly, I didn’t believe it at first; but after switching back and forth from the TDAI and my reference system (for which I used 20 mic locations to dial in) I can say for two channel audio the TDAI-2170 handily beat my system silly. The main reason for this piece of humble pie has to do with the absence of feedback alluded to earlier.

Many reviewers in both the video and audio realm (myself included) often refer to the absence of color or sound (where appropriate) as the “blackness” of a product, and the blacker the better. As the background gets blacker and blacker (more and more silent), you begin to hear things in familiar recordings you haven’t heard before, or at least couldn’t precisely identify. The Lyngdorf Audio TDAI-2170 was so silent it disappeared from my system entirely! Those readers who follow me on my quest for “audio truth” will recall I carefully choose my audio components to be as absolutely neutral and silent as possible; I want to hear what the artist meant to be heard, not what my system makes it sound like.

I listen to a fairly wide variety of music on a daily basis, so you may notice I do not stick to a single genre when reviewing. What you should garner from this review and the others I write, even if your musical tastes differ from mine, is over arching themes to components rather than specifics relating to any particular track.

Because my system and the TDAI-2170 use different volume scales, I used an SPL meter to ensure I was listening to both systems at the same level in order to avoid simply favoring the loudest of the pair.

One of the more unique groups I like is VAST, a rather esoteric ambient electro-rock band from Austin. The track “Don’t take your love away from me” clearly conveys the size of the space the band recorded in. While the “hollow-ness” of the sound isn’t subtle, it was more real through the TDAI-2170 than I had remembered. The notes from the upright bass came through clearly and its position became more defined. You could actually hear the fingers on the strings, not just the notes. To VAST’s credit, these elements were purposefully placed to add a level of emptiness that make the audience emotionally involved in the song. This was very apparent on the TDAI-2170, more so than on other systems I’ve heard.

I find Madonna’s “Sound of Goodbye” from the 1998 release of Ray of Light to be a very telling track that rapidly reveals a system’s ability to image and create soundstage. I love to play this track for “non-believers” who insist no system can create a truly “believable” soundstage beyond the width of the speakers. My system does this particularly well, so I was already expecting a wide soundstage. As the song began playing through the TDAI-2170, there was a moment my brain thought, “How is this playing through my surrounds?” That instant is when you know you have something special: when you can fool your brain, which knows only the main speakers are connected, into thinking otherwise. However brief that moment may be matters little because the realization that it happened at all is startling and slightly unsettling.

Elizabeth Fraser lent her ethereal vocals to Massive Attack’s “Teardrop”, originally released in 1998 on the album Mezzanine. Her airy notes were haunting, put into perfect space and time by the TDAI-2170. The piano notes were as believable as if one had been in the room and again placed deftly into the soundstage by the TDAI-2170. This amazing detail and clarity layered with the grainy, raw hissing and popping from the background “turntable” made for a rather emotional listening experience.

Possibly the most impressive display of the TDAI’s prowess came during the Smashing Pumpkin’s “Appels + Oranjes” off of the 1998 album Adore. “Appels + Oranjes” contains only electronic instruments and front man Billy Corgan’s vocals. I find the tack quite haunting; this is perhaps magnified by the isolation of Corgan’s whiney lyrics, as there is no other “real” instrument to compete with. On the TDAI-2170, I no longer had a track, but a live solo performance! There is a slight drift up and then down in tone as Corgan languishes over the last syllable in the line “It came from your thoughts, your dreams and visions,” that sounded more life-like than I’ve ever heard before. My listening notes very accurately recount the experience: “Speakers disappeared entirely. Very striking. Billy Corgan’s whining voice came through with utmost clarity . . . strangely more real than on other systems.”

Releasing their first full-length album Sirens just this past October, Gorgon City’s English dynamic duo is relatively new on the music scene. The fifth track on the album, “FTPA”, is my favorite for a number of reasons. There are soulful vocals, deep bass, and it finishes with a beautiful trumpet solo. I heard the group perform live at TomorrowWorld 2014 this September in Georgia, and very rarely does a song performed on a small stage, with 11 other stages going simultaneously, stop people in their tracks as this one did.

There is clearly a difference in live music at a festival and the quiet of a recording studio, but it does give you some sort of baseline to go off of. Once again, the TDAI-2170 provided Über-clarity at any listening level, specifically highlighted by the trumpet solo in the last 45 seconds of the track. The miniscule clicks of the trumpet valves as the musician seduces the notes from the brass are ever so quiet, but clearly recorded. This resolution is a direct result of the TDAI’s absolutely black background, thus uncovering these faintest of sounds.

Were there faults to the TDAI-2170? Maybe. On occasion I felt the TDAI-2170 didn’t extend all the way down to the subterranean bass levels my system could dive to, but this was not an easy pickup. Only after listening to the same tack over and over on both systems, and bouncing frequently between them did I notice this. Even then it was limited to a few sequences in the rare track designed to push limits of bass. Some of my dearest friends (with very good ears) did not think there was any difference in bass, and if there was, it was so miniscule it would only be noticed on certain test tracks and only if you were looking for it.

The only other critique I have for the TDAI-2170 is less of a real world issue and more of a testing issue. At 170 Watts per channel, the TDAI is capable of driving most speakers at regular listening volumes with enough headroom to be plenty dynamic. However, when listening to demanding rock or electronica in my theater/listening room (10’H x 15’10”W x 23’D) at concert levels, the TDAI-2170 couldn’t match the dynamics and attack of my reference system. Although at those levels I’m more or less asking, “Can it do this?” rather than enjoying the music. Even then, the music sounded better overall on the TDAI-2170.

Conclusions about the Lyngdorf Audio TDAI-2170 Fully-Digital Integrated Amplifier

At a base price of $3,999, the TDAI is by no means inexpensive. I would however challenge any integrated amplifier (or separates for that matter) to perform at the TDAI’s level in the real world with the clean elegance it pulls off. Claus Glaesner refers to the TDAI-2170 as “High-end audio for the iPod Generation.” I would call it simply “High-end for everyone.”

If I had to describe the TDAI in one word it would be “clean”. The design is clean, the interface is clean, the sound is clean . . . the entire execution of the package is clean. Adaptable would be a close second. Want to run your high-resolution files from your computer? Got it covered. Really wish you could use it as a receiver? Poof! HDMI board. Need to include your turntable and phono with balanced outputs? Done. If it exists in the audio realm, the TDAI-2170 can play it. The “RoomPerfect” software is exceedingly easy to use and provides outstanding results. So good were the results with the TDAI-2170 and its software I used it exclusively when listening to two-channel audio while it was in my possession.

In 2008 Secrets colleague Michael Galvin reviewed Lyngdorf Audio’s SDAI-2175, one of the TDAI-2170’s predecessors, and was amazed at the shear absence of any sonic signature. I think he would happily agree the TDAI-2170 carries this lack of signature to a new level! Rather than re-invent a way to describe the shear silence and profound neutrality the TDAI delivers, I’ll just use his words: “(it) disappears better than most audio components are able to do anything”.

So silent is the TDAI-2170, I highly recommend Lyngdorf Audio look into trademarking the background silence in audio media and rename it “black-ground.” It is truly the most silent background I have ever heard, on any system, of any kind.

In the end, it is really what Lyngdorf Audio eliminated from the traditional Class D amplifier that makes the TDAI stand above others. By going to the source of “noise” in the amplifier and solving each problem individually with no short cuts or bypasses, Lyngdorf Audio has redefined what a “Class D” amplifier should sound like – absolutely nothing.

“Music is the space between the notes.” – Claude Debussy

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Parasound Halo JC 3+ Phono Preamplifier Review Highlights

Secrets of Home Theater and High Fidelity has long been a leader in reviews of all categories of home theater and audio gear. This review covers the updated phono preamplifier from Parasound’s premier Halo line. Parasound’s uncompromising approach has resulted in a truly stunning piece of gear.

Parasound Halo JC 3+ Phono Preamplifier Highlights Summary

• The Parasound Halo JC 3+ Phono Preamplifier is designed to accommodate any phono cartridge
• A rich, detailed sound with subterranean bass ability
• A truly “what-more–could-you-ask-for” component that impresses at every turn
• Molded panel end caps seem out of place on a reference-level product

Introduction to the Parasound Halo JC 3+ Phono Preamplifier Review

Seven years ago, Parasound asked legendary designer, John Curl, to create a phono preamplifier for its Halo line. The design goals were ultra-high performance and low noise, in the spirit of Curl’s legendary Vendetta phono preamp. Three years later, Parasound introduced the JC 3 phono preamplifier. While very well received, the JC 3 did not offer much in the way of loading adjustments. For MC cartridges, there were two resistance settings, 100 ohm or 47k ohm. Some people probably didn’t care about that “limitation”, but others undoubtedly did and stayed away. With the arrival of the JC 3 +, loading limitations are history and instead of compromising it, performance was actually improved. Parasound tweaked the phono module board, which has resulted in an improvement from 75dB to 87dB in the MC signal-to-noise ratio. Parasound claims that significant improvements were also made to the power supply. The price increase over the JC 3 is $645.

Design and Setup of the Parasound Halo JC 3+ Phono Preamplifier

Phono preamplifiers come in a wide variety of shapes and sizes. The JC 3+ makes its first statement via its generous size and weight. Pry it open and you’ll start to realize why.

As you can see, the internal layout features three zones of isolation. Most strikingly, the left and right gain modules reside in their own aluminum housings. The first time I opened it, the JC 3+ struck me as something I’d need Jack Bauer to defuse. It certainly looks expensive.

The JC 3+ also has its own built-in AC line conditioner as well as a dedicated setting (via the front panel) for mono records. At the rear panel, you will find that each channel has a three-position switch for cartridge loading. The options are 47k MC, variable MC, and 47k MM. The variable MC loading range is 50-550 Ohms. For my Dynavector 20X2L, I selected variable MC and used 100 ohm. You also have the choice between single-ended or balanced output. I used the single-ended outputs exclusively.

The Parasound Halo JC 3+ Phono Preamplifier In Use

What most surprised me after I invested more and more money into vinyl playback was the jump in dynamic capability. Just when I thought I had my system pretty dialed, the JC 3+ took it to another level. Not night and day, but noticeable, important differences for sure. The most striking thing was simply more attack. Constant attack, nuanced separation of individual notes, speed, speed, speed, and bass. A really good example, one I returned to over and over throughout the review period, is Heart’s 1976 debut, Dreamboat Annie [Mushroom Records (MRS-5005)]. I don’t ever remember thinking this album was anything special, but that’s probably because I never actually heard much of it before. Through the JC 3+, Ann Wilson’s vocals have an urgency that is almost disorienting, especially on the familiar “Crazy on You.” The first side of the record is so strange and interesting to me. It seems to alternate between the hard rock of the 70s (“Magic Man”) and 60s Psychedelia (“Soul of the Sea”). There is some moog synthesizer, odd combinations of acoustic and electric guitar, bells, ocean waves, banjo, and probably much more. And again, that’s just side one!

Even though I don’t have many mono records, I was curious about that button on the JC 3+, so I grabbed The Village Green Preservation Society by the Kinks [Sanctuary NPL-18233]. I never tire of this album, especially side two. Most memorable to me is the final track, “People Take Pictures of Each Other”, in which the Kinks predict (and mercilessly indict) Instagram, 40 years before its creation. With the JC 3+ mono switch activated, the vocal and instrumentation seemed slightly more focused. When I disengaged it, the sound seemed a bit washed out and diffuse, which was especially noticeable on the vocals and keyboards. In terms of dynamics, this album is not a fireworks show, but it does give the JC 3+ to shine in a different way, by showing you how dead silent background noise can be on a clean record.

I don’t think there is a day that goes by that I don’t listen to at least one side of a 90s-era hip hop record. One of my favorites is Diamond D and the Psychotic Neurotics’ 1992 opus, Stunts Blunts & Hip Hop [Chemistry Records]. While I fear this record is digitally sourced, what the JC 3+ provides in the nether regions is very impressive. I had really only one thought: damn, that’s thumping! And while there’s not a lot of nuance to the drum tracks, the important thing is what the JC 3+ manages to dig out: the horn blast samples, the telltale 90s’ scratching, and the overall fun, wild vibe of the album.

Conclusions about the Parasound Halo JC 3+ Phono Preamplifier

Three grand for a phono preamplifier is, in my view, a ton of money and I would never take lightly recommending such an expensive component. However, believe me when I tell you the JC 3+ is one of those rare products that justifies its ticket. In my system, it unlocked the promise of both the cartridge and the turntable, taking both to heights of resolution and attack which had been suppressed until its arrival. I don’t listen to vinyl nearly as much as I’d like to, but I’m confident that how the JC 3+ breathes life and energy into music is exceptional. After you’ve experienced it, it seems impossible to take even the smallest of steps backward. It invigorates everything it touches. The extraordinary thing is that every time you listen, it feels special and reminds you that this strange alchemy called audio sometimes fulfills its promise.

Associated Equipment:
Spendor D7; Kef LS-50, Naim Supernait 2, Naim NAC-A5 speaker cable; Well Tempered Labs Simplex turntable; Dynavector 20x2L moving coil phono cartridge; Musical Surroundings Phonomena II phono stage; Audience Au24e (low) phono cable; DH Labs Air Matrix interconnects; Audience PDC power distributor; Naim Tibia and DH Labs Encore power cables.

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NAD C 510 Direct Digital Preamp DAC Review Highlights

Is your trusty old stereo setup looking for a minor makeover? Are you wanting to play more of those high resolution audio files from your computer or Blu-ray player through to your big speakers and revel in all the high bitrate sonic goodness? Boasting high speed digital processing and HDMI connectivity, the NAD C 510 aims to bring your traditional two channel music system into the twenty-first century.

Based on a similar concept as the well regarded M51 Direct Digital DAC in NAD’s Master Series line, the C 510 wears a more traditional looking NAD suit. And in some ways, more than the Master Series, it reflects NAD’s traditional values and reputation more clearly, which is a simple understated design with absurdly capable real world performance.

In my two channel stereo setup the C 510 made a welcome and noticeable improvement to my musical enjoyment and opened up some additional connection possibilities that I, up to this point, had not yet explored.

NAD C 510 Direct Digital Preamp DAC Highlights Summary

• Exclusive use of the CSRA6601 chip as a DAC
• Incredibly detailed and well resolved sound, without sounding lean or etched
• Can be used as a standalone DAC or as a digital preamp with volume control (digital domain)
• HDMI connectivity and video pass through
• Single ended and balanced outputs
• Will not decode native DSD bit stream directly

Introduction to the NAD C 510 Direct Digital Preamp DAC Review

During my first ever trip to CES in January, 2015, one of the things I noticed, while auditioning the various audio related rooms and booths at the Venetian Hotel, was the crazy number of DACs that are now out there on the market. Maybe I’ve been under a rock for the past little while, but I don’t recall DACs being so talked about and hyped since about 15 to 20 years ago. At that time the discussion was about how inadequate the decoding in your standalone CD player was and how this extra little “black box” would bring back all the missing life to the digits on your little silver discs.

As the years went on, CD players got progressively better, focus shifted more towards home theater, and with the progressive advancements of portable audio and the arrival of the MP3 format, I think the subject of DACs became more of a concern for the committed and, more often than not, well-heeled audio enthusiast.

Fast forward to today: high resolution audio files are now available for download, while storage media has increased in size and has become much more affordable. The idea of streaming your media around the house in the best quality possible is a very doable proposition. Also, computer audio, as a serious method of musical enjoyment, has come of age, and audiophile media such as high resolution Blu-Ray audio is becoming more prevalent.

I mean, serious on-the-go audiophiles are buying portable DACs the size of their mobile phones to carry along with them, strapping them to their players with rubber bands! If ever there was a time where a digital hub of “sonic awesomeness” was needed to make all your (at home) media sound its best, it is NOW. Enter the NAD C 510.

The Design of the NAD C 510 Direct Digital Preamp DAC

DACs (Digital to Analog Converters) are typically meant to do one job. That is, take the digital information from a given transport medium and reassemble said information into a pristine analog waveform. That waveform will eventually be amplified to come out of our speakers as music, reach our ears and, hopefully, be able to move us in the intended way.

From a circuit design standpoint, most DACs, save for some of the more esoteric models, will usually start with a main converter chip sourced from an established manufacturer. Those chip makers tend to be one of the following: Analog Devices, AKM, Burr-Brown, Cirrus Logic, ESS and Wolfson.

Once a digital core has been selected, the surrounding electronics such as the power supplies and the analog components are then developed and honed to maximize the core chip’s potential performance.

When Secrets Editor-in-Chief, Dr. John Johnson reviewed the NAD M51 Direct digital DAC back in 2012.

(he noted how NAD had gone the unusual route of designing a custom decoding solution instead of starting off with a ready-made chip to design around. The core chip in question is the CSRA6601 and was co-developed with Zetex Semiconductor (the technology is now owned by Cambridge Silicon Radio) and was originally part of a chipset produced for switching power amplifiers. In this case, part of that original chipset has been repurposed for use solely as a DAC chip.

Visually, the NAD C 510 eschews the brushed metal look of the well regarded Master Series line for the more traditional minimalist look of NAD components of yore. There are less hard corners and more rounded edges nowadays, but the NAD look is unmistakable. The front panel is very simple and straightforward with a blue dot matrix display taking up a fair share of the face.

The display clearly spells out which input is in use and the sample rate that the input is being fed. Basic settings options and selections are visible through the display as well. Moving a little to the right we find a pair of buttons that are used to cycle through the various inputs. Moving to the right some more, we encounter a rotary dial that operates the digital volume control. The volume can be set to a user defined fixed level for DAC use or a variable level, so the C 510 can operate as a digital preamp. Lastly, the power button is located on the far left.

On the back side, from left to right, we have both balanced and single ended analog outputs, an AES, a coaxial and an optical digital input, followed by a USB input for computer hookup. The next two inputs are a rare sight on an audio only component, but I think will start being more prevalent in years to come, those being a pair of HDMI inputs. An HDMI output comes next, allowing unmolested video pass-thorough to a display device. A USB socket marked “Upgrade” is next, presumably used for firmware updates and the like. Lastly there is an RS 232 serial port that is AMX and Creston compatible, a 12 volt In and Out trigger jack and an IR extender jack.

The remote control provided with the C 510 is an all plastic unit that is nicely weighted and feels good in hand. It’s got all the control buttons you would expect for an audio preamp, plus learning capability to control up to three other components comfortably. Pressing the DIM button allows the DAC’s front display to be turned off and then a choice from 5 levels of intensity. Nice! Positive and reverse polarity selections are also available along with adjustment of the fixed volume level through the Setup menu.

Out of the box, the C 510 had a fixed volume level of -20 dB. For my listening, I adjusted the fixed volume level to -3 dB to, more or less, match the incoming level of a couple of other DACs and CD players I had on hand. This allowed me to have multiple units hooked through my preamp, with the ability to switch between sources, playing back the same material, with just the turn of a dial.

Setup of the NAD C 510 Direct Digital Preamp DAC

For the majority of my testing, I had the C 510 hooked up to my two channel system, serving primarily as a DAC. I did experiment a little with it as a preamp, using the adjustable volume, and while it works quite well as advertised, it was just more practical in my setup functioning in pure DAC mode, adjusting the master volume via my existing preamp. I had also just obtained a new OPPO BDP-103 universal player for Christmas and it allowed me to make good use of the C 510’s HDMI inputs.

As a matter of fact, the new player never made it into its intended spot in my home theater. So convenient and good sounding was the pairing of the OPPO with the NAD that it may never leave my studio! The OPPO allowed me to hook up an external USB hard drive full of music files, and access them with a simple and quick navigation menu on my studio TV. It was a much better solution than the old Western Digital media player that I had been using previously.

Associated equipment in the review: OPPO BDP-103 Universal player, Onkyo DV-SP1000 universal player, Bryston BP 25 preamplifier, Marchand XM 16 electronic crossover, Marchand BASSIS parametric equalizer, 2 Carver TFM 55x power amplifiers, BESL (now Bamberg Audio) Series 2 MTM monitor speakers, twin custom sealed subwoofers with 15 inch Dayton Reference HF drivers.

The NAD C 510 Direct Digital Preamp DAC In Use

I’m just going to say up front that I really like the sound of the NAD C 510. Besides the fact that it’s just neat to see a company go in a different direction when designing a piece of core audio gear, I think that in NAD’s case, it’s paid some sonic dividends, resulting in a very stellar sounding component. Through my comparisons with other DACs and other players I had on hand, the NAD revealed itself to be a very honest and transparent reproducer of sound.

Its ability to mine every last little bit of detail from my collection of spinning silver platters and hard drives was very, very impressive. I found myself noticing more details and subtleties in songs that I’ve heard countless times, and I found that I could listen at louder volumes more cleanly with the NAD in my system.

For myself, with other DACs and players that I’ve used, there has always been a “ceiling” where the music isn’t uncomfortably loud, but it becomes uncomfortable to listen to for an extended period, meaning too much distortion. The NAD sounded better and better to me, the louder I turned it up. Don’t get me wrong, it sounds perfectly great puttering around at low volumes as well, but wide open and at full “chat”, the C 510 just sings!

There are two other standalone solid state DACs that I’ve used in my system regularly over the past couple of years. One is the Audio GD Compass 2 based on the ESS Sabre 9018 chip, and the other, an ONIX DAC 25 based on the Texas Instruments PCM 1792 chip. I did some comparisons where I had the NAD and the two other DACs hooked up simultaneously through the various digital outputs (HDMI, optical and coaxial) on my OPPO player, and I would simply switch between preamp inputs to compare the same musical track.

Again, the NAD’s adjustable digital volume made it easy to equalize its output levels to the other DACs which were about identical to each other. A few other times I compared the NAD to each of the other DACs individually with the OPPO hooked to the C 510 with either the coaxial or the optical input.

Some of the music I listened to during my stint with the NAD:

“Rhythm and Blues” by Buddy Guy on CD is excellent recent vintage recording of a Chicago blues institution. Buddy Guy is in top form on this two CD set, and the C 510 helped to present a nice big soundstage and reproduced the boldness and power of his electric guitar with accuracy and detail to spare. This was one of those recordings that I expected to get harsh and fatiguing when I turned up the volume but, thankfully, no such thing happened. There was no edginess to speak of on any of the guitar or background horns, just clean, dynamic reproduction. Buddy’s voice came through with plenty of character, particularly on the more intimate tracks, while cymbals had just the right sheen to their sound, and bass delivery was tight and solid. The other two DACs did an admirable job with this CD set as well, but, in general, I felt the NAD gave me a cleaner presentation overall.

Steely Dan’s Pretzel Logic on Japanese import SACD is an excellent edition of this classic recording. It’s also one of the discs that I found sounded a little “tubby” when listening through the other DACs I had on hand. In particular, I felt the electric piano and drums sounded like they had too much upper bass, making the songs seem heavy and congested. This was not the case when playback was happening through the NAD. The C 510 brought out a level of clarity and detail that made all the music lighter and more “alive” sounding. Its sonic presentation also befitted the scrupulous production values that Steely Dan had put into those original recordings in the first place. The NAD C 510 does not natively decode DSD, so I needed to set my OPPO BDP-103 to convert the DSD bit stream to PCM before passing it along. The NAD accepted this at an indicated, down sampled, rate of 88.2 kHz. Having just experienced the plethora of DACs at CES, many of which touted their ability to decode native DSD (mostly though USB inputs), I inquired to Greg Stidsen, the Director of Technology and Product Planning for Lenbrook International, why the C 510 did not have this ability? He replied to me,

“Regarding ‘why no DSD’, when the DDFA part was in development, DSD was dead, dead, dead. We were ‘giving away’ SACD players at steep discounts at the time. Nobody wanted them. Now, if you have an SACD player that supports HDMI (like Oppo) you can play SACDs with the C 510 via HDMI (DSD converted to encrypted PCM). But the USB input does not support DSD streaming, unfortunately.”

The NAD does have the ability to be updated via firmware, but I received no indication as to whether native DSD decoding could be in a future update, or if it would be even possible at all with the current hardware inside.

“The Crossing” by David Elias is a direct to DSD recorded album done by the independent folk artist. The entire album consists of downloaded DSF files, available both in stereo and 5.1 surround. The files were played through the OPPO from a connected external USB hard drive and decoded by the NAD as 88.2 kHz PCM.

There is a vigorous debate going on out there as to the value of DSD as a recording medium versus PCM. Is there a discernible increase in sound quality with DSD, or is it just hype and are all these DACs that can decode native DSD just jumping on this latest bandwagon? A lot of this stems from the confusion of what exactly constitutes “Hi-Res” music these days and if we, as the consumers of it, know exactly what we are really getting, quality-wise, when we click the “purchase” button on various music sites.

From my perspective, the quality of the musical production (recording, mixing, mastering) makes far more difference to the final outcome than the delivery format itself. “The Crossing” is some of the most wonderfully recorded music that I’ve ever heard, folk or otherwise, and the NAD just rendered all the instrumental and vocal nuances about as perfectly as I could have wished, even at the down-sampled, encrypted rate I was getting.

The Very Best of Erich Kunzel and The Cincinnati Pops “Top 20” on CD by Telarc. This is an old standby for sheer musical dynamics. Telarc, as a label, cut its teeth making modern recordings that pushed the limits of what the compact disc format and your stereo set could reproduce. On less capable equipment, this CD will sound shrill and grating on a number of tracks. The dynamic musical swings will not get translated properly. Not so with the C 510. This album came across the best I have ever heard it. As I turned up the volume, the entire orchestra just became positively massive! Huge soundstage and all the instrument sections were easily discernible. Strings in particular had a lovely, smooth, yet detailed presentation. Bass, on a number of the tracks taken from sci-fi movies, was as powerful as all get out and it actually frightened my dogs!

