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Equipment Review
May 2004

Atma-Sphere MA-2 Mk II.3 Mono Amplifiers

by Marc Mickelson

"The MA-2 Mk II.3s reproduce music with command of all its elements."

Reviewers' Choice Logo




Review Summary
Sound "Abundant purity, the sense that I was hearing more of the authentic musical signal and less of that signal overlaid with artifacts of reproduction"; "the naturalness and high resolution of the MA-2 Mk II.3s were astonishing"; uncongested, transparent midrange coupled with "a deep, arcing soundstage and supreme delineation of images"; the bass "was as tight as the recording would allow and offered agility, weight and impact that certainly belied all those tubes."
Features "A fully class-A, differentially balanced design based on the circlotron output circuit, which designer Ralph Karsten has spent over 25 years refining"; power output is rated at "220 watts into 4, 8 or 16 ohm loads from 2Hz-85kHz (+/- .5dB)"; no circuit boards -- "point-to-point wiring rules"; switchable input impedance and negative feedback.
Use Use "a whopping 26 tubes per chassis -- 20 6AS7G output and six 6SN7GT driver tubes" -- so "the MA-2 Mk II.3s put out a lot of heat and correspondingly consume a lot of power -- 800 watts each"; "you need two power cords for each amp."
Value "The wherewithal needed to purchase…is considerable," but "to settle for such amps is the thing of which audiophile dreams are made."

Compared to most people I know, I am a lightweight when it comes to dreaming. I go most nights without any subconscious activity, and when I do dream, I often bore even myself with the story line. I do mundane things with people I know or have never met, and only very rarely do I dream of something that's frightening or otherwise emotionally stirring.

Perhaps my lack of dreaming has to do with being an audiophile, which is all about chasing a single waking dream: reproducing the sound of live music at home. Interpreting the meaning of dreams is inexact business, no matter what mental-health professionals say, and so is reviewing audio equipment. We can measure it, listen closely to it, formulate theories on it, and even write about it, but in the end we can't predict how any one listener will react to a particular component -- such is the power of preference. As reviewers, all we can do is report on the experience of using a particular product, and most importantly describe its sound as accurately as we are able, leaving the interpretation to you. Any reviewer who tells you that the goal is something other than this is either sleeping on the job or dreaming up a way to justify being lazy. Beware.

In dreams begin responsibilities

My first firsthand encounter with an Atma-Sphere amplifier came a little over two years ago when I reviewed the MA-1 Mk II.2 monoblocks. Those amps, like the MA-2 Mk II.3s under review here, are a fully class-A, differentially balanced design based on the circlotron output circuit, which designer Ralph Karsten has spent over 25 years refining (and has patented under the name Circletronic). Specifications for the MA-2 Mk II.3 are gaudy, especially for an output-transformerless design: a claimed 220 watts into 4, 8 or 16 ohm loads from 2Hz-85kHz (+/- .5dB); less than .05% IM distortion at full power; less than 1% THD. And how about this for claims: "The MA-2 Mk II.3 tracks a dynamic waveform faster than any other amplifier known in the world. It extracts more detail than designs that use transformers, transistors and single-ended (asymmetrical) circuits."

Each MA-2 Mk II.3 measures 10"H x 17"W x 28"D and weighs 103 pounds. There are no circuit boards in the amp -- point-to-point wiring rules. If you own a pair of these amps and haven't taken off the bottom plate to look inside, you're missing work that's so meticulous the person who wires the amp signs it. But this comes at a hefty price: $33,000 USD per pair. If you own a previous version of the MA-2, Atma-Sphere can update your amps all the way to Mk II.3 status. According to Ralph Karsten, the .3 version uses a new driver power-supply configuration that includes regulation. The .3 power transformers are lower noise, and overall the amplifier's signal-to-noise ratio is 10dB better. There's also switchable negative feedback -- more on this below. Some of the later MA-2 Mk II.2s have a few of these features, but they don't have all of them. As a consequence, earlier versions are more expensive to update, with the cost varying between $400 for a later unit to $800 for an earlier one. The warranty is reactivated if the amplifier is updated to the current specifications, so you not only get a new amp, you get a new warranty.

Unlike the MA-1 Mk II.2, the MA-2 Mk II.3 has a traditional faceplate, and its connections are around back, not on the front of the amp. However, the look is still unorthodox -- captured-Russian-submarine chic, each MA-2 Mk II.3 sporting a matte "Wrinkletex" finish and a large meter on the front. The MA-2 Mk II.3 uses a whopping 26 tubes per chassis -- 20 6AS7G output and six 6SN7GT driver tubes. As you can easily guess, the MA-2 Mk II.3s put out a lot of heat and correspondingly consume a lot of power -- 800 watts each. However, I found that in my large room, even with the amps running for several hours, the temperature didn't budge enough for me to notice. This was contrary to my experience with the MA-1 Mk II.2s, which raised the temperature of my previous 12' x 24' listening space five degrees.