In general, over the course of my audition time, the subjective impressions I came away with were that the ONIX DAC 25 added a little bit of a euphonic quality or “bloom” to music, similar to what people associate with a “tube-like” sound. This resulted in certain tracks sounding like they had an extra sense of space. The Audio GD DAC, by comparison, had a slightly more detailed sound but with a little bit of an accentuated upper bass that I noticed more readily on rock and electric blues music. The NAD, in turn, was very even handed with all manner of music that I threw at it. The C 510 sounded impeccably clean with no trace of noise that I could discern.

Conclusions about the NAD C 510 Direct Digital Preamp DAC

The NAD C 510 proved itself to be an excellent DAC through its entire residency in my stereo system. From its understated looks, to the plethora of connections (including HDMI with video pass through), and its custom decoding engine, the C 510 is more than capable to handle all your digital conversion needs.

Combine that with a built in volume control and a separate remote control and the NAD looks to be vying for a spot as the central digital hub of your whole system. I found the NAD’s sonic signature to be subjectively flawless to my ears. All I can say is that over the month that I had the NAD in my system, I really came to enjoy the way that it sounded. When I switched it out for either of the other DACs I had around, I simply felt that my music was missing something. To me, it neither embellished nor diminished any of the audible spectra. It simply gave me exactly what was there, all of it. And it did it in a manner that made me want to turn up the volume and get lost in the music.

At an asking price of about $1300.00, the NAD looks to be an excellent value in the current DAC market. It’s also somewhat unique in that I am only aware of maybe two other audio-only DACs that have HDMI connectivity. The only possible criticism I could come up with is its inability to decode a native DSD bit stream over HDMI or USB. With native DSD playback being the “it” thing at the moment, its absence on the NAD may turn some users away Note, however, that many high resolution music albums are available both in PCM format as well as DSD. So, if you purchase the NAD C510, get your music downloads in the PCM format.

Although the converted and down-sampled DSD files I played through it sounded good enough that, in reality, it may not make much of a difference. If that isn’t a deal breaker for you, then by all means audition the NAD C 510. I think you will find its pristine sound quality very addictive. I highly recommend it!

The author wishes to acknowledge the assistance of Senior Editors, Dr. David Rich and Robert Kozel, in the preparation of this review.

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NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier Review Highlights

NAD calls their best electronics the “Masters Series”. The preamp and amp under review here are in this class of components. The M12 preamp is a digital preamp and DAC. It is a very unique design that up samples all signals to a high bit rate and then the signal is never converted back to analog in a traditional sense.

The M22 stereo power amplifier is no less innovative. It features a hybrid digital/analog design based on the latest nCore® circuitry from Hypex. This little amplifier puts out an incredible amount of power with extremely low distortion.

These products produced a liquid, emotive performance with a balanced tonal palette. I believe NAD rightfully deserves to be considered a major contender in the high end arena due in large part to the wonderful performance of the M12 and the M22.

NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier Highlights Summary

• All-digital architecture
• Flexible, future-proof modular design
• Stylish looks
• Smooth, liquid sound
• Ultra low distortion
• Extremely powerful amplifier with plenty of headroom

Introduction to the NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier Review

NAD burst onto the scene in the late ‘70’s and early ‘80’s when they became something of a household name via a series of very affordable integrated amps, the most popular of which was the 3020. NAD sold a huge number of these amps and cemented their reputation as a high-performance, high-value brand. So I will forgive you if you still think of them as a mid-fi company. But it is high time to change all that and the M12 and M22 are in my mind nothing more than the most current harbingers of this new message.

I have had the pleasure to audition many of NAD’s cutting-edge products in recent years. In each and every instance, I became increasingly impressed how NAD’s products could go toe-to-toe with many of the industry’s most storied and popular high-end brands. Suffice it to say that I see NAD as the “real deal”.

Exhibits A and B in support of my case are the Masters Series M12 and M22 amp/preamp combo. These are ultra modern products that are predicated on the most up to date circuitry out there. They are also NAD products which means that they take their own path to achieve great sound in a beautiful and efficient package. The preamp is a modular design that can serve as your system’s nerve center for . . . well, for “ever” really, add that the amplifier can realistically drive any speaker in the world and you will be on your way to one amazing set up

Design and Setup of the NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier

The NAD M12 preamp is most accurately characterized as one of many products in a burgeoning category of “DAC/Preamps”. I say this because it does all its hard work in the digital domain. This includes volume control, subwoofer crossover, tone controls, etc. Digital sources remain in the digital domain while analog sources get converted to digital for manipulation. The signal never really gets converted back to analog, but instead is fed to a Class A buffer as a Pulse-Width-Modulation (PWM) signal on its journey to your power amplification component(s).

For this reason, NAD calls the M12 a “Digital Audio Hub”. In many ways, this concept appears to be the future of high end audio and not just from NAD but also from several other forward-thinking manufacturers out there.

In true NAD fashion, though, they take their own path . . . they march to the beat of a different drummer so to speak. Along these lines, the M12 operates with a native 35-bit word length. This isn’t a typo. The M12 doesn’t work at 16-, 24- or 32-bit; it really is “35 bits”. All sources are up-converted to 62-bit before the DSP functions are applied and then the signal is truncated back to 35-bit via a dithered process.

This is how the digital volume control can function without audible noise or any loss of musical detail that would be the result of truncating a 16- or 24-bit signal. It is a brilliant concept and is part of the reason NAD has enjoyed rave reviews of the products that are predicated on this concept not the least of which being John E. Johnson’s excellent review of the NAD M51 Direct Digital DAC that can be found here NAD M51 DAC Review. Please take a few minutes to read John’s explanation of the inner workings of the M51 and you will better understand how the M12 operates.

Another design and implementation concept that sets the M12 apart from its competition is what NAD refers to as their Modular Design Concept (MDC). The M12 unit has six bays available for upgrade and/or add-on modules. The stock unit comes with three modules pre-installed – the analog input card (3 inputs), a digital input card (optical, AES/EBU and S/PDIF over coax) and a USB input card (2 types) for full 24 bit, 192 kHz asynchronous inputs. (There is also a front-panel USB input.)

These installed modules can be upgraded via future releases of improved modules. But the NAD also has increased functionality available, particularly when compared to your more run of the mill competitors. This increase in functionality comes via a handful of optional MDC modules that are currently available or are in development.

One very interesting add-on module is an HDMI card which has 3 inputs and one output with video pass-through. This can be used for dedicated HDMI audio or for those who want to watch TV on their two-channel system. I did not evaluate an HDMI card in this review.

The other module that is currently available is a network audio module which is based on NAD’s BluOS system. I had one of these installed in my review unit. This card can be connected to your home network via Ethernet or WiFi and it also plays back aptX Bluetooth sources directly. This module is compatible with all the most popular online music streaming services as well.

I connected the BluOS module via WiFi then downloaded and installed the free NAD BluSound app to my HTC One phone. The system found all the music on my NAS server and I was able to play back even high resolution files wirelessly. I was really won over by this system which I will discuss in a little more detail later in the In Use section.

The backlit remote was fashionable and functional. I liked that its aluminum case had a comfortable trapezoidal cross section. The backlighting comes on when triggered by a motion sensor that sometimes was a bit reluctant to respond. All in all, though, the remote was compatible with the high level of performance available with this lovely NAD combo. (I found myself controlling the unit with my phone much of the time anyway.)

Two more quick notes about the M12 – it has internal bass management with dual (stereo or mono) unbalanced subwoofer outputs. It also contains IR repeaters and multiple 12V triggers. Thus it is compatible with advanced control systems.

Now let’s talk about the M22 stereo power amp. It has one very obvious peculiarity (to me, at least) – it is physically much smaller than the M12 preamp. I was going to be stacking these components in my rack and I debated for a few minutes if the amp should be on top or on bottom. I would up with the amp on bottom because it just felt right, you know?

NAD classifies the M22 power amp as a “Hybrid” design utilizing Nypex nCore circuit designs predicated on the UcD concept. According to a NAD white paper on the subject, “the UcD concept is a switching analogue amplifier with all parameters highly optimized to allow self-regulation.” The design ultimately allows 20 dB more feedback to be used which results in reduced distortion. NAD also claims UcD has “amazing characteristics of load invariance and high current capability.”

The M22 uses the latest generation of NAD’s PowerDrive technology which ensures up to 250 wpc of continuous power output with reserve capacity of up to 600W of dynamic power into a 2 ohm load. This PowerDrive circuitry is claimed to preserve the life in music while allowing the M22 to demonstrate wide compatibility with pretty much any speaker you may be using.

The M22 is DC Coupled throughout with no capacitors in the signal path. DC is rejected by way of localized negative feedback.

The power supply is an advanced regulated switch mode power supply which promises low noise and an energy efficient design.

Finally, electronic protection circuits eliminate speaker relays.

The M22 has balanced and unbalanced inputs, a trigger switch and rugged five-way binding posts (one pair per channel).

These products are quite solidly built with a modern, industrial appeal. The M12 in particular is very nice looking with its clean lines and two-tone case. The front panel has a large volume knob but the front is mostly dominated by the good sized touch screen display. You can use this screen or the fully-functional remote to access and control the tight menu structure.

I placed the M22 amp on bottom, connected it to the M12 preamp via a pair of balanced interconnects. I connected the 12V trigger for automatic turn-on of the amplifier. I also connected a Bluetooth antenna and a WiFi dongle to the BluOS module. I connected my Blu-Ray player, turntable, laptop and surround processor’s main channel outs to the M12.

I used a pair of satellite speakers with a single subwoofer for most of my critical listening. So I connected the satellites to the amp via banana plugs while connecting the sub to the unbalanced output of the M12. I used the internal crossover and trim functions for bass management. Now I was ready to get started evaluating the system.

The NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier In Use

The M12 is a surprisingly flexible component. The user has a wide range of control functionality within the intuitive menu system. You can select inputs, rename inputs, make inputs active or inactive, set up and control the subwoofer(s) including trim functions and high and low pass filters. The unit has bass and treble controls, a balance control (nice) and fixed gain settings for use as a home theater pass-through. I could go on, but suffice it to say that NAD has packed this preamp with all the control functionality I could ever want.

So what kind of summary can I think of to describe the audible character of these components? Well I did a quick, informal word count on my listening notes and found a recurring theme in my listening impressions. The words that kept showing up were words like analog, liquid and emotive. Yep, the NAD products amazed me with an analog-like richness despite their digital architecture. This is not what I was expecting based on my past experience with Class D amplifiers. I was expecting an etched, forward, maybe even harsh sound. But that is not anything like what was heard.

Let’s start by discussing the sound of computer audio over the asynchronous USB interface. The albums I’ll write about immediately below were all 24/96 FLAC files that I downloaded from various internet sources. They were played over a Dell laptop on JRiver Media Center 20.

Leading off with Roberta Flack “Killing Me Softly”, I heard what was described as an eerie analog-like quality. I went on to say that the effect was actually jarring in its preeminence within the performance envelope.

This analog quality was further reinforced with Aretha Franklin’s “30 Greatest Hits” album. In this case, I pegged the sound as analog but I also went on to note the liquidity of the music. This was especially prominent on “Freedom” where Aretha’s voice was crystal clear and lifelike. Other songs on this album did not fare as well because the NAD combo was capable of revealing flaws in many of the older recordings I auditioned.

So I decided to try something on the modern end of the spectrum and cued up Beck’s award-winning “Morning Phase”. This Beck album proved to be a great test of the NAD’s excellent bass response. This album can tend toward being too warm, but over the NAD, the bass was a spectacular accompaniment to the music. It was full and deep to be sure but it was also very much in rhythm and in tune. I was very impressed by what I heard in the bass on this record.

My main impression of “Morning Phase” was of a smooth and low distortion sound that was free of any nasty artifacts that were endemic of the older recordings I had started off auditioning. This meant that the NAD gear was able to step aside and allow the music to shine in a way that held me spellbound throughout the entire album. This was indeed a high-end performance that I would challenge any other amplification product to try and match.

I did listen to more than a few LP’s over the NAD’s phono input. Yes, the stock M12 comes with a phono input that is fully adjustable for load and gain via the on-screen menus. My cartridge is a Sumiko Blackbird which is a high-output MC design that is designed to drive a typical MM load/gain setting.

I started with an original pressing of “Coltrane” on the Impulse! Label in Stereo. This particular album, produced by Bob Thiele and engineered by Rudy Van Gelder, has been pristinely preserved. This was the debut of the classic “Trane Quartet” and it signified his return to a more melodic style. I personally feel that Coltrane was THE jazz virtuoso on sax

The NAD brought out the emotion like never before. It was amazing!!! This too was not expected from a digital component. As I mentioned earlier, most of the Class D amplifiers I have heard have at least some amount of a “zzzzzt” sound that can be very annoying. Class D amps have also sounded rather grainy to me in the past. Well, I heard none of that kind of mess from the NAD M22. The performance was simply pure, clean and balanced.

The frequency balance was spot on as in “The Inch Worm” which had deep bass, sparkly cymbals and a clear midrange. This top to bottom balance was in many ways the NAD’s calling card and it meant that you would hear every note with the correct inflection and nuance. This is a big part of what the Coltrane sound was all about

The pace on “Miles’ Mode” was as blistering as I have ever heard. The NAD left nothing on the table with this song. This was as pure sounding as I’ve heard this album; dark backgrounds, with brilliantly clean leading edges and absolutely no overhang.

Later I gave a listen to Jackson Browne “Running on Empty”. Like “Coltrane” above, this was also an original pressing. Songs on this album were cobbled together and recorded in various live venues, hotel rooms and even one on the band’s bus. This was a band on tour for sure. This was one of my favorite albums in high school so that means it will be a lifelong favorite

Even I was taken by surprise when it came to the low levels of background noise on this record. It still sounded so true to the music that I fell in love with all those years ago. The variety of the musical styles, the instrumentation and venues were apparent on each individual song. Over the NAD duo it became something of a “Master Class” on how to reproduce music in the home.

Whenever I review real high end equipment, there are always times where I just let the music and the performances speak for themselves. This was one such instance and the NAD boxes spoke with an authoritative voice that had me riveted.

The M12 review unit that I had included the NAD BluOS module that allows one to play music over their home network (or directly over Bluetooth). It took me a few tries to get it to work because the original firmware had issues. Once I updated the firmware, then the Bluesound system connected quickly and worked quite well.

I have hundreds of albums on a NAS server. These files range from MP3, to FLAC, to WAV, to AIF, to ALAC, to DSD. The BluOS module could play them all. And it did it wirelessly. What I did was download and install the free app onto my HTC One phone. This app found all the music on the NAS and indexed it to a reasonable degree. If I owned the BluOS, then I would need to spend some time reacquainting many files with their cover art, for example. But for the purposes of this review, the system worked great just the way it started up.

The module and app conspire to replace iTunes or JRiver or whatever media player you are using. I found that the Bluesound app worked best in a playlist mode. So even short listening sessions started with me creating a playlist on the fly. I was constantly searching for the next track to add and once the queue was more than about 5 songs or so then I would marvel at the eclectic choices I had made! Hey, it was serious fun! But it wasn’t just easy and fun – the system could stream high resolution seamlessly which meant I got some incredible audio performance from this system.

But even material sourced from Redbook CD’s were a joy – take Emmylou Harris’ “Quarter Moon in a Ten Cent Town” which I ripped as a FLAC file from the CD by Rhino. On “To Daddy” (written by Dolly Parton), Emmylou’s plaintive voice floated between the speakers and really communicated the song’s bittersweet message while more upbeat songs like “Leaving Louisiana in the Broad Daylight” benefitted from the strong bass and broadly fleshed out analytical accuracy of the sound. Despite an analytical edge, the emotion in the music remained intact not having been squelched by the NAD’s modern design architecture.

Despite that it wasn’t one of Harris’ big hits; my personal favorite track on this album is “One Paper Kid”, a duet with Willie Nelson. Over the NAD combo, there was excellent separation of voices while the strings amazed me with their brilliant presence in the room. Paradoxically for an acoustic track, this song highlighted the dynamic capabilities of the NAD system which were beyond reproach.

I closed out my serious evaluation with Metallica “Load”. Why, you may ask? I say “why not”?!!!! The NAD combo would be a great choice for anybody who enjoys rock music – they have wide dynamic range (macro) and with “sleeper” microdynamics. (They aren’t in your face but over extended listening you find that the NAD setup has a great deal of headroom). Plus once in a while you just have to crank it.

This whole album is a lot like the fat lady singing. I am totally sold on this set up now and a big part of that is “Bleeding Me”. This song tests every aspect of the system. The NAD stared down Satan and did not flinch! Bass, treble, mids, oh my! Dynamics? Check. Are you not entertained? I am!

The NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier On the Bench

All below tests were run with one channel driven. On the M12 preamp, the signal was fed through the left channel balanced input to the balanced pre amp output. On the M22, I used the left balanced input through to the left speaker output.

The first test I ran on the M12 was a 1 kHz sine wave at 2V RMS. THD+N measured just 0.00131%. Check out the very different and orderly harmonics. This harmonic structure is indicative of a unique design.

This is the Intermodulation Distortion Test with signals at 60 Hz and 7 kHz. The M12’s measured IMD at 6 dBV (2 Volts) came to just 0.0023%.

This is the other IMD Test we run with signals at 19 kHz and 20 kHz. The B-A peak is the difference between the test signal and the level of the 1 kHz tone generated in sympathy to the two test tones. I measured this on-screen and got a B-A peak response of -123.5 dB at 2 Volts output!

This plot shows the frequency response of the NAD M12 at 2 Volts output. I had the M12’s ADC set to 192 kHz for this test. The plot is nearly flat to 20 kHz where it begins a slow drop to – 5dB at around 85 kHz at which point the amp’s filters kick in.

I wanted to show how the filters worked when the M12’s ADC was set to 48 kHz. Notice the sudden roll off starting at 24 kHz just as one would expect.

The M22 tested at 10V and 8 ohms (12.5 watts) presents a very clean distortion profile. The calculated THD+N is just 0.00113%.

Increasing the output to 40V into 8 ohms (200 watts), the THD+N remained well below the threshold of audibility at just 0.00302%.

Check out the response at 40V into 4 ohms (400 watts). The distortion + noise was still under 0.01%! The resistors were dissipating a lot of heat during this test.

The M22 IMD test at 19/20 kHz and 2V shows a B-A peak of around -90dB.

Here is the M22’s frequency response into 8 ohm at 2V. It was essentially flat from 2 Hz to 20 kHz.

Conclusions about the NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier

The NAD M12 and M22 amps impressed me more than any amplification component I have reviewed in the last several years. Due to the products’ digital DNA, I was prepared to hear a bright, grainy or thin sound. What I heard was in reality the very exact opposite of this.

The M12/M22 products offered a sound that was always liquid and emotive. The sound was reminiscent of good old Class A amplification in this regard. They thankfully differed from Class A in being able to deliver huge gobs of power with a lifelike microdynamic structure which impressed me more and more each time I listened to the amps. And the frequency balanced held up even when I pushed the amps.

The units also shone on the test bench with high power output, low distortion and a distortion profile that was unique among amplifiers I have tested. I believe this balanced harmonic structure had much to do with the smooth and non-fatiguing sound.

NAD has brought to market a pair of spectacular products with these amplification components. People take notice – NAD deserves full consideration as a contender in the high end. Please do yourself a favor and be sure you fully audition these fine products before you make a final purchase decision.

The post NAD Masters Series M12 Preamplifier and M22 Stereo Power Amplifier Review appeared first on HomeTheaterHifi.com.

The advantage of integrated amplifiers is the preamp and amplifier sections are built into one chassis, resulting in shorter signal paths. It takes less space and eliminates the need for another set of cables.

All Raven Audio integrates and amplifiers are self-biasing; you never have to adjust tubes for a perfect match.The chassis is manufactured of sturdy 14-gauge carbon steel with an aircraft-grade aluminum face plate. The handles are made of schedule-20 carbon steel with knobs machined from aircraft-grade aluminum.

So there I was, perusing some audiophile sites on Google when I came across this post from Raven Audio’s Dave Thomson. He was claiming that his new integrated would perform as well or better than similar products that sell for twice the price:

“If you do not think your chosen Raven Audio product is the absolute best amplifier or preamplifier you have ever heard in the price range AND up to double the price, we will refund your investment, no questions asked. We want every single Raven Audio customer to be 100% satisfied with their purchase.”

Usually, I hear this kind of boast from cable manufacturers and I don’t give them a second thought. Still, this was interesting, so I decided to take him up on the challenge because: 1) I had never heard of Raven Audio, 2) I like integrated tube amplifiers and 3) I love a challenge. I picked up the gauntlet, contacted Dave, and within a few weeks the Nighthawk “flew” in from Texas to my home in New England. Dave even sent me some extra tubes to try out to allow me to tailor the sound to my liking.

The Nighthawk MK2 comes in a silver colored baked enamel. With solid aluminum handles, a folded carbon steel chassis and solid aluminum remote, the overall solid feel of quality construction was undeniable. Self biasing tubes certainly make for easy set up (virtually plug-n-play), but what of the sound quality? And at 20wpc, can it really do some musical heavy lifting?

On the back, the speaker terminals allow you to optimize the speaker choices with 4 ohm and 8 ohm configurations as well as a sub out. No digital source inputs can be found on this device as there is no DAC on board.

When my unit arrived, I had to install the tubes which were carefully packed in bubble wrap and boxes. The instructions for installation were easy to follow and I had the tubes plugged in no time.

As a precaution, I used gloves when handling the tubes. Oil from your fingers could cause the tube to heat unevenly and crack the glass. Plus, if the tube broke while it was being pressed into place, the finger you save could be your own.

People ask me about “self biasing” and what purpose it serves. I can try to explain it in laymen’s terms as such:

The best way to understand bias is to think of it like the idle setting on a car. The fuel and air mixture is adjusted so that the motor runs smoothly; too much of either and the motor won’t run very well or even possibly not at all. The idea is to find the perfect balance for optimum performance. When it comes to tube amps the idea is similar, however, instead of fuel and air we are dealing with electrical current.

The purpose of setting the bias of an amp is to find the optimum setting for the flow of current when the amp is idling.

Too much and the life of a tube is significantly decreased and in extreme cases failure can occur; this is also referred to as “biased hot.” Too little and unpleasant distortion (crossover distortion) is produced; this is referred to as “biased cold.” The correct setting is crucial for an amp to perform at its best both functionally and sound wise.

Obviously, if there is an optimum setting, why not just set the bias to that point and leave it? Well, it’s not really that simple. It’s more like a moving target and not an exact setting. Think of it as an acceptable range, not one single point. The reason for this is that each set of tubes is going to have different performance characteristics that will affect how the bias should be set.

Even within a single brand of tubes you will find one set that may vary wildly from the next in terms of its operating characteristics. Unfortunately, that is one of the realities of vacuum tube production. For this reason, when changing power tubes in a tube amp it may be necessary to set the bias on the amp to make sure it is optimized for the new set of tubes and not the set you just replaced. Without getting too technical, basically through a series of design characteristics – mainly a resistor – these amps balance themselves against the current draw of a given set of power tubes. For this reason, they will normally function pretty well with a wide range of tubes without needing any adjustment. It’s just “plug -n- play,” however; I would still recommend buying a matched set of tubes for optimum performance. (Replacement tubes can be purchased from Raven Audio and many NOS tubes can be purchased off of the internet, though caveat emptor).

Of course, all of this is academic if in the end the Nighthawk doesn’t sing like a Nightingale. Terms that usually describe tube sound range from “warm and mellow” to “less harsh” than pure digital sound. They introduce second harmonics distortions that most people find euphonic. Tubes generally have a soft treble roll off that reduces the edginess in some recordings.

I’ll try to describe specifics in my music review section. In my set up, I ran my Oppo 103 analog outs into the Nighthawk. My interconnects were Kimber Cable PBJ’s, 1 meter lengths.

I played a variety of music through my Revel F12s and a pair of Legacy Audio Silhouettes that I had on hand for a review. Both of these speakers have moderately good efficiency (over 89). The higher a speaker’s efficiency, the less power you will need to drive them to louder volumes. Keep this in mind if you are contemplating a 20 watt tube amp. To go higher in SPL, get more efficient speakers or purchase a tube amp with more output (such as a Raven Audio Shadow MK2 50wpc stereo amp, for instance).

When powering up the Nighthawk, I noticed the sound quality of my music improved over time. The music sounded thin and the sound stage was flat. In time, I learned to let the unit warm up for at least 10 minutes before I would sit down for serious music listening. Solid state devices are usually ready to play music the second you turn them on.

With tubes you need to be a bit more patient. I often do my more serious listening at night in a very dark room. I find light, in general, too distracting for my listening habit. In the case of listening to the Nighthawk in a darkened environment, I had the added benefit of seeing the soft glow from the compliment of tubes…and I found that somewhat mesmerizing and soothing. Seriously. Glowing tubes look cool! I can just about guarantee that anyone that walks into the room during your music session is going to notice them and say something. As a tube owner, you should take pride in that it draws the eye.

Now on to the music. I have eclectic tastes and play everything from Bach to Flaming Lips. Most of my music is in a hi-rez format. Feeding the Nighthawk hi-rez is a great idea. (GIGO: garbage in, garbage out applies here). Now I don’t want my descriptions here to imply that tubes “loose” some sort of sound quality. They definitely affect the sound, but not in a bad way…unless you are some purist who demands the sound be exactly what the recording engineer captured (whatever that means).

On the Nighthawk, it lost its edginess and became quite listenable. The slight tape hiss that you could normally hear was diminished and the sound stage depth improved, making it sound less 2 dimensional. And this change in quality was not subtle. In fact, I found that most of my music that was mastered off of analog tapes (especially recordings from the 50-60’s) sounded smoother and less over sibilant. It wasn’t that they lost detail, but they sounded more natural and relaxed.

The soundstage was often improved and the sound became less tiring to listen to over long listening periods. This is what tube lovers like about these devices. Musically, they are just very natural sounding. Jazz music also sounded good. I listened to Dave Brubeck, Hiromi and Miles Davis…all of which sounded musically sweet on the Nighthawk.

THE RAVEN AUDIO NIGHTHAWK MK2 is a High Performance Amplifier.

After several weeks of auditioning the Nighthawk MK2, I can say that it is musical, natural sounding, easy to operate, and has a major “coolness factor” with its array of glowing tubes. With the right speakers, you will never feel you lack power and you just might pull out some music that you shelved because the recordings sounded harsh.

Raven Audio has quite a selection of preamps and amplifiers, and the Nighthawk MK2 is reasonable priced for the quality of construction and sound it offers. If you are interested in getting into tubes for the first time, the Nighthawk MK2 is a great choice. The fact that it is self biasing means you can “set it and forget it”. The Nighthawk MK2 will give your music wings!

The post Raven Audio Nighthawk MK2 Integrated Amplifier Review appeared first on HomeTheaterHifi.com.

It’s very well put together, generates plenty of power and features a high resolution DAC section. Its sound is quite luxurious as well which is the most important part of all.

The first word I think of when I hear the name Mark Levinson is “quality”. That’s because Mark Levinson feverishly pursues the highest quality in everything they do. It starts with the concepting of their products and carries all the way through to the retail end of their business model. So it is always a pleasure to get their products in for review. Not only does this mean I will get a high level of personal and professional attention, but it also means I will be reviewing a product that will bring great pleasure during the time I have it in my system.

Most of our readers are aware that Mark Levinson products exhibit massive build quality and impressive performance. That is their hall mark, if you will. In many cases, though, firms come out of the gate with great products and then stagnate over the years only to be forgotten by their consumer base. This is not the case with Mark Levinson. They are always striving to upgrade and improve their product line.

Enter their newest offering, the No585 integrated amp. This amp is a reflection of proven amplifier technology given a fresh spin by their engineers. It most keeps pace with the changing world mostly through the inclusion of a high resolution DAC section that represents some cutting edge thinking. Take two short minutes to enjoy this promotional video on the No585 and then read my detailed review below.

Mark Levinson has been improving, updating and refining designs of their amplification components in recent years. The epicenter for their design advancements is Harman’s new Shelton, Connecticut facility. This facility and the people who work there comprise what Harman Luxury Products Group refers to as their “Engineering Center of Excellence”. The No585 integrated amp is a major realization of the development work taking place in this world-class R&D facility.

I want to start by discussing some of the broader design elements of this amplifier before giving an overview of the technology inherent to the No585. The first thing one notices about the No585 is its sheer size. It is over 7-1/2” inches tall (with feet), nearly 20” deep and weighs 72 pounds in the raw. This is one very large integrated amplifier. Not surprisingly, it has a high power rating – 200 Watts per channel into 8 ohms!

The No585 has a built-in DAC that can process LPCM signals up to 32-bit, 192kHz or DSD up to 5.6 MHz. All types of digital inputs are supported here, including asynchronous USB. This DAC uses the latest ESS Sabre DAC chip with a proprietary current-to-voltage output stage which I will discuss in a bit more detail below.

This amp has line level outs in case you want to bypass the internal amps and use it as a DAC or pre. It does not have a phono stage. The No585 does have a subwoofer output with selectable 80Hz high-pass filter for integration with a subwoofer. Speaker binding posts are the famous Mark Levinson “hurricane” posts. The amplifier has extensive DC trigger controls as well as Ethernet and RS232 connections for set up, monitoring and control of the unit.

I have read over the technical information provided by Harman. Some of the most salient design objectives were to provide “a deep, expansive soundstage; accurate image placement; extended low bass response with good pitch definition; and detailed high frequencies free from ‘etching’.” How would this be achieved? The answer can be summarized through a thematic discourse. The design ‘themes’ that take the No585 in the stated direction are:

• Cascode Architecture
• Differential Design
• All-Discrete Analog Circuitry Throughout
• Multiple Power Supplies
• High Quality Components

Cascoded amplifiers have been around for decades and they can be used for a variety of benefits; the one cited by Harman is that they are used in the No585 to enhance the linearity of the amplifying transistors. Specifically, Harman is using a folded cascode which employs three individual transistors that operate as a single transistor with greatly improved characteristics including an output voltage range that extends almost all the way from rail to rail.

These cascoded transistors are connected as differential pairs in order to reject common-mode signals. The outputs of these folded cascodes are then fed to a current mirror circuit which mirrors and adds currents from both halves, thereby canceling out a vast majority of the nonlinear components in the signal. The gain stages then feed a Darlington output stage which uses several emitter-followers that isolate the output of the folded cascode from the load being driven.

Positive benefits of the design and execution of the No585 gain stages is that they provide accurate, low noise, low distortion and wide bandwidth amplification. And there is very little global negative feedback – less than 20dB to be exact.

The No585 uses an R-2R resistor ladder network for the volume control. This is widely regarded as the best volume control topology out there. Of course, Harman has made improvements to lower the resistance of this circuit and by using special analog switches with very low voltages in routing the currents through the circuit.

In reading over the technical information provided, I was able to count no less than 10 individual power supplies in the No585. At the heart of these power supplies is a massive 900 VA toroidal transformer. Separate windings mean that this amplifier operates as a true dual-mono amplifier.

The No585 uses tantalum nitride thin-film resistors and small-value polypropylene foil capacitors in critical locations within the architecture. There are no coupling capacitors in the signal path.

On the digital audio side, the No 585 uses a Cirrus Logic receiver chip and the latest ESS Sabre DAC. They also employ an Analog Devices SHARC DSP chip to implement the Clari-fi algorithm.

The No585 offers a wide range of adjustments that are unique. One of these is that they allow user selection of three digital filter options – fast, slow and “minimum phase”. This gives the listener even greater control of the sound he/she is hearing.

Setting up the No585 was generally very straight forward. I placed it in my rack, connected my source components to the most appropriate (i.e., “best”) input, connected my speakers and plugged in the No585’s mains power cord. That was all it took to get the unit connected and ready for music making.

Not so fast, though, as this is a modern digital component with a flexible interface that needed some attention to optimize the whole affair. You are thankfully guided through the set up and menu system by a very well-written 16-page owners’ manual.

The first thing I did after plugging everything together was to go through and rename the inputs to match the connected components. Many common names are pre-installed and these can be readily selected. If they are not there, then you can key in a unique name (like “Blu-ray 2” or “Oppo”, etc.). You can also hide unused inputs for convenience and to cut down on potential future domestic disputes.

The menus allow selection of the PCM Filter – slow, fast or MPhase (minimum phase). These settings affect the presence of some very minor ringing or pre-ringing and are there for you to tailor the sound to your personal tastes.

If running compressed audio, then you can also turn on Mark Levinson’s Clari-Fi circuitry. This is an advanced DSP algorithm that is said to recover clarity and detail lost in the process of compressing audio files. Clari-Fi is also available via direct input from the included remote control. This level of direct control is a nice touch.

There are a number of other settings for power saving, display, volume control, etc. There is also a HT bypass setting if you want to use the No585 to drive the main speakers in a surround system. All in all, this is a very flexible product.

Probably the biggest hurdle for me was that I needed to download and install USB drivers so my Windows computer could send high resolution audio to the No585 via the asynchronous USB interface. The drivers are easy to find on the Mark Levinson web page and worked like a charm. So this was not much of a hurdle in actual practice.

So I just finished watching some promotional videos related to the No585 that are on the Mark Levinson web site. One of the quotes on there is that Mark Levinson is building products with an “heirloom feel”. I love that quote and I agree wholeheartedly! There is something very satisfying and reassuring about the build quality of the No585. There is luxury in everything they’ve done here – the look of the product, the clean machined lines of the faceplate, the weight of the volume knob, the weight of the unit itself, the look of the red LED display, even in the authoritative click of the internal relays. What better way to inspire confidence in a product than through this high level of quality workmanship?

I know that is all well and fine but what did this amplifier actually sound like? Let’s dive right into the answer:

The first song on the album is “Walking in Memphis” and right out of the gate, the No585 impressed me with a big and powerful sound. I felt the amp had a rock steady grip on the speakers which led to an incredibly realistic frequency balance from the lowest lows to the highest highs.

I love the way the piano is captured on the Marc Cohn album and the No585 let it shine, especially allowing the instrument’s percussive qualities through. The Levinson also handled Cohn’s voice brilliantly and I enjoyed the holographic sound of a man sitting at a piano in this very room signing “Silver Thunderbird” (which is one of my all-time favorite songs, BTW).

When it comes to the heart of the music, the mid range that is, the No585 was no slouch in this department either. This was heard through Margo Timmins’ voice, her delicate voice floating above the speakers in an eerie display of aural realism. But more impressively there is the duet with her and John Prine, “If You Were the Woman and I Was the Man”.

The No585 tracked each singer’s vocals very closely making a massive statement about the transparency of the circuit design. I was most impressed by the unit’s ability to not only divide but also to combine their voices at the same time.

So it didn’t matter whether I was listening to LP, CD, compressed audio or high-resolution audio because no matter what I listened to, the No585 had me enraptured and transfixed by what was going on audio-wise. This is one product that was mesmerizing to listen to at all times. It just made everything sound its best!

THE MARK LEVINSON NO585 is the best sounding integrated amplifier we have tested.

Let me go ahead and state that the No585 is the best sounding integrated amplifier I have ever had in my system and quite possibly the best I have ever heard anywhere at anytime.

Let me go ahead and state that the No585 is the best sounding integrated amplifier I have ever had in my system and quite possibly the best I have ever heard anywhere at anytime. I could not hear a single audible weaknesses in the performance. In fact, if I were pressed to choose just one word to describe the No585, I would choose “mesmerizing”. That word showed up in my listening notes many times.

Along with this great sound you also get a very nice box – heavy, tightly machined, luxurious and with the iconic Mark Levinson look – two-tone faceplate, red LED readout and the hurricane binding posts. This product can easily serve as a centerpiece to a true high end system, bringing pleasure for years to come.

The post Mark Levinson No585 Integrated Amplifier Review appeared first on HomeTheaterHifi.com.

That’s a load of features. In addition, it sounds exceptional. The massive RB-1590 power amplifier can deliver 350 WPC into an 8 ohm load, but still has plenty of ability to reveal fine detail and subtle tonal character. Together, they delivered one of the best soundstages I’ve heard in my room with my Gallo Reference 3.5 loudspeakers.

Rotel is a company well known to audio enthusiasts that’s been around for a long time. Since the 1960’s in fact. They were one of the first (if not the first) high end audio company to use the model of designing their own components, but having them manufactured overseas. This has always positioned them as a value leader.

Rotel’s new preamp and power amp combo, the RB-1590 and RC-1590, offer up very impressive specifications for a modest asking price. In particular, the RC-1590 preamp is loaded with features most every sub-$2000 preamp could only dream of. The RB-1590 amplifier offers 350WPC of class AB power for $3000. But, as we all know, features and specifications are worth only the paper they’re printed on.

What matters is how the components perform in the listening room. After spending some time with the RB and RC 1590, I was very impressed. I tested these components as a matched pair, so this review will be about their sound together. I did not get a chance to test each one separately.

We’ll start with the RC-1590 preamplifier. This is certainly not what you’d call a “purist” preamp. It has pretty much every feature you could think of, some of which you’d expect to find in a home theater surround sound processor, not an audiophile preamp. The core of the RC-1590’s design rests on two completely separate power supplies for the digital and analog parts of the unit. The analog side offers both balanced and single ended inputs and outputs.

There are three single ended and one balanced analog input plus a moving magnet phono input, along with two single ended and balanced preamp outputs. In addition, the RC-1590 has a single ended line output and two single ended mono subwoofer outputs. This is a fine complement of inputs and outputs for a preamp but it doesn’t end there. In addition to analog preamp functions, the RC-1590 has an internal DAC based on an AKM 32 bit 768 kHz chip, although inputs are limited to 24 bit, 192 kHz.

There are three coaxial and three toslink optical inputs as well as two USB audio inputs that operate up to 192 kHz, 24 bit. A rear panel USB-B connector is designed for most all USB audio devices, while the front panel USB-A connector is designed to work Apple iOS devices. The rear panel USB also accepts both DSD and DOP audio in 1x and 2x modes. There’s even an integrated Bluetooth dongle that allows you to stream audio to the RC-1590 over Bluetooth using either traditional Bluetooth audio or APTX streaming.

There are bypassable tone controls and balance control. Any input can also be set to fixed gain, disabling the volume knob for that input. This allows any input to be set up as a home theater pass-through for use with a separate surround sound processor or with any other volume controlled source such as Sonos®.

Since this is how my system is set up, this was a particularly nice feature to have. An Ethernet jack on the back allows the unit to be connected to the network for firmware updates and automation system integration, but no audio files can be streamed over this connection.

The build quality and feel of the preamp was quite nice for the price. The case itself was the typical stamped steel you’d normally find on a piece of consumer audio equipment, but the front panel and quality of the controls was very nice.

The RB-1590 amplifier is significantly simpler than the preamp. The cosmetic design is similar, but the RB-1590 is a very heavy and solidly built amplifier. The amp will deliver 350 WPC into an 8 ohm load with both channels driven. That’s quite a lot of power for a stereo amplifier. It operates in class AB mode, as you’d expect for this sort of power rating.

The amp is not completely dual mono inside, but close. There are separate toroidal transformers for each channel, but each side of the amp does share some power supply components. There are both single ended and balanced inputs available, dual 5-way binding post outputs that are very solid, and 12V trigger inputs and outputs for remote turn on. While the amp does have balanced inputs, it is not a fully balanced design end to end (this is also true of the RC-1590 preamp).

I set up the Rotel pair in my system together and allowed them to break in on casual TV watching duty for a while before testing. I did not test the components separately, only as a pair. Most of the time the preamp was fed with my Oppo BDP-105 player used as a USB DAC with Pure Music audio player software. I did try out the internal DAC, but most of my listening was done using the RC-1590 as a traditional preamp.

The first main impression I got when listening to the Rotel pair was that of space. The soundstage on most every album I played was significantly wider, taller and deeper than with my normal components (an Emotiva RSP-1 preamp and a NewClear NC-1000L amplifier). From combo jazz to electronica, the soundstage reached a good yard left and right from my Gallo Reference 3.5s, with soundstage height up towards the ceiling. The depth was certainly recording dependent but on good recordings like Jon Faddis’ Remembrances in 24 bit 96 kHz, the soundstage seemed to go well past the back wall of the listening room. This is a hard thing for an audio system to do. A lot needs to go right for all those spatial cues to make it through to your brain, so components that can do it tend to have many other redeeming qualities.

The Rotel pair did an exceptional job of extracting detail out of recordings, without being too harsh and revealing of faults. Both micro and macrodynamics were excellent. The big power of the RB-1590 had no problem controlling the bottom end of the Gallo Reference 3.5s in a way very similar to the 500WPC NewClear NC1000L I typically use. The bass performance gave up nothing compared to my normal equipment, but didn’t seem to be any better than my usual system.

Microdynamics I think were improved a bit. Some recordings I remember sounding a bit flat and lifeless were more engaging and enjoyable. I usually associate the “aliveness” of a recording with microdynamics. Those small, subtle changes in loudness are one of the main things that make a recording sound exciting and alive as opposed to flat and boring for me. As with my normal system, the timbre of the Rotel pair was quite neutral. No tube like warmth present, but no glare or harshness either.

When I listened to the built in DAC, I was hard pressed to hear any real difference between the Oppo BDP-105 (which uses a well-regarded Sabre 32 bit differential DAC chipset). This is actually pretty high praise, as the BDP-105 is one of the best USB DACs I’ve heard priced around $1000. I think the bottom line is that the built in DAC of the RC-1590 is very good, and you’ll have to spend considerably more than $1000 to do significantly better. This makes the RC-1590 an even better bargain. You get a preamp with excellent sound quality loaded with features, and very good DAC for $1750. I can’t think of any other preamp or preamp+DAC combo that can offer the same for even close to that price.

Measurements were performed with a M-Audio Profire 610 Firewire sound interface and Spectra Plus FFT analysis software. I drove the RC-1590 using an analog input, so the results you see here do not include any effect of the built in DAC. The RB-1590 was measured using an 8 ohm power resistor as the load. The signal level used to drive the amp resulted in an output power of about 40W into the 8 ohm load. This was necessary to keep the voltage across the power resistor within the range of the Profire 610’s inputs. If I tried to run the amp at any significantly higher power, the input of the sound interface overloaded. Still, this is a reasonable test of the amplifier performance since the average power output when playing music (even pretty loud) is only a few watts.

Once again, we’ll start with the RC-1590 preamp. I measured total harmonic distortion plus noise at 60 Hz, 1 kHz and 10 kHz. Distortion levels are quite low, near that of the sound interface itself at around 0.01% for each tone. The dominant harmonic is the 3rd harmonic, with odd order harmonics decreasing at higher frequencies, although power exists out to very high harmonic order.

Intermodulation distortion, measured with 60 Hz + 6 kHz tones was a very low 0.0085%.

THD+N as a function of frequency shows measurements that make sense with the spot checks above. The level is just below 0.01% from 20 Hz past 20 kHz before it starts to rise (an effect of the sound interface, not the preamp).

Frequency response is flat as a board as expected all the way to the limit of the sound interface.

I performed the same suite of tests with the RB-1590 amplifier, but with the amp driving an 8 ohm power resistor. The sound interface was wired in parallel with the power resistor using clip leads.

THD+N was only slightly higher at 40 W power delivery than the preamp, which is a very good result. Odd harmonics once again dominated as expected from a push-pull amp, but even harmonics were not completely absent like they were in the preamp. The THD+N versus frequency plot shows slightly higher numbers than the spot check but still a very low 0.03% from 20 Hz to over 20 kHz.

Intermodulation distortion was even lower than the preamp at 0.006%.

Again, frequency response was ruler flat to the limit of the sound interface.

In all cases, the measured performance of the Rotel gear was without fault. Most all the measurements you see here are actually measurements of my tools, not of the Rotel equipment.

For the money, you’d be hard pressed to find a better sounding, more fully featured preamp and power amp combo than the Rotel RB-1590 and RC-1590. The preamp in particular is loaded with useful and uncommon features that make it as versatile as they come. The RB-1590 power amp has lots of power capable of controlling virtually any loudspeaker, while still being able to deliver a subtle, detailed presentation. The soundstaging performance of the pair was excellent, amongst the best I’ve heard in my room with my loudspeakers. I would not hesitate to recommend this combo for anyone looking to spend about $5000 on a complete set of stereo audio electronics.

THE ROTEL RB-1590 AND RC-1590 AMPLIFIER AND PREAMPLIFIER sound fantastic, and are excellent values for their price point.

The post Rotel RC1590 Preamplifier and RB1590 Power Amplifier Review appeared first on HomeTheaterHifi.com.

If cool, quiet operation in an amplifier is important to you, the SDA-2400 deserves your attention.

Have you noticed lately that Class D amplifiers are on the rise in the audiophile world? A common misconception about them is that the “D” stands for Digital. It does not. These are switching amps that use a modulator (usually a MOSFET) to convert the input signal (analog or digital) to a PWM (Pulse Width Modulated) signal. It wasn’t too long ago that many Class D amps suffered from increased THD, dead time and shoot through, but most of those issues have now been overcome.

These new switching amps can rival the best Class A/B amps for shear power and beat them handily in efficiencies that exceed 90%. Lyngdorf has designed the SDA 2400 to be a highly dynamic switching amplifier with extremely low and linear distortion in the full frequency audio range. Boasting 200 watts into 8 Ohms, I think they have succeeded in their design goals.

Based out of Denmark with a USA office in LA, Lyngdorf has been known for audio components that are recognized worldwide as some of the best high-performance digital audio products available. Their R&D has developed Intersample Clipping Correction to restore clipped signals back to their original shape and a digital room correction that is built into their TDAI-2170.

The output stage of a switching amp is either fed a digitally modulated signal of PCM-to-PWM, or an analog-to-PWM. The SDA- 2400 is of the later analog type. The modulator converts the analog input signal to a PWM carrier that operates at an extremely high frequency. The magnitude of each PWM is described as width, as opposed to height, as in a PCM signal. The incoming signal is up-sampled to a PWM signal, which in the case of the SDA-2400 is 390 kHz.

Finally, the signal is fed to the H bridge output stage where the fixed 390 kHz frequency passes through a 12dB low pass filter at 50 kHz, which gets rid of phase problems in the audible range (effectively, any frequency above 44.1 kHz).The output filter coils used by Lyngdorf are ferrite cores which give the signal both low distortion and excellent linearity. The switching speeds are controlled by the latest technologies in MOSFET designs. (I will not bore you with a MOSFET design lecture. GOOGLE it).

This excellent switching performance increases the overall efficiency of the amplifier and greatly reduces the heat production that Class A/B amplifiers suffer from. Class D amps are often <90% efficient. The energy does not get converted to heat. Generally, Class A/B amps are around 50-60% efficient. Class A is around 30%, which is why you can fry an egg on them after an hour of music listening.

Thus, you will notice that the SDA-2400 does not have any ventilation holes on the top, bottom or sides. This sealed design also helps keep dust out of the component. After many hours of use, the SDA-2400 never even became warm to the touch and we know that heat is the mortal enemy of electronic gear. Even when idling, the “On/Off” nature of the MOSFET is optimized to keep distortion to a minimum.

Nothing is perfect, though. The biggest cause of MOSFET distortion is the switching timing, the On/Off speed, or more precisely the time the circuit is instructed to turn On vs. when it finally does turn On. Lyngdorf selected drivers that have as low as a 20ns delay and these are matched within 1ns between On/Off. If a switch stays On during a Off cycle, you have shoot through, which will eventually destroy the circuit.

If it doesn’t turn On/Off precisely, you can get distortion and timing errors. The SDA-2400 uses much less feedback on the circuit as other Class D amplifiers might. The use of negative feedback helps reduce the amount of distortion from less than ideal components. Ultimately, the noise floor is very low and linear in the audible range. Placing my ear up to my speakers with the music paused revealed absolute silence without hiss from my tweeters. Silence is indeed, golden!

Finding room for a new component is sometimes tricky in my listening room, but because the SDA-2400 was relatively thin and light, I decided to set it directly on top of my Emotiva UPA-100 mono blocks. As you can see in the picture.

The SDA-2400 can accept Toslink, digital coaxial, RCA analog connectors as well as a balanced analog input. There is a selector on the back panel that permits the selection of one of those choices. You can leave the amp in standby with the option of an audio input signal “waking” the amp up, having a 3.5 mm trigger or leaving the amp On all of the time. There is no On/Off switch on the front panel, but there is one on the back panel.

In standby mode, a small white LED blinks slowly (like my Mac Mini, actually). When the amp is On, the LED stays solidly lit. My pre/pro does not have a digital out, so to test the amps digital input I used my Oppo 103 to connect to it via a coaxial connector. If you do this, your digital device must have a volume control. Make sure the volume is low or off when you first power everything up and work your volume up till you get to comfortable sound level. I learned the hard way… so you don’t have to. I ultimately settled for the analog inputs via my pre/pro. It offered me room correction, DSP and bass management prior to amplification, but at least you have some options. I used the audio signal input to turn the amp on. I noticed over time that the amp did not always spring into action when I started with soft music. It took the relay a few seconds to detect a signal and the actual turning on process took another 2 seconds, sometimes clipping the beginning of my music selection. My other option was to leave the amp on all of the time, which I do not like to do. The amp will automatically go into standby mode after about 20 minutes of no audio input signal. As long as your speaker cables are wired in-phase, you are ready to go. For the record, my interconnects are Kimber PBJs and speaker cables are Zu Audio Julians. My main speakers for this review are Revel F12s.

I have heard from some critics that switching amps have to use harsh filters to remove the PWM carrier and that this makes them sound un-natural and un-musical. Lack of linear output is another complaint, which can be true in other designs. Others argue that the bass is flabby (ironic, since many powered subs use a switching amp). Fortunately, that was not what I found with the SDA-2400. I ran music through it that would have revealed any issues with noise or distortion. I was especially curious to find what would happen to the delicate decay of an acoustic instrument.

It was stone quiet in the silent places. This was made all the more startling when inky silence was followed up with the full orchestra in the next movement. Solid bass from the brass and timpani were all there. The tinkling triangle could easily be heard above the fracas. Imaging was very good as well as depth of the sound stage. I was impressed with how big and solid the sound was.

Orchestral music is one thing, but the human voice is another instrument altogether. Dawn Upshaw’s soprano was beautifully rendered with the SDA-2400. Hampson’s baritone was natural and resonant as it should be.

Squire’s bass line was deep and taut as it leapt across Southside of the Sky, Anderson’s distinctive tenor rang out clearly above the band while Rick Wakeman glided through all of the glorious chaos with his keyboard. Percussions sounded impactful and the Wilson mix had it placed perfectly in space, being much more up front than the recessed 2002 mix. I know, how does a guy that listens to mostly classical music enjoy Yes? I find their music to be quite “classical”, I guess. Wakeman is a classically trained keyboardist. Listen to Cans and Brahms, or Howe’s acoustic guitar in Mood for a Day. Good musicianship is good musicianship. But I digress. Bottom line, the Lyngdorf can rock and roll.

The bass notes are full and resonant, the treble sparkles and the hammers softly hitting the strings are almost palpable. The SDA-2400 reproduced the piano sound pitch perfectly. All of the detail I was expecting was there. More importantly, the sound was natural and the final decay of the fading strings was not harsh or granular. A true test of the quality of an amp is not only how loudly it plays, but often how well it sounds when being delicate, just at the threshold of hearing. The SDA-2400’s sound was musically satisfying. The inky dark background was just perfect for music rendition. I can’t imagine a music lover not liking the sound of the Lyngdorf SDA-2400. In my few months of auditioning this amp, I never felt I was missing anything in sound quality. It kept its composure no matter what music I played through it.

THE LYNGDORF SDA-2400 is one of the Quietest Amps I Have Ever Reviewed.

The Lyngdorf SDA-2400 answered many of the questions I had about Class D amplification. Would I replace my current mono blocks with this amp? I am inclined to think that I might. It has the same amount of dynamic power as my monos, the sound quality is superb and the low noise floor is remarkable. Stereo separation is also excellent with a wide and deep sound stage. On the other hand, I got my monos for a bargain basement price. If I were starting out again with a nice 2 channel setup, I would certainly give the SDA-2400 a close look and listen. It is efficient, musical, runs cool as a cucumber and has plenty of dynamic power on tap. It took me a whole 5 minutes to setup and has a sleek low profile design that exudes quality. Whatever your personal opinion about switching amplifiers has been in the past, get ready for the future. Class D has finally evolved into an audiophile product with the Lyngdorf SDA-2400. With more manufacturers using Class D amplification these days, it might be time to for you to consider switching. The Lyngdorf SDA-2400 will change the way you think about Class D amplification

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Mark Levinson N^o52 Stereo Preamplifier Review Highlights

Mark Levinson, one of the most respected names in audio, has just released their latest stereo preamplifier design, the N^o52. Its looks, handling, and performance are what you would expect from Levinson: Extraordinary.

The N^o52 is in two chassis, one for the control section and one for the analog audio circuitry.

It has enough coax and XLR inputs to take care of anyone’s audio system, and even includes a phono preamp that has as many options for resistive and capacitive loading as do dedicated outboard phono preamplifiers.

The frequency response is flat out to 200 kHz. This is extremely difficult to design, and such a wideband response totally prevents any phase shift in the audible band.

The Mark Levinson N^o52 is simply an awesome engineering achievement. The sound is absolutely neutral, which is a hallmark of Levinson products. Distortion is as low as can be achieved with technology that is available to today’s electrical engineers.

Mark Levinson N^o52 Stereo Preamplifier Review Highlights Summary

• Easy to Navigate Inputs
• Extremely neutral sound
• Very low distortion
• Worth the price

Introduction to the Mark Levinson N^o52 Stereo Preamplifier Review

I have tested many Mark Levinson audio products over the years, and the performance always astounded me. Neutral sound and low distortion are the two phrases that audiophiles, including myself, identify with Levinson.

The N^o52 is Levinson’s latest, and greatest, preamplifier. They say it’s the best preamplifier they have ever designed. I believe it, and if you audition this product, you will too.

The Design of the Mark Levinson N^o52 Stereo Preamplifier

Although based on a switching power supply, the Mark Levinson N^o52 preamplifier still weighs 60 pounds.

There are two chassis that sit one on top of the other. The top one contains the control section, and the bottom one contains the analog audio circuitry.

Following is some information I received from Levinson’s engineers:

The N^o52 uses both switching and linear power supplies, and the linear supplies still contribute significant weight.  The casework and extensive internal shielding comprise most of the weight of the unit.

As in several other Mark Levinson products, the N^o52 actually re-generates AC power before the final rectification, filtering, and regulation stages.  It is this additional stage in the power supply that is unique to these products, as it goes well beyond the basic filtering and isolation functions that most line conditioners (even the really expensive ones) perform.

The functions and signal flow in the N^o52 power supply are as follows:

1.    Separate left and right switching power supplies generate +/-15V DC from the incoming AC mains.  These are fully encapsulated supplies, so they are mechanically and electrically very quiet.  The power supplies operate at a frequency of 70 kHz.
2.    These +/-15V rails supply power to separate left and right class D amplifiers, which use the same proven technology as the very well regarded Crown professional amplifiers.  These amplifiers are driven by precision oscillators to produce exceptionally clean, pure, 200 Hz sine waves.
3.    These clean 200 Hz sine waves function as the new, re-generated AC waveforms, which drive separate left and right custom toroidal transformers.
4.    The transformers each have three secondary windings, all of which are rectified and filtered to produce separate +/-22V and +8V supplies for each channel.
5.    Each of these power supplies feeds its own linear voltage regulator.  The regulators in turn provide stable +/-18V and +5V supplies for each channel.
6.    Finally, one last set of linear regulators provides ultra stable, low noise +/-15V supplies for the left and right channels for critical analog circuitry.  These regulators are located inside the audio chassis, close to the circuits they will be powering.
7.    Note that completely separate switching power supplies—none of which are connected to anything mentioned above—are used to power the digital control circuits in the N^o52.

The power supplies do not have—but also do not require—extraordinary amounts of filter capacitance.  Switching supplies, because they typically operate at frequencies several orders of magnitude above the 50-60Hz of a simple, conventional, transformer-based linear supply, are able to do their job with considerably smaller capacitors.  Also, the stability of the 200 Hz waveforms supplied by the class D amps, as well as the multiple cascaded linear regulators, contribute to making these supplies less dependent on large capacitors.

The preamp has three main gain stages, which operate in Class A, as they are based on high quality audio op-amps, which operate at enhanced bias currents.

1.    The input stage uses four low noise, high current op amps connected in a fully balanced instrumentation configuration.  This topology gets its name from its frequent use in the most demanding measurement applications.  It is known for its outstanding ability to reject noise and for the ease with which its gain can be changed to suit the incoming signal level.
2.    The volume control is realized with fully balanced, discrete, 16 bit, precision R-2R ladder networks.  These networks drive signal currents into the low-impedance inputs of current-to-voltage converter stages, also built from low noise, high current op-amps.
3.    Finally, the balanced outputs of the volume controls/current-to-voltage converters drive two complete, independent, fully balanced output stages, one for each of the N^o52’s main outputs.  These too are built from low noise, high current op amps and ultra precision resistors.

Note that all the stages are direct coupled (i.e., no capacitors in the signal path), with DC servos to actively adjust and remove any unwanted DC in the signal path.

The auxiliary outputs (also known as the record/play loop outputs) have their own completely separate signal switching relays and gain stages.  They are based on the topologies described above, only without any volume control.

The front panel of the N^o52 has the input selector on the left hand side, then the readout panel with buttons underneath for Aux, Setup, Enter, Display Intensity, Balance, and Mute.

The Volume Control is on the right, with a Standby button underneath.

A photo of the rear panel is shown below.

The top chassis (control circuitry) connects to the bottom chassis (analog circuitry) with an umbilical cord. The sockets are in the center of the two chassis, labeled “No 52 Control”. There are two additional umbilical cord sockets on the left and right sides of both chassis for DC power connections.  There are also USB, Ethernet, and Trigger connections on the top chassis. They allow the installation of firmware updates.

The bottom chassis has the connections for the dual mono configuration. The sockets are arranged in a mirror image. The top row has input sockets 1-7, with the first three being XLR balanced and the next four being RCA unbalanced. The bottom row has two sets of main outputs, both XLR and RCA, and one set of auxiliary outputs, both XLR and RCA. The Auxiliary jacks can be configured for SSP pass-through, or as fixed or variable volume outputs from a second input (to feed power amplifiers in another room).

The phono inputs are near the midline, and are RCA. The resistive and capacitive loading of your phono cartridge is set up using the menu. It has a very extensive list of values, much like a high end outboard phono preamplifier. Resistive loading includes 3.3 Ohms, 5.0 Ohms, 7.7 Ohms, 10 Ohms, 33 Ohms, 50 Ohms, 77 Ohms, 100 Ohms, 330 Ohms, and 47 kOhms. Capacitive loading includes 0.01 µF, 50 pF, 100 pF, 150 pF, 200 pF, 250 pF, 300 pF, 350 pF, and None.

The remote control is shaped very nicely to fit perfectly in the palm of your hand and has just the right number of buttons to use.

The Mark Levinson N^o52 Stereo Preamplifier In Use

I tested the Levinson preamplifier with an OPPO BDP-105 universal player, Emotiva XPR-1 monoblock power amplifiers, Classé CA-M600 monoblock power amplifiers, BAT-VK-75SE stereo tube amplifier, and Pass Labs Xs-300 monoblock power amplifiers. The amplifiers drove Carver Mark IV ribbon speakers, and Martin Logan CLX electrostatic speakers. I also used my Manley Steelhead phono preamplifier and VPI HR-X turntable with a Sumiko Blackbird MC cartridge. Cables were Wireworld.

Moving the power amplifiers around took me a long time, as the Emotiva and Classé are in the 100 pound range for each monoblock, and the BAT-VK-75SE is also very heavy. The Xs-300’s are 300 pounds each, so they stayed in place with the Carver speakers. Thus, I was not able to use every amplifier with both sets of speakers.

I used a line stage gain setting of 0 dB for most of my listening, as this gave the lowest noise floor (see bench tests). There are four settings: 0 dB, +6 dB, +12 dB, and +18 dB. What these settings do is increase the output relative to the input, so you can choose a setting that gives you a lot of play on the main volume control, or very little play.

In general, I found that the Mark Levinson N^o52 was very neutral, as one might expect from the bench tests. It produced absolutely no color of its own, adding or subtracting nothing. As to the pairing with power amplifiers, the Classé CA-M600’s were neutral as were the Emotiva XPR-1’s. The Pass Labs Xs-300 amplifiers were warm, and the pairing with the BAT-VK-75SE gave the most warmth. The preamp sounded good with all of the power amplifiers, but its extreme neutrality allows you to choose further neutrality with the power amplifier, or to have a pairing that delivers a warm sound, one that many consumers really like, and in fact, I preferred the N^o52 with the BAT-VK-75SE, which has a lush midrange.

The Steve Wilson quartet is a modern group that plays jazz in the classic style, with sax, piano, bass, and drums. It’s the kind of music I like to play myself. Listening to this album (Stretch Records – 0-1343-19019-2) was a pleasure using the N^o52. Steve’s sax, whether Alto or Soprano, seemed to materialize in front of me. Ben Riley’s ride cymbal had a sheen that is very difficult to reproduce in recordings, but there it was, a result of the amazingly low noise floor of the N^o52. Bass was tight and twangy, piano was natural, crisp, and full-bodied.

Jean-Philippe Rameau wrote these Keyboard Suites for the Clavecin (Harpsichord), but this particular album (Hyperion – LC7533) has them played by Angela Hewitt on the piano. The piano is a difficult instrument to play, and just as difficult to record, because like the human voice, we know exactly how a piano sounds, so if something is not quite right, we know it immediately. Hewitt’s interpretations of the pieces were beautiful, and the individual notes and chords (striking one or several keys at the same time) sounded as natural and life-like as I have ever heard. If something in the signal chain has a lot of IM, the chords will sound mushy, but they were very clear and detailed with this setup.

Most of Secrets’ readers know that I love the Baroque period, and I collect albums wherever I can find them. The concerto is my second favorite composition style (my favorite is string quartet chamber music), and this album of Torelli Concertos (Chandos – CHAN0716) contains concertos with both string (violin) and brass (trumpet) soloists. Strings are another instrument that gets very mushy with high IM in the signal path, and trumpet can sound harsh if there is signifcant amounts of high order harmonics, neither of which I heard with the N^o52. The violin soloist stood out from the rest of the instruments very clearly, and each note of the solo parts was awash with detail and musicality. The trumpet did not glare, but rather, glistened with mellifluous sweetness (damn, I wish I could have used adjectives like that when I wrote scientific articles for medical journals).

Nothing like Bach and Haydn to let you know you are listening to “High End” composers of the Baroque period. In this case, it was Hadyn’s Symphonies No. 92, 94, and 97. The No 94 is also known as The Surprise symphony, because it starts out with sort of a soft melody and then the last note at the end of the opening phrase is ffff .  It’s a very dynamic piece to say the least, and fortunately, it’s in the SACD codec. It was also fortunate that I had several very high power amplifiers on hand, because the N^o52 didn’t flinch. It was a bit too much for the VK-75SE, which only has 75 watts RMS per channel output. That’s the deal with tubes though. If you want 500 watts, you will have an amplifier with a square meter of tubes staring at you with their filaments aglow, and you will need to wear a T-shirt to absorb the perspiration from the heat. So, I ended up settling on the Xs-300’s as the best power amplifier choice for the Haydn symphonies.

I used the N^o52’s phono preamp with a whole bunch of my classic jazz albums that had been remastered and recut at 45 RPM. The N^o52 has a lot of choices to load your phono cartridge, but there is no critical combination of resistive and capacitive loading. You can play around with the various choices in the menu, and let them stay where you like the sound best. In fact, I have several setups for the loading on my own phono preamp, the Manley Steelhead, depending on the album. In this case, I preferred the Steelhead’s tube sound quality to the N^o52’s neutrality.

The Mark Levinson N^o52 Stereo Preamplifier On the Bench

Distortion measurements were within an 80 kHz bandwidth. I used the XLR balanced inputs and outputs for the measurements. The volume control was set to 80. The gain setting was at 0 dB, unless otherwise noted.

At 2 volts output, THD+N was a vanishingly low 0.00041%. All of the visible harmonics were at or near – 120 dBV. Distortion this low is totally inaudible.

The graph above was with a gain setting of 0 dB (in the Line Stage Gain menu). This produced 2 volts output with a 2 volt input signal. The three graphs below show what happens when the input remains at 2 volts, but the gain settings are changed to +6 dB, +12 dB, and + 18 dB. You can see that with each increase in 6 dB, the output voltage doubles. The distortion difference (0.0001%) between all four graphs is insignificant. The noise floor does go up with increasing gain settings, and that is why I decided on 0 dB for the setting. It also gave me a volume control play all the way up to 80 dB. However, it was too loud for my listening preference with the volume control above 75 dB. If you obtain a N^o52, start with 0 dB in the gain setting menu and then work your way up until you have the volume control play that you want, because even at +16 dB gain setting, the noise floor is still only at -120 dB, which is inaudible. 

At 5 volts output, distortion was even lower. In fact, this is near the limits of the Audio Precision test instrument. The harmonics are near – 110 dBV, which are still inaudible.

Using 19 kHz and 20 kHz sine wave test tones, the B-A peak at 1 kHz was at – 120 dBV. Only two side bands (one on either side of the two test tones) were visible.

At 5 volts output, the B-A peak at 1 kHz was at – 115 dBV, which is inaudible. Two side peaks on either side of the test tones were visible, which is continued astonishing performance.

IMD at 2 volts output was below 0.001%. The base of the 7 kHz test tone peak does not have much side band data (in some amplifiers, there is a pyramidal shape to the base, indicating more intermodulation with the 60 Hz test tone that is part of the IMD spectrum). The second harmonic at 14 kHz is below audibility.

Raising the output to 5 volts resulted in no significant change in the IMD (a difference of 0.0001% is not significant). The noise floor did rise, but this is common, and the noise floor is still below – 120 dB.

A Hum Spectrum is shown below. The X and Y axis have been expanded to show details at 60 Hz and its multiples. The highest one I can see is at 420 Hz, but, in general, they are all buried in the noise floor. The N^o52 has a superb power supply. 

The measured frequency response was 10 Hz to 200 kHz, – 0.4 dB, which is spectacular ! ! The response with the stress load of 600 ohms was identical to the response with the 100 kOhms test load.

The adherence to the RIAA curve was flat to 30 kHz. I used 7.7 ohms and 200 pF capacitance as the load.

The THD+N vs. Frequency test indicated that distortion at both 2 volts and 5 volts output stayed below 0.0005%. So, distortion at all audible frequencies was essentially negligible. In 20 years of editing Secrets, I have never seen performance like this.

THD+N vs. Output Voltage showed that distortion in a typical range (500 mV  – 5 V) stayed mostly well below 0.001%.

Conclusions about The Mark Levinson N^o52 Stereo Preamplifier

I have reported on many preamplifiers at Secrets, and said good things about most of them, great things about a few of them, but words are not really needed when the bench test data show such amazing performance. The Levinson engineers did a fantastic job building, “the best preampifier they have ever designed”.

It’s a beautiful product to show off, an amazing product to listen to, and it’s not even the most expensive preampifier out there. If you are a Levinson fan, you may have already ordered one of the N^o52’s, and if you are someone who has been thinking about becoming a Levinson owner, now is the time. I can’t think of any more adjectives to express my admiration for the Mark Levinson N^o52 Preamplifier. Well done ! ! !

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Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier Review Highlights

The FET Valve CF Vacuum Tube Preamp is a highly flexible little component. The base unit has six analog inputs, a tape loop, two line outs and a nice headphone amplifier. Possible upgrades include a remote volume control, a phono stage, a buffered tape out and a theater bypass switch. The preamp can also be ordered in either black or silver. So you can see that it is the type of component that will grow with your system

The only transistors in the box are used for power regulation. There are no transistors in the signal path. It is an all-tube design with a lot of line gain and an unwavering ability to feed just about any amplifier I can imagine. The sound is grain-free and detailed with just a touch of tube sweetness. The build quality is above what one would expect at this price point and the bench test results are quite strong for a tube component.

Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier Highlights Summary

• Solid build quality
• Plenty of inputs (6)
• High gain design
• Smooth, grain-free sound
• Excellent bass response
• Very good channel separation
• Lots of customization options

Introduction to the Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier Review

Audio by Van Alstine has been making high quality audio equipment for the better part of 40 years! They have a reputation for building solid, affordable amplification components. They have not expanded too much over the years and this means their customers enjoy a personal touch in dealing with the company. Odds are pretty good that Frank Van Alstine himself may well answer your emails or your phone call. I love this type of company because it means that the owners have a direct and personal commitment to their customers in terms of product quality and long term support.

Even though the company has been in business a long time, the following review of the FET Valve CF Vacuum Tube preamp represents my first opportunity for a long-term involvement with any Audio by Van Alstine product. I was quite excited the day the review unit showed up and my excitement didn’t waver one bit during the review as the preamp performed flawlessly during the evaluation period. Briefly, the line stage section is an all-tube design predicated on a cathode follower architecture. This means it is tolerant of difficult loads, has wide bandwidth and high gain. My review unit was packed with almost every available upgrade including the silver faceplate.

Design and Setup of the Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier

The Audio by Van Alstine FET Valve CF preamp is the next evolution of their highly regarded and award-winning FET Valve Hybrid Preamp. The biggest advancement is that the new FET Valve CF unit has an all-tube signal path where the prior model was a hybrid design.

Audio by Van Alstine claims that the updated preamp uses premium parts throughout to include precision volume and balance controls, a precision source selector, polypropylene capacitors in the signal path and multiple MOSFET-regulated power supplies.

The included tubes are a pair of 12AT7’s used for gain and a pair of 12AU7’s which serve as the cathode followers (CF). CF designs are said to be particularly tolerant of demanding loads. Additionally, well-executed CF designs offer low distortion and wide bandwidth with particular improvements in the bass.

My review unit had the silver faceplate and was packed with several of the available upgrades. Let me give a broader overview of the preamp before going into my description of the optional upgrades.

The sturdy front panel is machined from ¼” anodized aluminum. The clean look is dominated by three large knobs on the left. These are the input selector, the volume control and the channel balance knobs. Each of these controls has a tight and confident action.

There are two clusters of two pushbuttons above the main control knobs. These buttons are the Tape Monitor Selector, a Stereo/Mono Selector (nice), a “Low Gain” Toggle and a “Filter” button. The Low Gain switch reduces the gain when depressed and is used if the source doesn’t need a lot of gain and/or to allow greater selectivity of the volume control. I used the Low Gain setting a lot, especially with my Oppo BDP-105D which has a high output level. The Filter switch engages a filter that subtly reduces the low bass and the very high frequencies. I used this to tame the screechy highs on some older vinyl and also to reduce the bloat on some modern recordings. It can also be used as a rumble filter for your vinyl sources. The effect was subtle but useful and it is good to know that Van Alstine can tailor the frequency and slope of the filters on request.

On the right side of the faceplate are the power indicator, remote IR pickup, the ¼” headphone jack and the On/Standby switch.

In the back you will find a ground lift switch, 6 pairs of RCA inputs, a stereo tape in and out along with two sets of unbalanced outputs. Again, the parts quality and workmanship are of a very high order particularly when you take into account the reasonable price. This little preamp represents a no-nonsense design and execution in just about every respect.

Let’s talk about the included upgrades that came with my review unit. The “biggest” upgrade would be the optional remote control. For an extra $299, Van Alstine will include what is in essence a remote volume control with a motorized volume pot. Take a look at the image of the remote. This is my kind of remote! (Although it may be the most intuitive remote ever invented, you would be surprised how many of my friends studied this clicker very closely before adjusting the volume. I was flummoxed, what else could this remote possibly do?)

The next upgrade is a $249 phono stage that Van Alstine describes as an “outstanding brand new split passive EQ optional phono section with its own isolated regulated power supplies.” This add-on has flexible loading options (factory-set) and takes up Input 1 when installed. My reference cartridge is the Sumiko Blackbird which is a high output MC design that uses similar loading as an MM cart. This phono stage proved to be way better than I expected and I have a lot to say about it in the “In Use” section to follow.

Here is how Van Alstine describes the included power supply – “The power supply consists of a multi-tapped shielded toroid power transformer, a high voltage diode bridge and six isolated high voltage active regulators, one for each half of each tube section (the cathode followers run both halves in parallel). There is a separate regulated power supply for each channel’s tube heaters. If any solid state option is ordered (phono, tape buffers, or inverters) two additional low voltage regulated power supplies are installed. An additional regulated power supply drives the remote control board, and there is one more for the mute circuits.”

One last point is that the FET Valve CF Preamplifier has a built-in speaker protection network that provides a 30 second time delay at turn-on and an instant disconnect at turnoff to suppress switching transients.

The Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier In Use

From an operability standpoint, the AVA FET Valve CF preamplifier was about as simple as could be. It is a straight forward design with many useful features. I used many of the features on a regular basis.

Of the included features, I used the Low Gain switch most often. This was due to a number of reasons. First off, some of my sources have pretty high level outputs like the aforementioned Oppo BDP-105D. Secondly, the FET Valve CF preamp has gobs and gobs of gain. It is nice to have this much gain. It means that your preamp circuitry is operating well within its design envelope. Lots of gain is also useful in the event you need it for weak source components or poorly mastered material. But I found most of my sources did not need all the available gain so the Low Gain switch remained engaged a majority of the time.

Another point on this topic – AVA claims that the circuit design of the FET Valve CF Pre is so pure that you will find yourself playing back your music at lower volume levels due to the increased clarity. They are definitely right about that. I wound up keeping the volume lower than usual while still hearing all the intricacies in my music. The Low Gain mode allowed for a wider range of volume selectivity at these low levels.

I also used the Filter Circuit once in a while. In so doing I was typically trying to take some of the sizzle out of period recordings or trying to reduce the bloat on some more recent recordings. I also used it as a rumble filter on warped records.

One little problem I had with this preamp was with the Mute function. There is no mute switch on the chassis so the remote is the only way to mute the output. Since there is also no visible indication that the mute is engaged, there were times when we would check the input, the source, the amp, pretty much everything else until someone remembered that we had pressed the mute button on the remote. It’s OK for you to laugh at this, but it happened more times than I would like to admit.

I started my listening evaluation by testing the headphone amplifier over a pair of Onkyo ES-HF300 headphones. These phones are a relatively easy load and the AVA didn’t miss a beat. I particularly loved the sound I got listening to a high resolution download of Beck’s “Morning Phase” album through my Oppo player. The AVA and Onkyo combo brought forth the bass in a strong supporting role and with more nuance than I have heard before. I also tried the headphone amp with some Paradigm Shift E3m ear buds and enjoyed the AVA’s smooth, extended presentation. The only thing I didn’t like about the headphone amp is that using it didn’t automatically mute the line level output. You must remember to turn off your power amp.

I will lead off the discussion of the preamp as a linestage by evaluating Allison Krauss and Union Station’s most recent album “Paper Airplane”. I bought this album on heavy vinyl when it first came out. Frankly, I haven’t liked what I’ve heard from this record audio-wise. The fidelity has been something of a letdown. So I was most pleased with what I heard when I listened to it through the included RIAA input in the FET Valve CF preamp.

The first thing to strike me was that it sounded much cleaner and better balanced than what I have heard in the past. Krauss’ voice was as pure as I imagined it should be. And on the tracks that call for it, the bass thundered without obfuscating the upper registers.

Then I noticed that there was a seamless spread across the front that was much wider than the speakers’ separation. Though it was wide, the stage did not lose any of its placement specificity and this was heard clearly on “On the Outside Looking In” where Dan Tyminski’s voice emanated from a black space, floating in the middle of the room.

After this, my notes just say that the AVA RIAA EQ “respects your music”. I then sat back and just listened.

Next up was The Who’s great classic “Tommy” which was recently reissued by Quality Record Pressings. Thankfully, this new record is not gratuitously compressed like so many other iconic rock albums.

There were two aspects of the sound that were about the best I have heard from my Blackbird cartridge – the channel separation and the bass extension. The Van Alastine preamp really let my vinyl front end shine in these areas. But that was not all. The overall sound was at once smooth and dynamic. And Daltry’s voice had a fleshy presence like hearing him in person. The phono stage in the AVA preamp is among the best affordable phono preamps I have heard.

Now I wanted to listen to some more digital fare so I fired up my Blu-ray player and inserted my Phantom of the Opera 25th Anniversary at Royal Albert Hall disc. This disc’s audio and video are both reflective of a very high production standard. One reason it sounds so great is that all the singers are mic’d, including the chorus.

The FET Valve CF’s strongest quality on this disc revolved around the high gain which led to unrestricted dynamics. (The gain can get away from you on louder passages sort of in the way a sports car’s tires might break up if you aren’t paying attention.) You need to find the right set point so the loud passages stay within the capability of your amp and speakers. When the volume control was set to an optimum level, the AVA preamp really let the lively dynamics flow on this disc.

The staging was a highlight once again with the soloists’ front and center while the orchestra painted the edges. The stage depth was still better than average if not the best I’ve heard. With the dynamics, the staging and the smooth accuracy of the FET Valve CF, “Music of the Night” gave me goose bumps despite that I have heard it a thousand times before.

It all snapped into focus on the “Jack Ryan: Shadow Recruit” Blu-ray. As with the Phantom disc above, I needed to play with the gain a little to find the “right” volume level. And once I found it, then the whole of the presentation came to offer a deep audible experience. Not just in the extremes, as it is, but also in a sense of spatial reality. There was bass extension that went on forever with a warm yet fresh sound up top. The mids were simply golden and eerily lifelike. It’s at times like this where adding surround would be a purely frivolous effort.

The Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier On The Bench

The first test I ran was a 1 kHz sine wave at 2V RMS. THD+N measured just 0.00381% with the first harmonic being 90 dB below the test tone.

Still tested at 1 kHz, but bumping the output to a blazing 5 Volts (14 dBV) RMS, the FET Valve CF’s THD+N rose to 0.00862% and the first harmonic was 83 dB below the fundamental.

This is the Intermodulation Distortion Test with signals at 60 Hz and 7 kHz. The measured IMD at 6 dBV (2 Volts) came to just 0.0028%.

This is the other IMD Test we run with signals at 19 kHz and 20 kHz. The B-A peak is 90 dB below the signal at 2 Volts output.

This plot shows the frequency response of the FET Valve CF at 2 Volts output. Notice the scale of the vertical axis is highly exaggerated in order to make the response curve easier to see. The response is within 0.25 dB of flat from DC to 20 kHz. It continues to roll off from 20 kHz to 90 kHz at which point the response is 1.4 dB below the 1 kHz level.

Conclusions about the Audio by Van Alstine FET Valve CF Vacuum Tube Preamplifier

I highly recommend the Audio by Van Alstine FET Valve CF Preamp. It is an all-tube design that isn’t crazy expensive like so many competing products on the market. It has been designed with care to perform in just about any system I can imagine. And the sound is not overly mellifluous as one may wrongly expect based on the tube design. Instead, you get a sound that is accurate, extended, clean and with lifelike transient response. Sure the tubes add a touch of the golden hues tube lovers crave, but that doesn’t define or dominate the sound you hear. It’s simply a natural smoothing of the rough edges adding a nice bloom to what you hear. The FET Valve CF Preamp is also capable of excellent staging in both width and depth.

Another strong point is the flexibility of the unit. Six inputs, two outputs and a tape loop. Plus you can customize the unit with so many available options. You could start with the base unit and then upgrade later if you have real-world budget problems like the majority of the population. But I would strongly advise those with turntables to order the phono stage with their FET Valve CF Preamp. This phono stage in and of itself may be the best value in audio that I’ve heard this year.

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Emotiva XPS-1 Phono Preamplilfier Review Highlights

With the resurgence of vinyl over the last few years, more and more enthusiasts are looking to get in the game to see what all the buzz is about. Now there is another affordable way to incorporate records into your existing system and it comes from none other than one of the premier affordable audio companies on the planet, Emotiva. Their little phono stage, dubbed the XPS-1 is compact, well made and universally adaptable to any system. The sound it produces is vivid and upbeat with very low background noise.

Emotiva XPS-1 Phono Preamplifier Highlights Summary

• Review Highlight Points
• Excellent build quality
• Mates well with all types of cartridges
• Low noise
• Wonderful sound staging
• Vivid, lively and upbeat presentation

Introduction to the Emotiva XPS-1 Phono Preamplifier Review

Emotiva is definitely within the league great high end audio companies of the 21st Century. Their products are serious pieces of audio engineering: well designed, solidly built and not bad to look at. And did I mention they usually sound terrific? So you may think, “What’s all the fuss about? A lot of companies produce decent high end products.” That would be true, but nobody else does it at similar price points. Emotiva really does offer you champagne tastes for your beer budget.

Enter their newest product, the XPS-1 Phono Preamplifier. This tiny component allows hook up of moving magnet or moving coil cartridges. But unlike other budget phono stages, the XPS-1 accommodates different loading requirements for your MC cartridge. This makes it a universally adaptable product that will never become obsolete. The bigger question is how does it sound?

Design and Setup of the Emotiva XPS-1 Phono Preamplifier

Emotiva’s diminutive XPS-1 phono preamp is a highly flexible unit in a small form factor that is surprisingly well built for its price class. The case is just a bit larger than a pack of cigarettes with unbalanced ins and outs on opposite sides of the case. These are via high quality gold plated solid brass RCA connectors. The gold plated ground terminal is on the same side as the inputs while the DC power input is on the side with the line outs.

The blue power indicator LED is on top of the case. Like many similar products, the XPS-1 is intended to remain plugged in and powered up all the time. The idling power consumption is very low.

All the controls are also on top of the case. These include a pair of toggles to set the gain for either moving coil (60 dB) or moving magnet (40 dB). There are also two rows of DIP switches for selecting the input impedance of your MC cartridge. Possible impedances are 1 k?, 470 ?, 100 ? or 47 ?. These are all common values to match your cartridge’s loading requirements. If the MC/MM toggle is set to MM, then the input impedance is fixed at the industry standard 47 k? for a moving magnet cartridge. All this represents an alarming degree of flexibility for a product in this price class.

The XPS-1’s case is a rugged all-metal design that offers enhanced immunity from noise and electrical interference. This type of shielding is particularly important for phono preamps as they must manage and amplify very small signals, particularly when fed via a low output moving coil (MC) cartridge.

Emotiva claims that the XPS-1 has sophisticated multi-stage power supplies for “superior noise performance”. My experience holds that well-engineered power supplies pay off with audible improvements and I will have more to say about this in the In Use section to follow.

Emotiva has further claims regarding the measured performance of this product. This includes an accurate RIAA equalization of +/- 0.25 dB along with claims of low noise (high signal to noise ratio), low harmonic distortion and exceptional channel separation. These claims are supported through rigorous, independent testing by Audio Precision that can be downloaded from the Emotiva website – Audio Precision Tests XPS-1.

Setup was a breeze. You make the line-level and ground hookups, set the gain and load impedance and connect the power supply. Then you are ready to start listening. The XPS-1 is also great for those users who like to play around with the load impedance to fine tune the sound to their liking. So there is some room for experimentation after the initial hook up, but most everyone will be listening to their favorite records in no time flat.

There were only two things I didn’t like about the physical design of the XPS-1. One was having the inputs and outputs on opposite sides of the case. This required me to curve one set of interconnects for my particular setup. I also thought the power indicator was unnecessarily bright.

The Emotiva XPS-1 Phono Preamplifier In Use

My experience with amplification products of all types has led me to the conclusion that well-engineered power supplies tend to support the drive in music. This is communicated by an energetic boogie factor that was the XPS-1’s calling card throughout the audition period.

This was heard quite well when listening to Cannonball Adderley’s classic “Somethin’ Else”. I have a heavy vinyl reissue of this record that just sounds marvelous over proper playback equipment. So speaking of boogie factor, I heard it in spades through the sax solo/lead on “Love for Sale”. This part also showed an addictively vivid rendering. The bass was decidedly tame but with lots of space between the notes that helped propel the beat.

Compared to the best phono stages I’ve heard, the XPS-1 was a touch chalky sounding with an ever so thin presentation in the treble. Still, the cymbals stayed just on the warm side of neutrality so the realism factor remained intact. All in all, the XPS-1 showed its mettle time and time again by keeping everything in its place, even when things got heated up. It kind of impressed me, a lot.

Speaking of boogie factor and complex arrangements, why not pull out another stellar reissue – Buddy Guy’s “Stone Crazy!” on Alligator Records. This is high octane, nearly incendiary material with Buddy’s regular band of the day (1981). Recorded in France, the album is meant to mimic one of his live shows and is chock full of rockin’ guitar licks! The Emotiva XPS-1 joined the party and laid down a rollicking performance complete with driving bass, edgy electric guitar and rhythmically precise drum work.

The XPS-1 offers a musical perspective I found to be program-dependent and in this case it was like an intimate live setting in a small Chicago bar. Another nicety was the low-noise performance of the XPS-1. Take “When I Left Home”. It started off with a soft passage and the background noise level was audible but not intrusive. It simply reminded me that this was vinyl but this light touch of noise wasn’t screwing up the music. Then once the band set off full bore, the dynamics were free of any audible limitation.

The little Emotiva also did an excellent job of handling vocal sibilants where lesser designs might over accentuate them or they may fuzzy or hard-edged, the XPS-1 did them very naturally. My final analysis of this album was that Buddy can really shred it and thank you Emotiva for facilitating this decadence!

Next up was Tchaikovsky’s “The Sleeping Beauty Ballet Suite” by The Philadelphia Orchestra with Eugene Ormandy conducting. This was an original pressing on the Columbia Masterworks label. The slight chalky quality I mentioned before was not apparent on this disc. This quality would come and go but slowly diminished over time and I think it might just fade away all together given enough break-in.

The sonic highlights on this album involved the stage width, dynamics and the ability to sort complex passages. Starting with the stage width and perspective, these qualities were program dependent through the XPS-1 and with this record; I was in the first row. My favorite parts of this album were when the whole orchestra was playing at once and the XPS-1 did a very good job of managing the complexities.

I’ll close out my listening impressions with Leo Kottke “6- and 12-String Guitar” on heavy, clear vinyl. This is Kottke’s most famous album and showcases his original finger-picking style on guitars fitted with steel strings. It is a true masterwork and I could hear deep into the music with the Emotiva in play.

Again, the sound from the XPS-1 was vivid and lively with a balanced frequency response that was warm but responsive. The fast-paced picking style brought out the strength in the Emotiva. The music was played with confidence by the artist as well as by the system.

Side 2 started off more lyrically and playing this back was a total breeze for the tiny Emotiva. There was some audible surface noise here but the XPS-1 was able to avoid it intruding on the music. I am not sure exactly how Kottke played these songs to develop all the amazing guitar sounds but it is definitely something to behold. Now was the time to just enjoy.

Conclusions about the Emotiva XPS-1 Phono Preamplifier

Well, there you have it. A $149 phono stage with all the flexibility one could ask for. So of course it isn’t going to sound very good, right? Well not so fast! This little guy has a vivid, lively and upbeat sound with agile bass response. The vocal sibilants are impressively clean as is the channel separation. The audio performance does improve with break in and I would log at least 50 hours on mine before passing judgment.

You can also expect great build quality in its compact form factor. The all-metal case and gold-plated connectors make the XPS-1 look like a little piece of jewelry. The Emotiva XPS-1 is a clear cut recommendation as a high value add-on for those without a phono preamp or as an upgrade for those with included phono stages in mass market receivers.

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ATI AT6002 Multi-channel Power Amplifier Review Highlights

The ATI AT6002 is a fully balanced amplifier that produces 300 watts per channel into 8 ohms and 450 watts into 4 ohms. The fully balanced design reduces THD while increasing SNR, and it is an innovative amp that offers incredibly high performance.

ATI AT6002 Multi-channel Power Amplifier Highlights Summary

• Two-to-seven channels as a choice
• 300 Watts into 8 ohms, 450 watts into 4 ohms
• Fully balanced, dual-mono design
• Incredible power reserves with dead silent backgrounds
• Very heavy to move

Introduction to the ATI AT6002 Multi-channel Power Amplifier Review

You may be familiar with Amplifier Technologies, Inc. (ATI), but perhaps not with its founder and designer, Morris Kessler. Since Morris started building amplifiers at age 18, he has been designing some of the more innovative amplifiers in the A/V world. ATI also builds amplifiers for other companies, such as Theta Digital, Dynaco, Adcom, Aragon, Crestron, and more.

Now comes the first amplifier to bear his signature on the front panel, the ATI AT6002. A fully balanced, dual mono amplifier with high-end build quality, the AT6002 feels like a statement product. Even better, it sounds like one as well.

I’ve never felt as bad for my FedEx delivery person as I did when the AT6002 arrived. It isn’t the largest package I’ve ever received, not by far, but it might be the most dense. It took the two of us just to get it from the truck to the front steps. Moving the amplifier from the living room into the basement was much easier by utilizing the rack mount handles on the front panel.

Design of The ATI AT6002 Multi-channel Power Amplifier

The AT6002 design is unusual for ATI. For one, it is a true dual mono configuration. There are two amplifier modules, two power cords, and even two power switches. There are also dual toroidal transformers in the front, which help contribute to the massive weight of the AT6002. The modular nature of the AT6002 puts the two amplifier channels on their own cards. This allows ATI to use less point-to-point wiring, which can be a common point of failure, and rely more on PCB boards for reliability. It also allows taking a single channel of the amplifier out and replacing it if necessary.

This daughter-board design allows the AT600x lineup to support between two and seven channels. The $3,995 AT6002 has two channels, capable of 300 watts into an 8 ohm load and 450 watts into a 4 ohm load. The $7,995 AT6007 delivers the same power, but into seven channels instead of two. With dual AC inputs, each capable of a 20 amp load from an individual circuit, there is plenty of power to drive the AT6007.

There is far more to the internal design of the AT6007 than what I am presenting here, but in the Bench Test section, Dr. David A Rich will take you through the design choices made along with the Pros and Cons of each.

On the outside, the AT6002 is simple. Finished in a powder coat black, the front has rack handles to let you position this incredible beast. Each channel has RCA and XLR inputs with a switch to choose between them. A 12V trigger input lets you have it power on with your preamp or receiver. Five-way binding posts for each channel accept banana plugs, spades, or bare wire.

Impressively, the AT6002 design lets you update it down the road if you desire. Additional channels can be added for $800 each, with the work done at ATI. Since the upgrade requires new transformers and a new rear panel, it cannot be done at home. With no price penalty, other than shipping fees for doing the upgrades down the road, it provides you with security if you want to start with fewer amp channels at first.

I did most of my testing of the AT6002 with a pair of Revel f208 speakers. I used a wide variety of source components to test both RCA and XLR inputs. A Marantz AV7005 and Anthem MRX 510 was used with RCA inputs, while the AURALiC Vega DAC, AURALiC Taurus Headphone Amp, and Oppo BDP-105 Blu-ray player were used with XLR inputs.

The ATI AT6002 Multi-channel Power Amplifier Review In Use

No matter how much power any amplifier has, there is a limit to how loud we can listen to it at. Despite this limit, the ATI AT6002 has the largest dynamic range of any amplifier I have ever heard, because when it is quiet, it is dead silent. I could place my ear next to the tweeter of the Revel f208 and hear nothing when the system was idle. Not even a slight hiss. No amplifier has ever been this quiet in my system. The amplifier itself is also as quiet as can be (no noises made by the physical structure). There are plenty of amplifiers that produce a slight sound in use, though it is usually buried under the music. The AT6002 is so quiet, you wouldn’t know it was on if not for the LED light up front.

Using the AURALiC Vega to deliver the new Led Zeppelin high-resolution masters, the AT6002 pounded through these classic re-releases without issue. From the opening chords of “Whole Lotta Love” to the final notes, every note was clear and precise. The dual 8” woofers of the Revel f208 strain receivers, even high-end ones, when pushed to high output levels. The AT6002 had no problems here, and there was no harshness or break-up as it powered through the best of Plant, Page, Bohnam and Jones.

ATI also states that the design of the AT6002 is for the demands of modern film soundtracks. So why not push the volume all the way to reference levels (85dB with 105dB peaks) and listen? When the opening Kaiju attacks San Francisco in Pacific Rim, a deep guttural roar filled my listening room and scared the hell out of me. Having seen this film a dozen times, it shouldn’t surprise me anymore, but it managed to do so by filling my room in a way it hadn’t been done before. The roar even managed to wake up my kids, sleeping two stories above.

With female vocals, the AT6002 brought out the clarity of their voices. Compared to my Parasound Halo A31, the ATI AT6002 removed a layer of granularity. Like a pale warm sky at dusk, vocals were a little bit smoother than before. Natalie Merchant’s vocals in Carnival offer a bit more than I’ve heard before, and I listen to the track at least once a week. The A31 is already a good amplifier, but the AT6002 offers just a little bit more resolution than it does with the Revel f208.

A unique aspect of the AT6002 is how much reserve power it has. Even after I switch the amplifier off, it will continue to play music for a good 10-15 seconds just off the extra current stored up. This amp is as overbuilt as a 110 pound movie starlet with 6 pounds of breast implants. With ttge AT6002, you worry about the glassware falling out of the wine rack, not the amplifier running out of slam.

I tried to push the AT6002 as much as I could, including tracks from the metal band of all metal bands, Metallica. No problem. Massive Attack and their repeated 40 Hz notes into the Revel f208? Child’s play for the ATI. Miles Davis and a double bass? Why don’t you keep turning up the volume, I don’t mind. Morris Kessler plastered his name on the front of the AT6002, so I knew I could put the pedal to the metal. I just could not make the amplfier lose its cool.

The ATI AT6002 Multi-channel Power Amplifier Review on the Bench

By David A. Rich Ph. D.

We want to thank Audio Precision for the loan of the test equipment used in this review. Chris Heinonen did the measurements.

AC Watts are measured in average power rather than RMS. Only AC current and AC voltage are RMS quantities.

All numbers in this report are for the worst-case channel. Channel match in these tests was excellent.

The noise level of the amplifier is very low. We measured 17.8µV of noise at the speaker terminals with the input grounded. This measurement was flat from 20Hz to 20kHz. Using this noise value, the SNR can be calculated to different reference values.

SNR 95dB at 1VRMS
SNR 104dB at 1 Watt into 8 Ohms (2.8VRMS)
SNR 128.7dB at 300 Watt into 8 Ohms (49.2VRMS)
SNR 127.6dB at 470 Watt into 4 Ohms (43.3VRMS)

The 128.7dB SNR at 300 Watts has a bit equivalent of 21 bits, which is better than any DAC now on the market. As you can see, the numbers go up at full power, and this will vary with the maximum voltage the amplifier can swing before clipping The ATI 6002 can swing 50VRMS. Using the standard 1 Watt reference, the SNR is still remarkable high. Again I point out these are not weighted numbers. Every noise source in the amp’s first gain stage has to be carefully considered to achieve these noise levels.

The gain of the unit with RCA in was 27.1dB (22.55V/V)

The frequency response at 8 Ohms is shown below. It is ±0.22 dB

The crosstalk in the worst channel at 10kHz was -101.966 dB.

AT6002 Power Output into 8 Ohms

At 310 Watts (50VRMS), the THD into two channels was 0.012%. THD+N was also 0.012%, reflecting the units low noise. The spectrum is below:

We note the odd-ordered harmonics are significantly larger than the even-ordered harmonics, as expected for a balanced amplifier. The origin of the small spurs, which are spaced at 120Hz (the full wave rectifier fundamental frequency), is not clear. Note that the side tones are on the fundamental test tone frequency (1kHz) and the odd-ordered harmonics.

Given the importance of the distortion structure in the balanced amplifier, I have listed the harmonics below. The odd harmonics are dominating out to the 9th harmonic.

1.0k 2.0k 3.0k 4.0k 5.0k 6.0k 7.0k 8.0k 9.0k 10.0k

-0.00 -94.80 -80.75 -112 -95.76 -129 -89.26 -133 -89.03 -135.83

Below is a spectral plot under the same conditions from 0Hz to 1kHz, to illustrate any hum spurs.

No power supply hum spurs are seen above -135dB, a remarkable result for a power amp at full power. Two spurs at 780Hz and 880Hz are the full wave rectifier fundamental frequency (120Hz) modulating around the 1kHz test tone. The origin of these modulation spurs is unclear and may be at the experimental site.

IMD, using 19kHz and 20kHz, was 0.086% for the first 3 IM products in the worst case channel.

The individual products are shown below. The 1kHz the 2^nd order IM is very low, but the 3^rd order IM tones at (18kHz and 21kHz) are higher than expected. ATI provides no specification for this test.

The 2^nd harmonics of the tests tones (38kHz and 40kHz) intermodulate with the 19kHz and 20kHz test signals to produce the 3^rd order 18kHz and 21kHz IM tones (do not confuse the order of the IM tones with the order of the harmonics). The 2^nd harmonics of 19kHz and 20kHz were down -80dB, so it is unclear what is causing 3^rd order IM tones to take on the value below.

1.0k 18.0k 19.0k 20.0k 21.0k

-105 -67.92 -6.01 -6.02 -67.05

Next, we reduced the power to 12.5 Watts into 8 Ohms (10VRMS) to examine the edge of the crossover distortion region. The 12.5-Watt spectrum is below, and it indicates a very well designed power amplifier.

The THD is 0.0047%. As expected for a balanced power amp the odd-ordered harmonics dominate, and it is mostly the 3^rd harmonic at 0.0038%. The 5th harmonic is 0.0021% , the 7th 0.0011%, and the 9th 0.001%

At 3.1 Watts (5VRMS) the THD went up to 0.0051% as a result of an increase in the 3^rd at 0.0044%

The minimum THD was at 34 Watts at 0.0032%. The third harmonic drops 15dB (0.00053%) with other harmonics similar in value to the 12.5 Watt (10VRMS) spectra . The 5th harmonic now dominates at 0.002%

At 1.1 Watts the THD begins to decline again (not shown) reaching a minima of 0.0018% at 20mW. This shows low level crossover distortion is well suppressed. The origin of the bump from 180mW to 34 Watts is not clear. The maximum is 0.0052% at 1.1Watts which is still very low.

The 19kHz / 20kHz IM was 0.023% for the first 3 IM products in the worst case channel at 12.5 Watts. The individual products are shown below. The 1kHz 2^nd order IM is very low but again note the values of the 3^rd order IMs.

1.0k 18.0k 19.0k 20.0k 21.0k

-121 -79.13 -6.0 -6.0 -77.61

For the 34 Watt level, which yielded the minimum THD the 19kHz / 20kHz IM was 0.037% and at 0.023% at 3.1 Watts.

The 19kHz / 20kHz IM monotonically decreases with power but is significantly higher than the 1kHz THD in all cases. These large differences are not typical.

AT6002 Power Output into 4 Ohms

Into 4 Ohms, the frequency response is ±0.293 dB 20Hz – 20kHz, and the crosstalk is 81.518 dB at 10kHz (both numbers in the worst channel).

The spectra below is at 470 Watts into 4 Ohm (43.3VRMS)

THD+N Ratio was 0.019% and THD was 0.019% again reflecting the low noise of the amplifier.

Again we note the odd-ordered harmonics are significantly larger than the even-ordered harmonics, as expected for a balanced amplifier. The origin of the small power supply related side tones is not clear. As in the previous case, the side tones are on the fundamental test tone frequency (1kHz) and the odd-ordered harmonics.

I have listed the harmonics below. Only the odd-ordered harmonics are significant. The level of odd-ordered harmonics does not change much out to the 9th harmonic.

1.0k 2.0k 3.0k 4.0k 5.0k 6.0k 7.0k 8.0k 9.0k 10.0k

0.0 -96.2 -77.5 -118 -84.9 -123 -83.3 -136 -83.6 -137

Below is a spectral plot under the same conditions from 0Hz to 1kHz

The 120Hz harmonic is at -130dB, a remarkable result for a power amp at full power. The origin of the two spurs, which are modulation of the full wave rectifier frequency (120Hz) around the 1kHz fundamental, is again unclear.

19kHz / 20kHz IM was 0.15% for the first 3 IM products in the worst case channel.

The individual products are shown below. The 1kHz IM is very low, but the 3^rd order IMs are higher than expected.

1.0k 18.0k 19.0k 20.0k 21.0k

-105 -62.8 -6.00 -6.00 -61.9

Next, we reduced the power to 25 Watts into 4 Ohms (10VRMS). The spectrum is below:

The THD is 0.0058 %

As expected for a balanced power amp, the odd order harmonics dominate and are significant out to the 9th harmonic.

1.0k 2.0k 3.0k 4.0k 5.0k 6.0k 7.0k 8.0k 9.0k 10.0k

0.0 -106 -87.9 -128 -91.28 -132 -94.78 -133 -97.0 -133

At 49 Watts, which yielded the minimum THD, was 0.004%. The 3^rd harmonic is down 10dB from the 25 Watt result.

At 6.2 Watts (5VRMS) the THD went up from the 12.5 Watt level to 0.0085% as a result of an increase in the 3^rd of the and 5th harmonic by 2dB

At 2.2 Watts, the THD begins to decline again (not shown) reaching a minimum of 0.0025% at 20mW. This indicates low level crossover distortion is well depressed. The origin of the bump from 90mW Watts to 49 Watts is not clear, but the 0.0084% maximum level is low.

The 19kHz / 20kHz IM was 0.035 % for the first 3 IM products at 25 Watts.

The individual products are shown below. Note again the values 3^rd order IMs (18kHz and 21kHz).

1.0k 18.0k 19.0k 20.0k 21.0k

-113 dB -76.0 dB -6.0 dB -6.0 dB -74.5 dB

The 19kHz / 20kHz IM was 0.035 % for the first 3 IM products at 49 Watts and 0.035 % for the first 3 IM products at 6.2 Watts.

The 19kHz / 20kHz IM is constant for 49 Watts to 5 Watts.

In summary, the only blemish in the AT6002s performance is the higher than expected values in the 19kHz / 20Hz IM tests, which ATI does not specify. The amplifier’s spectral performance clearly shows the advantage of the fully balanced topology, and THD at 1kHz is low, regardless of the level we looked at. The power supply hum at full power is almost non-existent, putting some preamp designers to shame. The noise of this amplifier is remarkable low, giving rise to SNR values at the 21-bit effective level of a digital component.

Design Technology in the AT6002

ATI supplied a complete schematic. I thank them for the openness they provided on the design.

This section assumes the reader is familiar with the introductory presentation on balanced amplifiers:

The Fully Balanced Power Amplifier – Advantages and Design Challenges

The ATI AT6002 is a full balanced non-inverting amplifier. As explained in the introductory article, this is the approach you need to take if you want low noise without an additional buffer stage before the amplifier.

Also, as explained in detail in the introductory article, the problem with a balanced non-inverting amplifier is that it needs two positive inputs and two negative inputs. Solutions in the IC design world do not translate to the world of discrete power amplifiers. Matching of the individual components in a discrete design is the most significant issue that must be overcome. The best discrete solution I have seen was published in the reference below and was discussed in detail in the introductory article.

Bongiorno, J. “Ampzilla III” The Audio Amateur 15.4 (September 1984): 7 – 19

Outside the complementary four input core stage, this is a pure Morris Kessler design. This is not the area of the review that I can discuss the designer of the product in detail. Morris does deserve more space than I can give here, and you can find a reference to a 16 page interview of him referenced on the ATI website.

www.ati-amp.com/about.php

Morris is a master amplifier designer you may never have heard of. He keeps a very low profile and lets the products speak for themselves. He has been producing amplifiers for 50 years.

I spent several hours at CEDIA 2012 and 2013 with Morris, discussing his general design philosophy as well as the ATI6002 circuit design in detail. This is not a circuit that gives up its secrets easily, and despite years of looking at this topology, I uncovered a couple additional aspects of the ATI6002 implementation as I studied it for this review.

Design Methods for High Reliability

What distinguishes a Kessler design is robustness. Since 1963, he has produced 500,000 units ranging from two to sixteen channels. In that type of volume you cannot afford an amplifier design that is a frequent flyer back to the factory for service.

The output stage is the area that needs the most attention to prevent a service calls. These are the transistors that drive the current to the load and dissipate the thermal losses. The data sheets for the output transistor provide complex curves to set the Safe Operating Area (SOA) of the transistor.

Cordell, B. Audio Power Amplifiers McGraw Hill, 2011, 186 – 190

Selection of a robust transistor is the first step, monitoring the output transistors’ voltage and current over time to determine if the SOA is exceeded, and the final step is stabilizing the thermal properties of the transistors. Morris has placed an emphasis on finding robust output transistors over ones with slightly better specs.

Thermal stabilization of the amplifier is significantly improved using ON Semiconductors ThermalTrak transistors which imbed the diodes of the thermal feedback on the die with the output device. Thermal feedback is much faster than when the diodes are on the heat sink. In addition, they are an exact match to the transistor. The thermal feedback is so fast, distortion of the amplifier can actually be reduced at low frequencies.

http://www.ben.cz/_d/datasheet/thermaltrak-an.pdf

A power amplifier’s unity voltage gain current amplifier stage must be designed to have good linearity. Many designs for the output stage to improve linearity exist but some can break into parasitic oscillation dependent on the load. Some nice looking designs on paper can even break into oscillation without a load connected if the transistors arriving at the shipping doc do not match parameters of the ones used for the prototype.

The Kessler current output stage design starts with a triple emitter follower configuration with a large number of passive components wrapped around the outputs to prevent parasitic oscillation. The protection circuit in the ATI6002 also senses parasitic oscillations and shuts the amplifier down. Most amplifier do not protect if a high frequency oscillation occurs on the speaker terminal.

The output stage of the current amplifier has 4 transistors in parallel. Since this is a balanced and complementary 16 transistors are connected at the two speaker terminals. 8 transistors are on each side of the speaker terminal.

In the ATI 6002 the entire amplifier is surrounded by optocouplers to the protection circuit. Information coming across optically includes the output stage current flow, output transistor voltage, and the presence of high frequency oscillations.

If any fault is detected by the protection circuitry on the other side of the optocouplers the differential pair tail current source is shut down. That brings the whole amplifier to close to zero current draw protecting itself from an external fault very quickly. Unlike CMOS analog opamps which may need extra circuits to make this work, the bipolars are frozen since they get no base current. The circuit that cuts the bias current to the amplifier is also optically isolated. At the same time, the power rails are disconnected by the standby relay. Thermal shutdown is also part of the protection system.

If the fault is outside the amp, such as a short on the speaker terminals or the output transistors were being run outside the Safe Area of Operation (SOA), the protection recycles, waiting for the user to fix the short or resolve other issues. If the problem is inside the amp, such as the rare shorted output transistor, the protection circuit senses the current flow on recycle and keeps everything off until the unit is fixed. If you power cycle the amp after it goes into protection mode, it will go through the whole process again and shut down.

Although it is rare in some amplifiers, the failure of an output transistor may take out the speaker with a large DC voltage applied across the speaker terminals. The protection is not fast enough to get the amp shut down.

The complete optical isolation of the protection system from the amplifier in the ATI Signature series amplifiers allows the eliminatioin of the relay between the amplifier output and the speaker terminals. This relay itself can be a source of failure. Note that some amplifiers are missing the relay on grounds that it affects the sound, but have not taken the steps to ensure the amplifier will not take out a speaker when the relay is removed.

The protection circuit on the other side of the optocouplers calculates how long high current has been flowing in the amplifier with a high voltage across the output devices. This condition can be the result of a complex speaker load. The protection does not activate until the SOA is exceeded. Some protection circuits are too trigger happy.

Common Mode Feedback, DC Servos and Other Circuit Highlights.

The four input core stage has the interesting property that its AC common mode rejection is high, but it has no DC rejection. Moving both input base terminals together (+ and -) will also move both speaker terminals at very low frequencies. Applying a differential DC signal to the + and – input base terminals results in a differential movement of the speaker terminals. The base terminal input pair thus allows four-quadrant control of the speakers’ DC voltage.

The common mode feedback is set by a DC servo at the speaker terminal connected to both base terminals in a negative loop. DC servos also adjust the differential DC at the output to 0. For those not familiar with DC servos, a reference is below.

Cordell, B. Audio Power Amplifiers McGraw Hill, 2011, Chapter 8

As mentioned in the introductory article, the feedback resistors at the inputs of the amp (in the non-inverting case connected to ground) must have a very low resistance values. This presents a problem. Typically a DC blocking cap will be in series with the feedback resistor to ground. This takes the gain of the amplifier from DC to 1, reducing the offset at the speaker terminal to the low level of the differential pairs’ offset. With a feedback resistor in the 100 – 200 Ohm range, the capacitor would be extremely large and introduce distortion. The DC servo, as used in the ATI Signature series amplifiers removes the need for the large electrolytic capacitor in the feedback path.

The output stages are on unregulated rails. The voltage gain stages are on regulated rails. This design approach helps reject power supply noise but can lead to problems if the power supply rails are not turned on in a proper sequence, adding additional circuitry.

The ATI6002 is fully complimentary, meaning that every PNP transistor is matched by an NPN transistor for the entire circuit. The voltage gain stage consists of the four input differential core terminated with resistors. The complementary circuit approach is essential since some DC offsets in the core are canceled. The second voltage gain stage is a standard differential pair, one on the positive rail and one on the negative rail. The complimentary collectors of the second stage differential pairs connect through the output stage base spreading circuit (VBE multiplier). The base spreading circuit, which sets the output stage bias current, uses the diodes in the ThermalTrak output devices. The base spreading circuit is also complementary in the AT6002.

Balanced to Single Ended Conversion Without an Extra Stage of Electronics

Although this amplifier is fully balanced, most users will use RCA inputs because their preamp is likely to have only single-ended RCA output jacks. The standard approach would be to add a circuit in front of the amplifier to convert the single-ended signal to differential. It would be desirable to send the one input directly to the amplifier and set the other input to ground but this will unbalance the amplifier. More closed loop gain will be on the input side rather than one side with the bases connected to ground. In the AT6002, the feedback gain is changed on the side with the grounded input to placet the amplifier back into balance. A relay switches in the resistor which balances the amplifier.

Like any single-ended-to-balanced converter, a common mode voltage will be of the amplifier’s differential pair current source (the tail). The voltage is equal to the input voltage. In balanced mode, no common mode voltage is on the current source.

Design for Low Noise

When optimizing an amplifier to achieve the 130dB SNR that we measured referenced to full power, every noise source must be considered. Most noise comes from the first stage of voltage gain. Low noise transistors are a must, but in a power amp they may see high voltages as they do in the AT6002, limiting the selection process. When designing a very low noise amplifier like the AT6002, resistors can have noise higher than expected from the thermal noise calculation. In the ATI, specially selected metal film resistors are selected for low noise.

Low noise also requires very careful PC board layout, including reducing board resistance as much as possible. Power supply regulation and decoupling must not only produce a stable DC, but they must be low noise over the whole audio band. Power supply rejection of the circuit needs to be very high, requiring all traces of the PC board to be carefully matched and shielded. In the measurements section, we saw almost no hum spurs even at full power. This is not unexpected in a design for high SNR. The fact that ATI designs its own transformers also helps here.

Conclusions about the ATI AT6002 Multi-channel Power Amplifier Review

The ATI AT6002 is completely fitting of its Signature Series designation. It is a giant in the world of power amplfiers, and I have never been so happy to have rack handles on something as I was with this. It handled all the music I could throw at it, and with its engineering pedigree and construction, I was certain it wasn’t going to break down under the stress. What surprised me is how silent it was when it was at idle.

Its modular design means it will support as many channels as any non-Atmos home theater will need. In the stereo, dual mono configuration I evaluated, I don’t have any criticism for the AT6002. It handled all my tests, from music and movies to the Audio Precision. The only problem you will likely have is moving it into place. On a positive note, for a power amplifier, heavy is good.

If you didn’t know about ATI and Morris Kessler before now, you should find out more. The ATI AT6002 Signature Series amplifier is a high-end amplifier that is designed to please and never be replaced.

The post ATI AT6002 Multi-Channel Power Amplifier Review appeared first on HomeTheaterHifi.com.

Emotiva XPA-1 Gen 2 Monoblock Power Amplifier Review Highlights

Emotiva made their name by producing high power, affordable amplifiers.

Perhaps no amplifier personified that more than the XPA-1. The original XPA-1 offered 500 watts into 8 ohms and 1,000 watts into 4 ohms. The updated model improves on this by delivering 600 watts into 8 ohms and 1,000 watts into 4 ohms. It also offers a Class A mode accessible by a switch on the front panel. When engaged, this provides 60 watts of Class A, but retains the ability to provide up to 600 watts in Class A/B mode.

Emotiva XPA-1 Gen 2 Monoblock Power Amplifier Highlights Summary

• 600 watts into 8 ohms, 1,000 watts into 4 ohms
• Switchable Class A and A/B modes
• Balanced and Unbalanced Connections
• Oddly spaced binding posts
• No handles or rack mounts provided

Introduction to the Emotiva XPA-1 Gen 2 Monoblock Amplifier Review

Emotiva made their name by producing highpower, affordable amplifiers. Perhaps no amplifier personified that more than the original XPA-1.

The original XPA-1offered 500 watts into 8 ohms and 1,000 watts into 4 ohms. The updated model outdoes this by offering 600 watts into 8 ohms and 1,000 watts into 8 ohms. It also has a Class A mode, accessible by a switch on the front panel. When engaged, this provides 60 watts of Class A, but retains the ability to provide up to 600 watts in Class A/B mode.

The XPA-1 Gen 2 is the most powerful Class A/B amplifier that Emotiva makes. We know it has raw power, but does it also have grace and finesse to go along with brute force?

Design and Setup of the Emotiva XPA-1 Gen 2 Monoblock Power Amplifier

The XPA-1 is a balanced, discrete Class A/B monoblock amplifier. It features XLR and RCA inputs on the rear, with a switch to toggle between the two inputs. 12V triggers have a 3.5mm input and output, so you can chain two XPA-1s together if you wish. The front has the switch to move between Class A and Class A/B modes, along with an LED meter showing the relative output level. If you find the LEDs too bright for your room, you can disable them on the rear panel. There are optional rack rails available, though they are not included in the box.

Despite being a monoblock amplifier, there are two pairs of binding posts on the rear of the XPA-1. This allows you to bi-wire speakers with two individual runs of cables if you desire.

I felt that the binding posts are too far apart. Over a foot separates the positive and negative terminals, and most speaker cables will likely not reach them by default. I added a banana extension for my cables to enable them to make it, but you might need to split your speaker cable at the end so that the two legs can reach each set of binding posts.

The biggest internal change to the XPA-1 Gen 2 is the addition of the Class A switch. When you enable this, the first 60 watts from the amplifier are Class A. If you need more power, you can switch it to Class A/B operation. If you have the switch in the Class A/B mode, it operates there all the time. Since both modes have access to all 600 watts, why wouldn’t you leave it in Class A all the time?

The answer is simple: heat. Class A means that the amplifier is always drawing power and Class A amps are only 25% efficient by nature. With 60 watts of Class A power, that means 180 watts of power are dissipated as heat when the amp is idle. Leaving the XPA-1in Class A mode at idle for an hour bears this out, as the amps will become quite warm.

One other feature I would like to see on the XPA-1 Gen 2 would be rack handles. While not the heaviest amplifiers I’ve moved around, they are the heaviest without handles.

The Emotiva XPA-1s were set up in my system using a Marantz AV7005 preamp, an Auralic Vega DAC, or an Anthem MRX510 receiver. The Marantz and Anthem connect with RCA, while the Auralic uses XLR connections. The speakers are Revel f208s, which have a nominal impedance of 8 ohms, but dips down below 4 ohms at various points.

The Emotiva XPA-1 Gen 2 Monoblock Power Amplifier In Use

In Class A/B mode, only a few of the LEDs on the front of the XPA-1s lit up, because the speakers ae sensitive. A single LED or two was as often as much activity as I got with some music. Throwing on some Led Zeppelin re-issues changed that, and I was treated to a light show, as the LEDs danced back and forth. Driving the f208s in full range, the XPA-1s had no trouble keeping up with John Bohnam’s insane drumming.

Even more aggressive than Zeppelin is Reckoner from Radiohead. It explodes out of the speakers from the first note. The song is crisp and dynamic, with no strain from the f208s at all. Even pushed to the limits for my volume tolerances, the XPA-1s didn’t go beyond 2/3^rd on their LED meters. The XPA-1s have plenty of headroom, even if you have more demanding speakers than the Revels.

Movies also come to life with the XPA-1s. The opening attack scene from Pacific Rim startled me in my chair as the roar of a Kaiju attacking San Francisco filled the room. Another piece of eye and ear candy (with no plot) is Transformers: Dark Side of the Moon. With massive explosions and battles that I pushed through the Emotiva pair, they never hiccuped.

Listening in Class A instead of Class A/B, I admit I did not hear a difference in the sound quality, perhaps because Class A/B mode sounded so good.

However, I did notice two distinct things in Class A mode compared to Class A/B mode. The first is the heat. When both amps were on a rack behind my seating area, I could feel the warmth it gave off after an hour or two. When I moved them to the front of my room to make the A-A/B switch easier to access, I didn’t notice the heat until I got up to turn them off.

The second is a metallic popping sound that the amps would give off in Class A mode. It sounded different than a relay click, and was never audible in Class A/B mode. Since it happened during music playback, where I could hear it, and also after turning them off, I imagine it is a thermal issue. Perhaps the case screws were expanding or contracting and causing the sound.

In both Class A and A/B modes I could also hear a slight hiss from the tweeter. It was very low level, and I had to be close to the speaker, but it was there. It was low enough that I couldn’t hear it in use unless the music was in between tracks.

The Emotiva XPA-1 Gen 2 Monoblock Power Amplifier On The Bench

David A Rich Ph. D. and Chris Heinonen

All AC wattage measurements are in units of Watts average, not RMS.The Emotiva adds a Class A biasing option to remove crossover distortion. The amp transitions to Class B at 60 Watts into 8 Ohms and 30 Watts into 4 Ohms.

The power amp gets hot in Class A mode, reading 110 F on the amp surface and 120 F inside the chassis (using a thermal IR gun) after 20 minutes . In Class A/B mode it only rose by 5-10 degrees.

The XPA-1 design causes the performance in mode Class A/B mode not to be optimized. This is the result of including the Class A biasing option. It is possible to have both Class A and Class A/B optimized, but this requires extra circuitry not in the XPA-1. Details are in the section below called Design Technology in the Emotiva XPA-1.

Power Output of the Emotiva XPA-1 in Class A and Class A/B Modes into an 8 Ohm Load

We tested with the unit into a standard AC line with no VARIAC (a high current rheostat that allows you to keep the AC supply at 120 volts), which may have resulted in higher distortion levels.

Test at 630 Watts into 8 Ohms (Emotiva spec limit)

In Class A/B mode, THD was 0.11 % and the 19kHz / 20kHz IM test result was 0.05 % (average of the IM levels of the first 3 IM products at 1kHz, 18kHz and 19kHz).

In Class A mode, THD was 0.17 %, and the 19kHz / 20kHz IM test measured 0.05 %

Test at 1,030 Watts into 4 Ohms (Emotiva spec limit).

In Class A/B mode, THD measured 0.1%, and the 19kHz / 20kHz IM measured 0.13 %

In Class A mode the THD measured 0.13 % and the 19kHz / 20kHz IM test measured 0.11 %

Distortion Spectra A/B modes 600 Watts into 8 Ohms

The spectra below is of the amplifier producing 600 Watts (69.2VRMS) in Class A/B mode.

The THD was 0.004%. Note the odd harmonics are significantly larger than the even harmonics as expected for a balanced amplifier The 19kHz / 20kHz IM was 0.0028%

Give the importance of the distortion structure in a balanced amplifier, I have listed the harmonics below. The 3^rd harmonic is predominate, with the 2^nd the only other significant harmonic.

Below is a plot under the same conditions from 0Hz to 1kHz.

The hum was well suppressed, with the maximum spur at -110dB. This is again expected in a balanced amplifier with continuous current flow in both supply rails and no current flow in ground.

At 600 Watts into 8 Ohms, the 19kHz / 20kHz IM was 0.0028% for the first 3 IM products (the IM products were at 1kHz -115.20dB, at 18kHz -96.50dB and -97.78 at 21kHz).

Signal to Noise (S/N SNR) Measurements in Class A and Class A/B

The measured noise of the XPA-1 was higher than the majority of other high quality amplifiers. The reason for this is explained in the Design technology in the Emotiva XPA-1 section below.

The measured noise at the output was 120 µVRMS with the input grounded, over a bandwidth of 20Hz to 20kHz. Using the measured noise, the SNR can be calculated for different output references values. The full power SNR runs are direct measurements.

Class A/B

78.4dB ref 1VRMS

87.4dB ref 1 Watts into 8 Ohms (2.8VRMS).

115.4 dB ref 630 Watts into 8 Ohms (71.1VRMS)

114.6dB ref 1,030 Watts into 4 Ohms (64.2VRMS)

The amplifier’s heat in Class A results in higher noise because of the nature of electronic circuits and temperature (electronic noise). We measured the noise of the amplifier at its output at 142µV RMS with the input grounded. This is 1.4dB higher, so the SNR is 1.4dB lower.

Class A

77.0dB ref 1VRMS

86.0dB ref 1 Watt 8 Ohms (2.8VRMS).

113.8 dB ref 630 Watts into 8 Ohm (71.1RMS)

113.2 dB ref 1,030 Watts into 4 Ohms (64.2VRMS)

The Emotiva XPA-1 has a gain of 30dB (31.55V/V) at 1kHz, although this changes slightly when the amplifier is driven to 1% distortion.

Comparison in Performance Between Class A and Class A/B

Below is a comparion of the spectra of the amplifer in Class A and Class A/B mode outputting at 12.5 Watts into 8 Ohm (10VRMS). The distortion rises at higher power but a problem with the swept data curves prevents showing this here. We also cannot show when the Class A and Class A/B distortion curves merge.

XPA-1 8 Ohm Class A Data 12.5Watts

XPA-1 8 Ohm Class A/B Data 12.5Watts

For Class A mode, THD was 0.009% and the 19kHz / 20kHz IM was 0.0069%

For Class A/B mode, THD was 0.0022%, but the 19kHz / 20kHz IM was similar at 0.0071%.

A comparison of the individual spur values provides insight of the performance in Class A and Class AB. The first line is Class A mode of operation.

Below is the spectrum of each spur.

Strangely, for Class A/B the 2^nd harmonic dominates, indicating it must be at a high level single-ended. This was also the case for 5 Watts. This is an indication that the Class A/B is not optimized. Nevertheless, the spur is low at 0.0022% at 10 Watts output.

At 600 Watts output, the Class A/B spectra above the 2^nd harmonic is actually lower in level. The 3^rd harmonic dominates the 600 Watt measurement at 88dB down.

For Class A, at 12.5 Watts output, the 3^rd harmonic dominates as expected for a Class A amplifier. The 3^rd is the only harmonic that can be said to be significant.

The 19kHz/20kHz IM test at 12.5 Watts into 8 Ohms does not show significant differences between Class A and Class A/B.

For 5 Watts in Class A operation, THD was 0.0005%, and the 19k/20K IM was 0.0032%

In Class A/B operation, THD was 0.002% and the 19k/20K IM was 0.0037%

The 1kHz spread between Class A and Class A/B is now 1 to 4, but these are low in level.

4 Ohm Performance at Lower Output Levels

In Class A mode, THD was low at 0.0009% at 5 Watts. It increased to 0.002% at 35 Watts.

In Class A/B, THD was at 0.0045% from 5 Watts to 60 Watts.

Problems with the swept measurements prevent filling the data at higher power levels.

The spectra for the amplifier driving 25 Watts into 4 ohms A/B mode is shown below.

The 2^nd harmonic is the dominant distortion at 0.004%. The 19k/20kHz IM was 0.009% for the first 3 IM products.

Design technology in the Emotiva XPA-1

David A. Rich Ph. D.

Emotiva supplied a complete schematic. I thank them for the openness they provided on the design. This section assumes the reader is familiar with the introductory presentation on balanced amplifiers: The Fully Balanced Power Amplifier – Advantages and Design Challenges

Please refer to this article directly for a discussion on the sub-optimal Class A/B bias circuit mentioned in the measurement section above.

The XPA-1 topology is based on a single voltage gain stage. Almost all power amplifiers have two stages of voltage gain. A single stage of voltage gain is easier to stabilize. That is important in a fully balanced amplifier with 3 feedback loops.

With only one voltage gain stage, the open loop gain of the amplifier is attenuated, and this reduces the return loops gain of the feedback.

With less loop gain, the amplifier is less able to reduce distortion by the use of negative feedback. Emotiva uses other design approaches to improve the open loop distortion of the XPA-1 amplifier. This includes the fully balanced amplifier design to cancel even ordered distortion as discussed in the introductory piece. A fully complementary design is also used as is the Class A output stage up to 60 Watts (30 Watts into 4 Ohms).

The circuit topology of the Emotiva XPA-1 is close to Figure 2 of the document below which is a differential opamp.

Karki, J. “Fully-Differential Amplifiers.” Texas Instruments, Application Report SLOA054D, 202, p. 4

http://www.ti.com/lit/an/sloa054d/sloa054d.pdf

Copyright restriction prevents me from showing the schematic here.

The gain of a voltage gain stage can be increased by increasing the stage’s output resistance. One way to do this is to use a technique call the folded cascode. Explaining this technique is beyond the scope of this review. The folded cascode can be seen in Figure 2 of the reference noted above. Since only one voltage gain stage is used in the XPA-1, techniques to raise its gain are mandatory.

In the Emotiva XPA-1, the voltage amplifier is on regulated ± 64V rails to isolate the stage from the power supplies noise on the unity gain current amplifier sourcing and sinking current to the pair of output stages. The designer must take great care to sequence the turn-on times of the multiple power supplies to prevent fault conditions.

The output stages are on unregulated ± 52V rails. This allows each single ended stage to swing approximately 35VRMS. In balanced mode, that is 70VRMS. Into 8 Ohms, this is 612 Watts average. In practice the amp produced 71VRMS before starting to clip.

In the Emotiva XPA-1 every PNP transistor is matched by an NPN transistor for the entire circuit, so the voltage gain stage is also complementary to reduce distortion. To accomplish this, one additional differential pair with PNP input devices is added to the schematic in Figure 2 of the paper by Karki.

The common mode feedback circuit shown in Figure 2 of the Karki paper is not the same as the Emotiva XPA-1. We will discuss the circuit Emotiva uses in the next section.

The current gain stage connected to the speaker is an emitter follower triple. Six transistors in parallel are used in the final stage of the triple. Since this is a balanced and complementary map, 24 transistors are connected to the speaker.

With the single voltage gain stage, it is important that the input of the current gain amplifier has a high resistance at its input. The gain of the voltage gain stage is directly dependent on the loads it sees.

Common Mode Feedback

The fully complementary topology allows Emotiva to make the common mode feedback very simple in the XPA-1. Emotiva observes that as both speaker terminals move away from ground, producing a common mode error, each of the complementary differential pair tails also moves

The amplifier senses the movement of the differential pair tails. If the speaker terminals drift in the positive direction followed by the differential pair tails, more current is forced into the NPN-based differential pair, pulling the speaker terminal back down

If the speaker terminals drift in the negative direction, more current is forced into the PNP-based differential pair, pulling it back up.

The common mode feedback loop degenerates to being just resistive in the actual design, instead of the standard common mode feedback circuit that uses an additional internal op-amp (Figure 2 of the Karki paper).

How Emotiva designed such a simple circuit that works so well is kept proprietary. The very simple common mode feedback circuit makes stabilization of the common mode feedback easier.

Compressive Fault Protection

The Emotiva XPA-1 has a relay in the speaker line to prevent any fault condition from damaging the amp or the speaker. If the fault condition is a shorted transistor, the relay will prevent the short form being seen by the speaker. The unit has a special chip common to modern amplifiers (uPC1237) that monitors for excess current draw of the output transistors (perhaps an external short circuit or a defective transistor which will require service) and DC offset at the speaker terminal output. Disconnection of the power supply on over-temperature is done with a different circuit.

The IC (Integrated Circuit) times when the relay closes at power-up and opens at power-down. It will keep the relay closed until it is sure a fault condition exists, and the amp will not open the relay when the amp is driving a difficult speaker load.

The fault condition status is coordinated by a micro-controller. Some faults are displayed on the front panel.

The unit has a standby power mode also controlled with relays.

SNR levels lower than expected

Amplifier noise was discussed in: The Fully Balanced Power Amplifier – Advantages and Design Challenges

The measured noise at the output was 120 µVRMS over a bandwidth of 20kHz with the input grounded. The Emotiva XPA-1 has a gain of 31.5V, so the input referred noise is 3.8µVRMS.

This is an inverting topology, which can have the noise floor dominated by the input resistors thermal noise.

The balanced input has a 20kOhm resistance. At 800 F, the thermal noise is 2.6µVRMS. I found this value using an on-line thermal calculator.

http://www.sengpielaudio.com/calculator-noise.htm

The excess noise beyond the thermal component is mostly the enhancement from base current noise, although the amplifier has other components that produce noise and could add to the total.

When the amplifier is switched to class A the SNR was found to decline by 1.4dB. The internal temperature increased by more than 400 F and resultant increase in thermal noise accounts for some of the decline in SNR.

The SNR can be improved if the 20kOhm input impedance is dropped to 200Ohms. The input would then be driven by a buffer that would present a light load to the preamplifier. Indeed, the buffer is in place for the single-ended to balanced converter, although the op-amps in place cannot drive 200Ohms. The circuit would be discrete or an op-amp – discrete composite. The buffers must be single ended for reasons outlined in the introductory article.

Conclusions about the Emotiva XPA-1 Gen 2 Monoblock Power Amplifier

Emotiva made their name with big, beefy amps, and the XPA-1 Gen 2 continues that tradition. Building upon the original with a Class A mode, it has lots of power in reserve. When it comes to pure wattage value, the XPA-1 is a tough beast to top. Running a full range tower speaker, the Revel f208, I never came close to maxing out the XPA-1s’ reserves. Even those with large planar speakers should not worry about running out of juice here.

The only ergonmic faults I have with the XPA-1 are the placement of the speaker binding posts so far apart, and the lack of handles to move them (they are really heavy).

With performance I find little to disagree with on the XPA-1 Gen 2. If you have power hungry speakers, or you just want to be certain you have plenty of headroom when you play orchestral pieces with pipe organ, this power amplifier will do the job.

The post Emotiva XPA-1 Gen 2 Monoblock Power Amplifier Review appeared first on HomeTheaterHifi.com.

However since it retails for $4000 without a phono stage ($5500 with), and the base ET3 line stage goes for only $2950 on Amazon with free shipping, I thought a review of the 25%-off base version might be appropriate.

Conrad-Johnson has a storied reputation for building some of the finest-sounding preamplifiers in the world. Their philosophy of “use the absolute minimum number of the highest-quality parts” is on display in the ET3.

A pair of PhD economists who are also world-class practitioners of audio design run the conrad-johnson company. The lower case leading letters are intentional. Since the 1970’s, Drs. William Conrad and Lewis Johnson have designed and produced a series of audio electronics (mostly preamplifiers and power amplifiers) that have consistently received the highest audio reviewer rankings.

The conrad-johnson design company is located in Fairfax, Virginia. After decades in business, the company is still sound, still innovative and still produces a uniformly high-quality line of products.

Unlike most brands, don’t expect to buy a conrad-johnson (CJ) product and then have a newer version suddenly make your purchase obsolete. Most CJ products tend to remain in production for years. This longevity is not an indication of sloth on the part of the designers, but is, rather, due to the fact that until better technology is available, CJ doesn’t believe in constantly upgrading or tweaking their gear.

CJ has a design philosophy of “less is more.” They’ve been quoted as saying that a design is finished when no more parts can be removed. By minimizing the parts-count, more of the design budget is available to optimize the quality of the remaining components.

The ET3 is also fitted with a resistor-ladder, relay-switched volume control. Such a control costs significantly more than the variable-resistance wiper controls found on most preamplifiers (even the most expensive ones), but results in more consistent channel-to-channel balance throughout the entire volume range.

Attention to detail is also present in the smaller things. The gold-plated input and output jacks are of very high quality, and the vacuum tube (a single, dual-triode 6922) is fitted with a pair of flexible ring-dampeners to suppress tube microphonics.

The factory tube is a Russian-made Electro-Harmonics, and since there is but one, inexpensive tube-rolling is possible. Normally when two tubes are present, one must purchase matched pairs in order to maintain channel-to-channel balance. The added cost prices many owners out of the tweaking experience. With the ET3 a single tube is sufficient, and the expense of buying gain-matched pairs is unnecessary. It is also far more probable that the two internal plates of a single tube are going to be exactly matched and will age at the same rate.

Even the front panel is finely finished with beveled buttons and a clean look.

The ET3 was used to replace a McIntosh C220 tube preamp, which replaced an Emotiva (solid-state) XSP-1 Gen 2 preamp. My associated equipment included:

• JRiver Media Center 21 for Mac playing WAV files from a USB-RAID-HDD
• Oppo BDP-105 (used as disc player & DLNA-connected DAC)
• Emotiva XPA-2 Gen 2 solid-state power amplifier
• Axiom M-100 loudspeakers
• PowerSound Audio XV-15se subwoofers (2)

The RCA interconnect cables were somewhat difficult to plug into the ET3 due to the high force required for inserting them into their sockets. I ended up having to hold the front of the (light weight) preamplifier with one hand while pressing the plugs into the back. I have no complaint about this, but do note it in passing.

I’d also comment here about CJ’s attitude toward balanced circuitry. Although they concede that XLR cables and balanced circuitry have their place in commercial audio, they contend that for home audio, balanced circuitry is “a solution in search of a problem.” This is fully in keeping with the CJ proclivity for simple circuitry.

The CJ has a unique sound that isn’t much like anything else I’ve heard, except maybe from the Wadia brand of DACs. It’s very interesting how different my Axiom speakers can sound when the CJ is in the system. The sound wasn’t like that of the McIntosh C220 tube preamp, nor did it sound like my former Emotiva XSP-1. The ET3 had its own unique presentation.

If you like Pink Floyd, Van Halen, Kool-Moe-Dee, or anything else with deliciously funky electric guitars, this is the preamp for you. A capsule description of the sound would be “lit up from the inside.” Mr. de Silva felt that the CJ had a similar sound to that of class-A, solid-state power amplifiers, but with a lot more tube magic going on, of course. In short, this is a preamp you can crank.

The CJ did a bit better than both the Mac and the XSP-1 with lower bass that provided more impact, more slam and more room pressurization. The Mac and the Emotiva preamp have more neutral bass sounds. The McIntosh in particular has a nice laid-back air with a very natural in-room feel. The CJ said, “Laid-back? I’ve never heard that term!” and proceeded to give you so much rocking goodness it made your head spin. I don’t think my toes ever stopped tapping; I was drumming out tunes in the air!

The “lit from within” perspective could be varied to some extent with different brands of tubes. A variety were tried including the factory Electro-Harmonix, a Genelex Gold Lion premium and a Telefunken. The Genelex tube was the liveliest with the Electro-Harmonix in the middle and the Telefunken the most laid-back. But even with the latter installed the sound was still livelier than either of the other two preamplifiers.

Playing rock music, it’s hard to describe how intoxicating the ET3 is. If the preamp could speak for itself it might say, “Bring back the ’70s and all its delicious grooving, but with exceptional resolution and high fidelity.” Make no mistake – this preamp can rock! It really enhances pop music. I can’t think of another preamplifier that I’ve auditioned that jams like this.

The McIntosh is more about intimate jazz, a smoky bar room, Holly Cole caressing your ears, and an organic, natural presentation. The Emotiva XSP-1 is Sergeant Joe Friday (“just the facts, ma’am”). But in the CJ’s case, somebody turned on the nicest tube guitar amp you’ve heard and voilà! – The Grateful Dead perform right in front of you. Neither of the other preamplifiers had this degree of presence.

Drums sounded quite good as well. You can easily discern all the different and delicate things the drummer is doing. Also the midrange whack of the drumheads, particularly on the toms, comes through with lots of power. The temptation is to keep turning the volume up because it sounds so good – so much that the clipping level of the power amplifier is easily approached.

But I never noticed it before until the ET3 called attention to it. And there is a lot of detail in that cymbal shimmer. Mr. de Silva asked to stop this song that we’ve both listened to many, many times and said…”wait – did you hear that cymbal?”

From the same album, we listened to the track, Lonestar. During this song there is an acoustic slide guitar performed by Mr. Adam Levy. As he plays the notes, he shakes the slide to add a secondary percussive sound on top. It’s very subtle and not every piece of gear can bring it to life but the CJ was up to the task!

That being said, the treble emphasis that is so pleasant on some music can be a bit too much in other cases. Orchestral cymbals sometimes take on a life of their own and stand out too much. When I attend a symphony concert, I’m accustomed to certain percussive treble sounds that float over the orchestra; typically cymbals and triangles. But the CJ overemphasizes this frequency range. If your system is also bright, this alone may be a deal breaker.

In the midrange, horns sound like the contrast is turned slightly up (mostly in a good way) and jump out at you, demanding your attention. The downside of this is that Norah Jones’ voice became less natural. When the vocal comes in, the contrast is too great. It sounds like she’s coming out of the soundstage to sing directly into your ear, and with a bright, harsh edge. But there were several other songs where the effect was quite pleasant.

We often buy a high-resolution stereo system and suddenly find that all the songs we really liked on the radio no longer sound so good. Instead, we start listening to well-recorded fare that nobody would otherwise listen to because it’s the stuff that sounds good on the system. Eventually, Led Zeppelin, Reverend Horton Heat and Dash Rip Rock fall off the playlist for good. And I miss that – I miss the fun tunes.

And you know what? He didn’t either! It just wasn’t enjoyable on his system. You couldn’t crank it much. But on the CJ, we listened to the entire song cranked up to near clipping, and it sounded so good; that’s what this preamp can do.

Using the ET3 with a more laid-back vacuum-tube power amplifier would probably balance out the treble better. Unfortunately I didn’t have one on hand to audition. But I’d say that if you have a neutral solid-state power amplifier and neutral speakers, the treble emphasis and the midrange dynamics of the ET3 might not be your cup of tea. Even worse, if you have older solid-state amplification, that tends to be brighter in the treble, or if you have a pair of speakers that also emphasize the treble region, then the ET3 is definitely not for you.

But it’s also fair to say that the Telefunken tube did away with about 50% of the treble emphasis while also opening the sound stage significantly and maintaining the ET3’s signature sound.

Since I lack acoustic or electrical test equipment, I can’t verify the ET3’s frequency range against CJ’s specs. I do note however that CJ specifically doesn’t specify a frequency response variance (plus or minus how many decibels) over the preamp’s total frequency range. Even if the frequency response does measure ruler flat, the perceived treble emphasis is a consistent artifact of the preamplifier’s sound.

At the time of this audition, I had two power amplifiers available. One was an Emotiva XPA-5 Gen 2 and the other an Emotiva XPA-2 Gen 2. Of the two, my speakers seem to prefer the power reserves of the two-channel amplifier so I used the XPA-2 throughout the auditioning of the ET3 preamp. It has sufficient current to bring out the best of the four-Ohm Axiom M100s at higher volumes yet maintains dynamics and tone when playing at much softer levels.

A number of comparably priced preamplifiers are available, with or without tubes. In the $3000-and-under range, credible contenders would include the Rogue Audio Perseus, Odyssey Audio Tempest SLB, Audio by Van Alstine FET valve CF, PrimaLuna Dialogue 3, Parasound HALO P7, Vincent Audio SA-T7 and an infinite variety of used preamplifiers. Although I’ve heard many of these, I haven’t spent enough time with them to provide an accurate comparison.

Suffice it to say that the CJ ET3 is quirky enough with its treble emphasis and dynamic midrange that it will probably resist direct comparisons with any competitor. You’ll either love the CJ sound immediately, or you won’t. The ET3 is, more than any other preamp I’ve heard, one that you should listen to carefully before you buy.

I Can’t Say That the conrad-johnson ET3 Is a Neutral Component. Its Unique Sound Signature is Audible on Every Recording.

I can’t say that the ET3 is a neutral component. Its unique sound signature is audible on every recording. So if you’re one for whom fidelity to the original recording is paramount, you’ll not likely find this preamp to your taste.

I’m a bit surprised at the ET3. The special edition version of this preamp is on most everyone’s recommended-component list. But given the treble emphasis and midrange dynamic exaggerations that the base ET3 model exhibits, I wouldn’t necessarily consider this model a high-end contender. Since I haven’t heard the SE version, it may be significantly more neutral than the base model.

This is not to say that the preamp doesn’t have its charm – only that it isn’t sufficiently neutral to have a long-term place in my system.

If, however, you are looking for a high-resolution, fun-sounding take on music, and rock music in particular, then the ET3 provides it in spades. You’ll be listening more loudly to all your music just because it just sounds so good.

– Glenn Young & Garuka de Silva

The post conrad-johnson ET3 Tube Stereo Preamplifier Review appeared first on HomeTheaterHifi.com.

A complete audio manager, the Halo Integrated offers analog and digital inputs and a robust amplifier section.

Back in 2014, I concluded in my review of the Parasound Halo P-5 preamplifier saying that it was simply a bargain because it included in addition to the preamplifier, a DAC, bass-management, a phono stage and headphone jack. The only thing possibly missing was amplification. Well now that’s been done! And it wasn’t much of a stretch to add as Parasound makes some great power amplifiers, we just needed Richard Schram, President and Founder, to build it. Is the Halo Integrated simply a P-5 with an amplifier!? Well, yes, sort of…but it’s not surprising that Parasound made it more.

The Integrated hasn’t varied much styling-wise from the current Halo line. The description of the Integrated can read like any other Halo product; slightly sloped brushed aluminum faceplate and softer rounded ends. The edges are still glossy grey plastic matching the brushed aluminum. What is most noticeable is the etched logo which differs from the typical Halo product that is silk screened. The illusion is the face-plate has more depth or heft. I assume this will be the new format for the logo moving forward on Halo products.

Adding the amplification I’d expect the case to be larger and naturally heavier than the P-5 and so the Integrated stands a shade less than 6” and weighs 33 pounds receiving most of its heft from an oversized toroid power transformer with 40,000 µF filter capacity.

In keeping with the audiophile “look” there is no visible display of any kind and the Halo Integrated front is arranged simply and cleanly. Parasound makes use of LED backlighting to emphasize selector buttons. The glowing buttons are the power on/off and the mute, both switching from blue to red when activated. The smaller tone control also glows when active. Most importantly as I discovered the volume control also glows with a clock-hand stripe indicating the volume level. I do listen to music mostly in the evenings and generally in darker rooms, having the volume visible made my life a lot easier.

But the layout is straightforward input selection is indicated along the bottom, a large volume control on the upper right and smaller buttons for balance and sub level. Additionally there are two front face jacks, one for headphones and the other for auxiliary use. The Aux input is given a 12 dB gain matching volume levels of other sources.

The rear layout again is classically Halo; inputs include RCA, line-level analog for up to five devices, a sixth MC or MM phono input with selectable cartridge gain and not least a balanced XLR input.

A 384kHz ESS® Sabre32 Reference DAC handles the three digital inputs and include; asynchronous USB 2.0 supporting PCM up to 384 kHz/32-bit, native DSD 256 and also DoP DSD streams and the coaxial and optical inputs support PCM up to 192 kHz/24-bit.

Balanced outputs for both channels also include a third XLR output for a subwoofer. Speaking of bass…

The Halo Integrated “2.1” identifies analog bass management for your subwoofer. By switching off the crossover on your subwoofer, both low and high pass crossover settings on the Integrated can be set from 20-140 Hz. Final volume adjustments can then be made on the front panel. You can also deactivate the Parasound crossover and send a full frequency signal for the subwoofer to handle the crossover settings.

Like all Parasound Halo preamplifiers, the Integrated allows for a theater bypass if the unit is placed in a system beyond two-channels. This feature allows you to use the Halo Integrated for the front two speakers while letting your processor/receiver handle the remaining channels. Additionally, the Integrated can be controlled with IR inputs from third party sources. The Halo also includes a 12-volt trigger for on/off options including an amplifier fitted with a 12v input.

The Integrated shares with all the Halo amplifiers a Class A/AB, J-FET input stage and MOSFET driver stage. Integrating the amplifier with the pre-amp sections, Parasound made great efforts to isolate the power supply, intended to remove cross contamination. 160 WPC driving 8 Ω speakers is the least you will achieve. I can tell you it’s more than plenty but if you insist on using the Integrated as a preamp only, Halo provides a pre-amp output with crossover settings.

A word about the Halo manual, it’s very well done and not only gives instructions but also good advice, just like Richard Schram would do.

The beauty of this integrated amplifier is truly the single-source management – bringing together every possible input I have. The turntable I use is the Marantz TT 15S1. Additionally I fed the Halo Integrated an analog input from a Meridian Explorer 2 DAC using my MacBook Pro and Audirvana Plus software playing MQA material. I’m in the process of auditioning the newer version of the Meridian Explorer DAC previously reviewed. I also fed high-resolution audio material direct from my MacBook to listen to the Halo internal DAC and used a Marantz SA 15S2 SACD player as a transport letting the Halo do the digital processing.

For speakers I used PSB full-range Imagine X1T and their SubSeries 200 subwoofer. I did spend a fair amount of time with the subwoofer crossover settings on the rear getting what I thought was just the right balance. I took my time trying both the crossover options on the Integrated as well as defeating it and letting the sub control the crossover settings. In the end I enjoyed using the Parasound bass management because it allowed me to make some final adjustments on the front panel.

All cables used were from Transparent Audio, speaker, interconnects, USB and power.

Anyone familiar with Parasound’s Halo “sound” will know how neutral their amplifiers and pre-amps are, leaving no signature of their own, whatsoever. This was consistent, of course, with the Halo Integrated. The least concern I had was the power output, I rarely turned the volume dial much past 10 o’clock where the dynamics reached a pinnacle volume with no distortion or clipping. Likewise, low volume playback didn’t degrade the sound or leave it flat. I would also say that this contributes to a very flat frequency response, across the board.

I managed to break-in the Halo Integrated feeding it a digital signal from my cable box until I was able to install in my two-channel system. The Halo Integrated did run a bit warm although I wasn’t overly concerned about it. What also struck me was how quiet the Halo amplifier is. Other than a bit of feedback from my turntable there was virtually no hum or hiss from my speakers.

In my experience, Parasound Halo amplifiers always offer a spacious and open soundstage with excellent imaging from vocals and instruments. Bass as adjusted is simply pleasurable – palpable, convincing, deep and tight.

Using my CD player as a transport, I ran a digital signal to the Integrated via Toslink. Bruce Cockburn’s Speechless Instrumental guitar-centric music was impressively rich and textured with an abundance of depth and dimension. The low bass strings had enough weight while the upper notes were airy and clean.

Cantus, While you Were Alive CD is beautiful choral music, a bit eclectic yet offers a wonderful spacious sound. The Halo Integrated renders the nine male voices with depth and character. Powerful and gentle, their voices are articulated, sensing the deep bass and baritones to the high countertenors in the group.

The Beatle’s White Album on vinyl offers not only the voices of the Beatles but some wonderful orchestration as well. The Halo played several tracks to a level I truly never appreciated before; instruments especially were well defined articulate while there was significant clean bass impact. In fact it made me make the slightest adjustment to the front bass control.

The Halo also impressed me giving the Miles Davis’ 1956 album, Relaxin’ With The Miles Davis Quintet studio recorded album a club “feel”. Melodic, with excellent instrumental tone and spatiality, Miles’ trumpet always front and center sounded clean, articulate and brassy. The piano was sufficiently mellow and warm while standup bass was rich and full.

The Halo doesn’t shy away from some extra volume as I cranked some digital high-resolution music via my laptop, listening for that “cold” digital sound. What I got in truth from the Halo was a new appreciation and respect for high-resolution audio because it sounded much richer and more textural than I’ve heard in the past, at least in my system. For lack of a better word, there is truthfulness to the sound of the Halo Integrated. I downloaded several pieces of music from HD Tracks, none give me more goose bumps than the 2L MAGNIFICAT track 4: Et misericordia at 352 kHz/24 bit playback. The Halo handled the Nidarosdomens jentekor girl’s choir with such finesse and warmth I’m left in awe.

Additionally impressive from the 2L orchestral music Astrognosia & Aesop also in 352 kHz/24 bit playback, the thwack of the bass drums, the delicate flutes and brass instruments are superb through the Halo Integrated.

Although MQA is the most exciting format going at this time, I am only able to feed MQA material through the Meridian Explorer 2 via a line level input thereby bypassing the DAC in the Halo. Still no less satisfying, the Halo handled the analog input gracefully. DSD64 tracks like Mozart’s Violin Concerto in D major KV 218 or Haydn String Quartet in D, op. 76, No. 5 both offer rich renditions of the string instrument, with proper timbre, speed and authority.

Worthy to note, running the high-res audio through a Mac doesn’t require the setup required for a PC. Windows users will be asked to download drivers.

Lastly I do apologize for not spending time with the headphone section of the Integrated, perhaps if there is enough time before I return the Halo Integrated I will have spent some quality time listening and augment this review in the future.

Don’t Waste Your Time Trying to Compare What THE PARASOUND HALO Can Offer With Another Audio Product With the Features and Ability of this Integrated at the Price Parasound Sells it for.

Am I biased towards Parasound Halo products? Yes, unquestionably, proudly. I own several pieces. Halo gear is reliable, well made and superbly engineered and can’t be beat for value. You’d be hard-pressed to find anyone who doesn’t like the Halo Integrated – the sound, the features, and the pedigree. With an excellent DAC and an amplifier that has enough punch to handle any dynamics one would want. I’m scratching my head wondering what’s lacking.

This integrated will make you reconsider the need for separates, honestly. I’m thrilled to compare my Parasound P-5 Preamp/ A-21 Amplifier combination with the Halo Integrated; it really is that good and an early favorite to receive“Best of” honors in the category.

The post Parasound Halo 2.1 Channel Integrated Amplifier Review appeared first on HomeTheaterHifi.com.

At that point, it transitions into class AB operation like a normal amplifier and keeps going to over 100W per channel before it reaches 1% distortion. As such the 30W power spec is a massive underestimate of what the amplifier is capable of. Even at that 100W per channel level, the clarity, ease, control and smoothness of the Pass amplifier was second to none in my listening room.

Several years ago, I tested Pass Labs new XA30.5 30W stereo class A power amplifier and declared it the best amplifier I had ever tested personally. Since then, Pass Labs has upped their game and released a new revision of their class A and Class AB amplifiers, the .8 series. These new amplifiers are not revolutionary new designs, rather careful evolutions of the previous .5 series. Pass sent me their new “low power” XA30.8 to see how much better things could get.

Most all of the new .8 series amplifiers are bigger and heavier than their predecessors (only the largest of the amps are the same weight, they were already big enough to handle the .8 treatment). The XA30.8 weighs 93 lbs. as compared to the 76 lbs. of the previous model. The heat sinks are significantly larger to allow increased bias current compared to the .5 models. Class A amplifiers dissipate a significant amount of power even at idle. In the case of the XA30.8, the heat sinks have to get rid of 375W of heat the entire time the amplifier is on. The old XA30.8 needed to dissipate only 200W. This shows the bias current has been increased by 40% in the new model. In addition, the case is larger to accommodate an even larger power supply.

There have been several smaller refinements in circuit layout, input impedance and the turn-on circuit, amongst others. The basic specs of the new amp are about the same as the previous model: the amp leaves class A and transitions into class AB at 61 W per channel into 4 ohms. The measured 1% THD point, where most manufacturers define their power output level as the amp begins to clip, is in excess of 100 W per channel, as confirmed by our measurements of the previous version of this amp, the XA30.5, and measurements of this amp. The Pass Labs specifications they publish are exceptionally conservative. They claim 1% distortion at the maximum rated class A output power, but our measurements show the real distortion numbers to be at least 10 times better than this claim.

The main difference with the new amp, with more output devices running at even less of their rated output power, is the region of single ended class A bias. With the previous amp, this region was about the first 1 W of output power. With the new model, this region has been increased, again by increasing the bias current of the single-ended class A constant current source by 40%.

Normally, you’d need to choose between single ended and push-pull in an amp design, but the clever circuit of the XA30.8 allows the amp to operate like a single ended class A amp at low power output levels. Speaking of circuits, this, and all Pass amps, are monuments to old-school analog circuit design. The entire amp is based entirely on bare transistors. There isn’t an integrated circuit to be found anywhere. In fact, other than in the power supply and in the bias regulation circuit, there aren’t even capacitors in the circuit. Nelson Pass has forgotten more than most people will ever know about analog audio circuit design. You can read even more about the Pass amplifier circuit design and the clever trick they do to allow single ended class A operation at low power.

If it turns out you do actually need more power, Pass makes matching class AB amplifiers. In the case of the XA30.8, the class AB counterpart is the X150.8. It is very similar internally, but biased to leave class A at 12W rather than 30W into 8 ohms, but is capable of larger voltage and current swings so it finally runs out of steam at 150W rather than ~100W. It’s just a question of what you’d prefer: more class A power and less maximum output power, or more maximum output power at the expense of less class A power.

The rear panel is very similar to the earlier XA30.5, but has one nice new addition. The large, wingnut style binding posts with built in tightening clutches now can accommodate banana plugs in addition to spades. Nice, sturdy handles help you heave this massive amp into the rack Anything bigger than this (or the similarly sized XA60.8 monoblock) and you’ll need help. The quality of the case, front panel and blue lit meter are as good as it gets, as it should be for an amp priced like this one.

The XA30.8 certainly did not disappoint. As with the previous iteration, the soundstage with my Gallo Reference 3.5 was jaw dropping. And this was with an improvement in my reference amp since the last test. I had replaced my Emotiva XPA-1s with a NewClear NC1000L amp a while back. The soundstage of the Pass amp was wider, taller and more well defined than the digital amp. And not by a little bit, either. I would estimate 50% more soundstage height and depth, and an increase in width of a foot or so past the speakers on either side.

Of course, this was most obvious on well recorded material with the spatial cues to tell. Two good (and very different) examples were Jon Faddis’ “Rememberances” in 24-96, and the 24-88.2 recording of Daft Punk’s “Random Access Memories.” In both cases, the soundstages were huge. In addition, the size, shape and presence of each image, whether it was Faddis’ flugelhorn or Giorgio Moroder’s voice, were as about as realistic as I’ve ever heard in my room with my system.

Another welcome trait that was preserved from the previous version is the ease and complete lack of glare in the midrange and treble that the XA30.8 delivers. It sounds almost tube-ish in its smoothness and liquidity, but with a complete lack of tonal coloration. For the tube-o-philes among you, give this amp a listen. You might find everything you love about tubes with none of the drawbacks.

Since I didn’t have a XA30.5 around to directly compare, I’m not sure how much better the 30.8 is than the 30.5 in the soundstaging and tonal character department, but I can be pretty sure it’s not any worse. One place where the amp did improve is the bass. It was clear that with the 30.5, there was a bit of an impact with the lower power output. Bass transients were rounded off a bit. I could tell at high listening levels the amp was running out of steam on bass heavy electronica (as I like to listen to) because I could start to see the current meter wagging a bit.

The new higher biased 30.8 has mostly fixed this issue. Bass performance is much better, with transients plenty sharp and impactful. I still could detect a bit of a lack of energy on some albums. Royksopp’s “Melody A.M.” was just a touch less exciting through the Pass amp than with the NC1000L, but that was more than made up for by the improved soundstage, smoothness and detail. This time, I never saw the current meter move, so that says the amp never left class A while I noticed. Still, if I was a rich man, I’d probably go for the XA60.8 monoblocks, which I bet would give me back that little bit of excitement I missed with the XA30.8. With my speakers, anything more would be useless. In any case, I can’t afford either the $6,800 XA30.8 or the $12,800 a pair XA60.8s. But if I could, I would buy them.

Measurements were performed with a M-Audio Profire 610 Firewire sound interface and Spectra Plus FFT analysis software. The XA30.8 was measured using an 8 ohm 300W power resistor as the load. I measured at 1W, 15W and 30W into the 8 ohm load. I was unable to measure the 1% THD power level this time because my new sound card’s inputs reach their maximum input level before the Pass amp does. In fact, testing the XA30.5 a few years ago, I blew up my old sound interface and had to get this new one. As an aside, I had to measure the output of the amp with the positive terminal of the sound interface on one of the amplifier’s outputs and the negative attached to chassis ground, since my sound interface is not floating. The XA30.8 is a differential amp, so the negative terminal of the amp cannot be connected to ground. This means I am giving up some of the distortion cancellation from the balanced output stages when making the measurements, so the measurements presented below are pessimistic.

I measured THD+N with a 1 kHz input signal at 1W, 15W and 30W output power into 8 ohms. As expected the distortion is lower at the lower power levels, but is still an excellent 0.11% even at the maximum power level of 30W. As expected, the frequency spectrum of the distortion is biased towards low order harmonics, another reason why the XA30.8 sounds so good. This is particularly true at 1W power level, where the only distortion products visible are the second harmonic, a little bit of the third and maybe a little of the fourth poking through the noise in the trace. This shows how overbuilt the XA30.8 is and how conservative the 30W output power rating is. The distortion measurements are improved by a factor of a few from the XA30.5 I tested a few years ago. I maxed out my sound card input level at about 50W power level and the XA30.8 was still well below 1% THD, but since I was reaching the sound card’s limit, even some of that distortion was from the sound interface, not the amp. It’s clear the real 1% THD point is well north of 100 W per channel, but I’d need better test equipment to find it. Note that the plots show THD and THD+N. Since I had some 60 Hz pickup I couldn’t get rid of (likely from the trick I needed to do to measure the balanced amp), this polluted the THD+N measurement and made it worse than it actually is.

Intermodulation distortion, measured with 60 Hz + 1 kHz tones was also measured at 1W, 15W and 30W. At 1W, it’s a spectacularly low 0.01%, increasing gradually with power output.

Frequency response is flat as a board as expected all the way to the limit of the sound interface. The small slope you see is the response of the sound interface, not the amp itself. This measurement was done at 15W output power.

The Pass Labs XA30.8 is a very expensive amplifier. It does not have a lot of power output, although it does have a lot more power on tap than the 30 W per channel specification would suggest. But it’s one of the best amplifiers I have ever heard. Certainly the best amplifier I have tested in my listening room. If you have even moderately sensitive speakers, and especially if your system has powered subwoofers, the XA30.8 might just be the perfect amplifier. It has everything you could ever want, with the exception of massive power output. Most people do not need massive power output. If your ego can allow it, this Pass amp could give you world class sound. And I really mean world class in the sense that no amount of money spent could do any better. In my own personal case, I found only one small drawback with the XA30.8 with my speakers and musical taste that would push me to the next larger amp in the Pass lineup. But that comes at almost double the price. I think for a lot of listeners, the XA30.8 could be the holy grail. Yes, it’s expensive. But it’s worth it. If I had the money I would have already placed the order.

$6,800 is a Lot Of Money. But THE XA30.8 is Actually Worth Every Penny of That. Given the Build Quality, Both Inside and Out, The Sound Quality Delivered and the Measured Performance, I Can’t Imagine A Customer Not Thinking They Got Their Money’s Worth. If I Had The Money, I Would Most Definitely Buy a PASS LABS XA30.8 CLASS A AMP.

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At $2495, the Rotel is a new, moderately priced entry in a product category getting crowded with an array of highly-regarded companies like Devialet, Naim, NAD, Peachtree, and Parasound. The Rotel impresses as a thoroughly modern, high-value, high-performance product from one of HiFi’s legendary nameplates.

Back in the early 2000s, Rotel seemed like one of the top go-to manufacturers for budget-minded audiophiles. As I recall, almost every Rotel CD player and power amplifier were fixtures in recommended and best-of lists. Having owned a few Rotel CD players over the years (and compared them to others in their price class), I can attest that such praise was well deserved. Fast forward several years and as I spend most of my time with higher-priced, dedicated integrated amplifiers and DAC separates, it was a welcome change of pace to revisit the house of Rotel. In fact, the timing could not be better because the Rotel’s most obvious competitor, the Halo Integrated from Parasound, was recently reviewed and lavishly praised in these very pages. While a direct comparison to the Parasound would certainly interest me as a prospective buyer, the implicit comparison to more expensive gear I have had over the years convinced me rather quickly that the Rotel offers substantial value for the money.

Rotel claims the RA-1592 “leverages the strengths of [its] award winning RC-1590 preamplifier and RB-1582 Mk II power amplifier in a sleek single chassis design.” The Rotel is a fairly imposing beast by any measure. At first glance, the Rotel’s size makes it look more like a high-end receiver than a stereo integrated amplifier. You soon realize however, that’s for good reason. The array of features makes the Rotel transcend a traditional integrated and more accurately, the Rotel is part of a new generation of fully integrated amplifiers. Yes, I just totally made that up.

As if the size and weight left any doubt, the Rotel does not skimp on power, incorporating 200 watts of Class AB power in a dual-monoblock configuration. If the specifications above haven’t already clued you in, there is a lot going on inside the chassis. In addition to the amplifier and preamplifier, Rotel includes the 32-bit/768kHz DAC from AKM and offers a plethora of inputs, including USB, coaxial, optical, and aptX Bluetooth. Analog inputs include single-ended and balanced as well as a moving magnet phono input. All in all, the Rotel is a very complete package.

The first thing you do is pick a color, black or, like the review sample, silver. The construction itself exudes quality, the metals are nicely finished and there are smooth edges all around. The front corners appear to be solid pieces of contoured, satin-finished aluminum, which provide an interesting variation to the machine-finished front panel. Overall, it’s a classy look. The front panel controls include a dedicated button for each input, a large volume knob, and a dimmable display. While small, the display can be read from a chair, as long it is not too far away. I would prefer a backlit indicator behind the input buttons on the front panel, but since this is also a DAC, I can see why they went with a full display. While it might be easier to read, I would not want the display any larger because the unit would then even more resemble an A/V receiver. For similar reasons, the silver finish might be preferable to black, as nice as I’m sure it may be.

The Rotel arrived on my doorstep in the midst of my binge on the Showtime period drama “Masters of Sex,” which focuses on the complicated relationship between a man and a woman who many regard as the pioneers of modern human sexual research. While it’s very well done and endlessly interesting, it can sometimes feel like being fed Cheesecake Factory size portions of dialogue, which makes it difficult to get through one episode in a single sitting. I watched the show regularly throughout the review period and I really came to admire how clear and focused the dialogue was through the Rotel. I can’t say whether it was the DAC or the amplifier, but the combination, which is the reason why you would buy the Rotel in the first place, having admirable clarity and resolution. When characters talk in the middle of the frame, the phantom center channel is completely believable and has that locked-in, “right there” quality to it.

She’s not trying to sound like Roberta Flack on this track. Something seemed amiss. Some of the urgency and anger I was used to feeling in this song seemed to be missing. Throughout the review period, I made comparisons using the all-in-one Devialet 120 and the NAD C 510 DAC in combination with either the Rogue Cronus Magnum II or the Rega Elex-R. The Rega in particular conveyed the hardness in Lauryn’s voice more dramatically than the Rotel. It proved difficult to compare the Rotel to a separate integrated amplifier and DAC combination, however, because you cannot separate the Rotel’s DAC performance from its amplifier performance. It seemed more sensible to compare the Rotel to the Devialet and indeed, both all-in-ones have a smoothness to the high frequencies that does not seem to diminish resolution.

THE ROTEL RA-1592 INTEGRATED AMPLIFIER Provides a Wealth of Features and Convenience for a Competitive Price. The Included DAC has a Highly-resolving, Neutral Quality to it and the Powerful Amplifier Should Drive Most Speakers With Ease.

This is a very powerful, fully-featured amplifier. I consistently admired the Rotel’s ability to drive speakers and there was never a moment I felt I could not achieve concert-level volumes if desired. Overall, I’d characterize the presentation as neutral, with an ever so slight polish in the treble. The Rotel is noteworthy for its ability to reveal the many nuances of the human voice, be them in music or video. I was surprised to find how often I used Bluetooth streaming and can report the quality and consistency is excellent.

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Top-grade parts and detailed engineering are used to provide an amplifier intended to compete with the best of separate components.

The Cary Audio Company is based in Raleigh, North Carolina. They have been in business since 1989. They’re best known for their vacuum tube stereo products that are known to be reliable, exceptionally well-built and great sounding. After moving into the digital arena with a brace of home theater products, Cary is now returning to their two-channel roots and offering a solid-state integrated amplifier intended to offer tube sound.

Cary Audio CD-500 CD Player
Cary Audio @ the Las Vegas Audio Show

Integrated amplifiers combine a preamplifier section and a power amplifier section in a single chassis. Some integrated amplifiers can include multiple channels for audio-video use, but the majority (including the SI-300.2d) are stereo, or two-channel devices. Integrated amplifiers can also include other functions. In the past, an AM/FM tuner was also included in the same chassis making it into a stereo receiver.

Because the majority of consumers no longer listen to radio in their homes, and because most now listen to digital sources either streamed from the Internet, wirelessly streamed or from a server computer, it has become common to eliminate the tuner section and substitute a digital-to-analog converter, known as a DAC.

Cary Audio has included a DAC from their premium products in this integrated amp. The chip itself, an AK4490EQ from the Asahi-Kasei Microdevices Company, has a good reputation. It sports proprietary TruBit™ up-sampling and OSO™ re-clocking features. The intent of up-sampling is to increase the frequency of the audio signal so that more gradual filtering can be employed. The DAC also increases the bit depth of an incoming signal to 32-bits for greater resolution. The purpose of re-clocking the digital signal is to prevent jitter from affecting the audio output.

Digital inputs include Cary’s XMOS USB input, capable of true native DSD signals up to 256kHz and PCM/DXD up to 32-bit/384kHz. The integrated amp also offers two coaxial inputs, one optical input, an AES/EBU input and Cary’s aptX® Bluetooth input. All S/PDIF and Bluetooth digital sources allow for 10 TruBit™ selectable up-sampling rates and PCM-to-DSD conversion options.

The preamplifier runs in Class A mode to minimize crossover notch distortion.

The Class AB power amplifier section provides 300 watts-per-channel into eight ohms, 20Hz-20kHz. Into four-ohm loads, the power amp provides 450 watts-per-channel at the same bandwidth. This is not indicative of any power supply limitation, but rather a limit imposed by the heat dissipation fins. The best power amplifiers can double their eight-ohm power output at half the impedance, and were it not for the heat sinking limit, this Cary could also. At these outputs levels, distortion (SMPTE-IM) is specified at less-than 0.5%. This is a completely academic specification since nobody will ever be listening at full power.

One specification that is spectacular is how quietly the Cary runs, sporting a greater than 100 dB signal to noise ratio. This spec ensures that there will be no background noise heard from the amplifier at any reasonable volume level. And listening bore this out. With no signal through the amplifier, and with the volume control set to 100%, no audible noise could be heard at the speakers.

It also bears mentioning that the SI-300.2d successfully drove Martin Logan hybrid electrostatic speakers. These speakers have a 20kHz impedance of only 0.6 ohms. Despite this, it never became exceptionally hot, shut itself down or hiccupped. Another power amplifier blew its output devices when hooked up to the speakers, but the Cary remained unflappable.

The front-panel display also merits some conversation. The panel on the left-hand side of the central volume control knob displays information about the input selection, DAC frequency and volume. Changing sources temporarily blanks the left panel and displays a much larger name of the newly-selected input. The large text persists for a second or two. This is very handy because at its normal size, the left-hand panel text can be hard to read. The panel on the right-hand side of the central knob displays a pair of illuminated virtual power-output meters.

And this brings up one of my (very few) complaints about this integrated amplifier. Most of the time, the meters can’t be readily seen from across the room, so they’re not particularly useful. Furthermore, the meters are significantly brighter than the function display to their left, and can sometimes glare badly enough to make the already hard-to-read function information even harder to understand. I wish that Cary had made the power meters a defeatable feature. I’d much rather have larger, more legible source, DAC and input information than the meters.

But the meters are a “gee-whiz” feature, and I can understand how many users might like them.

Well, this section is easy – I took the amplifier out of its box, placed it on the equipment stand and connected the speaker wires, and an input coaxial cable, and voilá – Music!

A few days later, after the amp had played long enough to be burned-in, I took the time to read the owner’s manual. No surprises. Everything works as expected.

Eventually, I hooked up some analog sources via XLR to try different, outboard DACs. I also tried out the TOSLINK optical connection. The SI-300.2d sounded just as good either way.

I also took the time to pair my phone with the Cary via Bluetooth to stream some CD-quality audio. The sound was indistinguishable from the other inputs. So even though I was initially highly skeptical of sound quality over Bluetooth, the amp surprised me again.

The back panel is well laid out and easy to hook up. I particularly appreciated the availability of not one but two XLR inputs. I tried the Cary’s DAC with both coaxial and TOSLINK optical inputs – no audible difference. Those wishing to drive more than one pair of speakers might wish for a second set of speaker terminals, but I didn’t find that to be a concern.

Note also that the SI-300.2d offers digital outputs in both coaxial and TOSLINK optical flavors. This makes it easy to daisy-chain components if you need to do that. A cinema bypass option allows it to be used as a power amplifier for home theater systems.

Having a set of preamp output jacks is also helpful if one wants to run subwoofers in parallel with the main speakers. Since there is no bass-control filter, the pre-out jacks are full-range, and any subwoofer blending will need to be done using the plate amplifier on the sub.

Looking inside, I was particularly impressed with the toroidal transformer, the clean layout and the heavy-gauge speaker wiring. Many components skimp on power supply and speaker wiring (ever looked inside an AV receiver?). The Cary seems exceptionally well-designed and built. This level of build quality goes a long way toward explaining its premium price.

As mentioned earlier, one of the first speakers that I used with the Cary was a pair of Martin Logan Impression ESL 11A loudspeakers (review here – [insert link to ML review on Secrets website]). These speakers are difficult to drive for some amplifiers because of their decreasing impedance in the treble. In fact, it drops all the way to 0.6 ohms at 20,000Hz. Since most amplifiers aren’t rated for less than four ohms, this is WAY out of the design envelope for most amplifiers. Some amps absolutely cannot drive this load, but the SI-300.2d did so without complaint. Even at the end of some long and loud listening sessions, the heat sinks, though warm to the touch, were not really hot. This argues for conservative design and exceptional stability in its power amplifier section. Bravo!

Now that said, even though the Cary could drive the very particular Martin Logan speakers, and even though it sounded better with them than either of the tube amps I had in the house, you could still hear that it wasn’t necessarily a happy date – for either the speakers or the amp. Yes, they sounded good, and yes, the Cary drove them without complaint, it just lacked the magic one would expect from $16,000 worth of equipment.

It isn’t the fault of the speakers – and it isn’t the fault of the amp. Sometimes you just get an uneasy match. It’s like being asked to tango with your girlfriend’s mom – slightly uncomfortable for everyone…

But THEN I hooked up the Cary with a pair of speakers that I thought would be equally unsuitable – and for all the opposite reasons. Those speakers were the Tekton Pendragons.

Where the Martin Logans had low impedance, the Pendragons were an easy-to-drive 8-ohms. Where the Martin Logans had self-amplified bass, the Pendragons were a completely passive speaker with two 10-inch woofers. The Pendragons are highly efficient, and since they demand so little from the amplifier, I didn’t expect too much when I hooked them up to the very-high-powered Cary. In fact, I even expected a bit of background noise, and possibly some glassy-sounding midrange (which is what I’ve heard from several other high-powered amps using these speakers). What I actually got was something more than expected.

Let me be up front, here – I’m a tube guy. That’s just how it is. I like the sound of tube audio and have owned some pretty high-end solid-state amplifiers before that just didn’t do much for me. Even the ones that I kind of liked eventually wore out their welcome and took that lonely hike to eBay. Now given that set of internal prejudices, I was prepared to give the SI-300.2d a great big yawn.

But what I heard was different! I didn’t expect the amp to sound like tubes, and despite Cary’s stated attempt to achieve that, this amp does NOT sound like a tube amplifier – except for two very important aspects…

The single most attractive aspect of tube amplification for me, is that the soundstage becomes significantly more expansive. And the Cary nailed that aspect just fine, thank you. With the Cary in the mix, the Pendragons disappeared – just as they do with my favorite pair of tube amps. Close your eyes – you can’t point to the speakers. You’re just immersed in a soundstage that not only appears in front of you, but that seems to wrap around on both sides. Marvelous!

Another attractive aspect of tubes I admire is their ability to provide realistic dynamics, even at lower volumes. Horn speakers do this well, but you pay for that dynamic ability with coloration. The strength of the Pendragons is that they can give you a large portion of those low-volume dynamics without the coloration but ONLY IF the amplifier is up to the task. The Cary is! No, it still can’t rival the best of my tube amps, but it is most of the way there (and without the tubes’ romantic colorations).

So although the Cary brought out the Martin Logans’ transparency, it lacked the bass slam of the tube amps. Now (with the hybrid Martin Logan speakers) this may not be a valid criticism because they have self-amplified bass and the Cary isn’t driving them directly. But the Martin Logan bass had LOTS more slam with the tube amps despite them being self-amplified.

The Cary brought out the imaging AND provided tight bass with the Tekton Pendragon speakers. To see if I could determine why, I added a third pair of speakers to the mix: Axiom Audio M-100s.

And once again – the Cary showed its mettle by providing both the generous soundstage and low-volume dynamics that I’ve not previously heard from a solid-state amplifier. I’d like to hear the Cary with some imaging-champ speakers like KEF Blades or Thiel 3.7s!

• MacBook Pro running JRiver Media Center 22
• Red Book CD collection ripped in WAV format
• Oppo BDP-105 used as a DLNA (Ethernet) DAC
• SACD discs played via the Oppo
• iPhone 6+ with Bluetooth enabled
• Cary SI-300.2d integrated amp with built-in DAC
• Martin Logan Impression ESL 11A speakers
• Tekton Pendragon speakers
• Axiom Audio M-100 speakers
• Interconnects from Audioquest, Emotiva, BlueJeans Cable, and others
• Factory CaryAudio power cord
• Speaker cables from BlueJeans, Nordost Flatline, Straightwire Symphony SC, and others

The sound of the SI-300.2d, if I had to sum it up in a word, would be “subtle.” It can run with most anything in some parts of the frequency spectrum, and is always a good imaging amp, but it’s very hard to separate the impressions of the DAC from those of the amplifier itself.

If I had to judge, I’d say that the preamp/power-amp section is very neutral. The DAC has some voicing available via its many oversampling and DSD options, and some experimentation is probably needed to select the option that best matches your speakers.

Gordon Lightfoot’s classic The Wreck of the Edmund Fitzgerald is well-recorded and has a multitude of (sometimes subtle) special effects going on in the background. Above it all, Gordon’s guitar should have audible overtones. I found the treble on this cut clean and impressive.

Henry Mancini’s The Pink Panther Theme is a good example of a well-recorded orchestra with lots of treble and sparkle to be appreciated.

Itzhak Perlman’s rendition of Paganini’s Caprice No. 1 in E, Opus 1 is my standard for overtone reproduction. The violin should be startlingly present, and the overtones should be audible above the resonance of the violin body.

It’s A Beautiful Day’s rendition of Bombay Calling is another view of violin overtones, in a completely different context. Amplifiers or speakers that lack treble extension will shut this cut right on down. But the Cary makes the song sound open and extended.

The Glenn Miller Orchestra’s String of Pearls is not only a familiar classic, but the horn section is a marvel. Listen for separation of brass instruments – they should sound like a group of individual horns – not just a massed blob.

Herb Alpert’s The Lonely Bull is another familiar classic, and again the horn section is the thing to listen to. The music should swell and dip, sounding as if you’re at a live performance.

Jackson Browne’s Our Lady of the Well is a far more delicate song. His voice should be in the room with you, and should not sound different in timbre despite its swings in volume.

And what midrange tour could be complete without the king of them all – James Brown’s I Feel Good (I Got You) is a song I’ve appreciated since I was a child (I used the soul screams to irritate my mom). This may not be the very best recording in the world, but it’s definitely one of his best performances. Listen for the details in both the band and in the voice. Don’t hear any detail? Maybe you need a Cary Audio amp…

George Thorogood and the Destroyers’ live performance of One Bourbon, One Scotch, and One Beer is a song that you’ll either love or hate – but the bass slam in the song is not to be denied. I like this song as a test for amp and speaker combinations – many combos that can do chamber music well just lose it completely when asked to play live rock. Rock doesn’t get much more live or raw than George. I played this for a friend on my system, and when he went home he played the same song for his wife. After seconds, they both decided they didn’t want to listen – their system just couldn’t do it justice. The SI-300.2d with the Pendragons rips this one right on up!

Herbie Hancock’s Dis Is Da Drum has tremendous low-bass slam. The recording shows its age, but the bass is impeccable. If your amp can’t do low bass slam, you’ll never hear this as it was intended. The Cary brings the bass.

James “12-inch” Andrews and the Crescent City All-Stars’ rendition of When the Saints Go Marching In (titled Funky Saints) is another song that just doesn’t sound right with insufficient bass. The Cary does it proud.

The previous three selections focus on bass quality. But the truest test of bass quantity is found in Lady GaGa’s Dance In The Dark. When the bass synth/drum comes in toward the beginning of the song, you’ll find out things you never knew about your amplifier, your speakers and your room. If you have peaks in your response, the bass will become pure mush. If your speakers can’t reproduce low bass at volume, you’ll get the same mush. If your amp can’t control the woofers? More mush. But when things are right – oh my! The Cary gets this right too!

Luther Kent’s Cold Gritz and Blackeyed Peas band hit their peak in about 1970. Their radio hit at the time was Bayou Country. I recorded it off the airwaves and sent a cassette tape to my former schoolmate serving in Vietnam. He mailed me back that it was his squad’s favorite party song. The backup hotties (the Blackeyed Peas) should sound distinct from Luther’s front & center wail. The guitar should sound ethereal. The SI-300.2d brings the magic!

Hank Williams Jr. does Mind Your Own Business with a cast of characters. See how many you can recognize from their voices. The Pendragon/Cary Audio combination make this sound like a live stage show.

The 59th Street Bridge Song by Harpers Bizarre was a big radio hit in its heyday. And despite that, it is well-recorded. I can’t imagine ANY current radio hit being well-recorded, but I digress… The instruments and vocals in this cut should be startlingly distinct. The Cary gets the separation correctly.

One of my favorite recordings is the Bagels and Bongos CD by the Irving Fields Trio. The particular cut Belz contains not only wide dynamic range, but also space between the musicians. See if your setup can separate the trio members. The Cary handles it just fine.

Since I lack the equipment to bench-test electronics, I’ll refer you to Cary Audio’s website for any measurements (beyond the published specifications) that you might be interested in.

I did try all of the up sampling and DSD conversion options of the Cary’s DAC. I couldn’t say which was best, because all sounded close, but I generally preferred the highest available up-sampling without DSD conversion. Could I have picked out my favorite in a double-blind test? Probably not, but spending some time with each of the options (and keeping good notes) can help.

At this level, value is somewhat difficult to evaluate. There are a LOT of integrated amplifiers for far less money. And there are a LOT of separate preamp/power-amp combinations for less money. But think of what the Cary Audio SI-300.2d does that those other components can’t:

• It has much of the soundstage and dynamic capabilities of tube componentry
• It has proven itself to be bulletproof when driving difficult loads
• It is the best-sounding integrated amplifier that I’ve yet heard
• It has a DAC that could easily cost more than the entire price of this integrated amp

Taking into account all the above, I’d have to say that the Cary Audio SI-300.2d IS worth its asking price. I’ve heard nothing for any lesser price that can compare.

The Cary is truly two products in one – a versatile and future-ready DAC and a muscular integrated amplifier. Both are exceptionally high-quality, and they sound that way. The DAC can vary its sound signature somewhat with multiple oversampling options. So unlike many high-end DACs that have only one voice, the Cary’s DAC can be tweaked (and from the listening position by remote control) until you find the best match for your system. The integrated amplifier section is FAR more robust than many preamp/power-amp combinations. The separates not only cost more, but also lack (in many cases) the low-impedance stability that the SI-300.2d exhibits.

Cary states that their design with this amp was to be a solid-state component that had the best of tube sound. And despite the fact that you’ll not mistake this amplifier for a tube component, the Cary does bring sound-staging and dynamics that are quite tube-like.

By any consideration, the SI-300.2d is a smashing success. It’s the best integrated amp that I’ve heard and certainly warrants a serious listen if you’re considering spending anywhere near its $5,995 list price.

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