Bias and DC offset are adjusted via pairs of spring-loaded toggle switches and pots, and that front-mounted meter. I won't go into details -- it's easy to do. Other front-mounted controls are for switching between off and standby, and between standby and operate. I liked the standby feature, which allowed swapping cables without having to turn the amps off completely. Both the switches and their corresponding indicator lights look like those you'd see on a control panel in a Godzilla movie: "When I flip this switch [lips begin moving], our entire arsenal of Z-1 rockets will launch, and the monster will be exterminated!" Of course, in the movie, it never works.

Around back are where things get a little tricky. First, because the MA-2 Mk II.3 is fully balanced, it operates at its peak with a preamp that's also fully balanced. In this regard, Atma-Sphere gives you the choice of input impedance: either 200,000 or 600 ohms, the latter being the professional specification for balanced signal transmission. If your preamp is fully balanced and adheres to the 600-ohm specification -- Atma-Sphere's MP-1 Mk II does, my Lamm L2 does not -- you'll want to use the 600-ohm option (there's a two-position switch for selection). One of the benefits of this is that the interconnect between preamp and power amps becomes non-critical; that is, it's pretty much impossible to hear any difference between interconnects used in this location. Ralph Karsten recommends plain-Jane Belden balanced cables to his customers who own his amps and preamps. For those whose preamps don't offer balanced connections, the MA-2 Mk II.3s can also be used single ended (with shorting pins between sockets 1 and 3 of the XLR connector). I tried both with the Lamm L2 and preferred balanced connection (with 200,000-ohm loading). It sounded slightly more dynamic and quieter.

After you've decided on how to connect the MA-2 Mk II.3s to your preamp, you then need to connect your speakers and experiment with the three-position negative-feedback switch on the amps' rear panel. The MA-2 Mk II.3s are said to drive 4-, 8-, and 16-ohm loads, which should make the amps acceptable mates for most speakers on the market. However, they are OTL designs, and as such are most suited for use with high-impedance speakers. You can adjust the amps' negative feedback to 0, 1 or 2dB. Among other things, adding negative feedback reduces the amplifiers' output impedance and increases their damping factor, helping to optimize them for use with various speakers. I used the 0dB setting with all of the speakers I had here, and for the most obvious reason: it simply sounded best.

Also around back are pairs of fuse holders and IEC power-cord receptacles. That's right -- you need two power cords for each amp.

Review system

I used the MA-2 Mk II.3 amps with a number of speakers, including ProAc Response D38s and Energy Veritas V2.4i's. But for the most part, the amps drove Wilson Audio WATT/Puppy 7s, and near the end of the review period MAXX Series 2s. I had heard Atma-Sphere MA-1 Mk II amps driving original MAXXes when I visited Wilson Audio in 2001, so I was especially interested in hearing the more powerful MA-2 Mk II.3s driving the newest MAXXes.

Electronics were my reference Lamm L2 Reference preamp and ML1.1 mono amps, the latter of which I compare to the MA-2 Mk II.3s, along with an Atma-Sphere MP-1 Mk II preamp. Source components were Esoteric DV-50 and UX-1 universal players, and a Mark Levinson No.37 transport/Zanden Audio Model 5000 Mk III DAC digital combination, which was connected with an i2Digital X-60 coaxial cable. Interconnects and speaker cables were Nordost Valhalla and DH Labs Revelation and Q-10. Shunyata Research's power cords (Anaconda Vx, Anaconda Alpha and Taipan) and Hydra Model-8 provided juice to all components, although I also used the MA-2 Mk II.3s' stock power cords for a while because I didn't have four of any one Shunyata model on hand. Grant Samuelsen of Shunyata Research, who owns MA-2 Mk II.3s, let me know that I could connect an Anaconda Alpha to the bottom IEC receptacle and another Shunyata power cord to the top with no sonic penalty, so that's what I eventually did.

Because of the MA-2 Mk II.3s' physical size and weight, I had no stand or rack on which they would fit, so I set each amp on a pair of shelves from a Target equipment rack that rested on the carpeted floor of my listening room. Putting any amp directly onto carpet is a no-no, as doing so will restrict airflow under the chassis. It's downright dangerous with amps like the MA-2 Mk II.3s that put out a considerable amount of heat.

A dream come true?

Most of the time, reviewing audio equipment involves much careful listening to a component before writing even a few words about its sound. You want to avoid snap judgments, and you also don't want to end up reviewing a new product only against what it replaced -- no useful context there. But there are rare cases in which a product sounds so utterly correct that it requires no acclimation. Its extreme fidelity and rightness are immediately obvious as being closer to the musical truth, at least your dream of it. Such was the case with the MA-2 Mk II.3s, which right from the start addressed just about every parameter I consider important to musical reproduction in a very positive way -- and progressed from there.

I'll begin by talking about a strength of tube amps in general and OTL amps in particular -- the midrange. I had heard the MA-1 Mk II.2s, so I thought I was prepared for what the more powerful Atma-Sphere amps would do through the fat part of the frequency range, but the MA-2 Mk II.3s were in a category of their own in this regard. The transparency and uncongested qualities I noted of the MA-1 Mk II.2s were alive and well, but they were joined by an obvious and abundant purity, the sense that I was hearing more of the authentic musical signal and less of that signal overlaid with artifacts of reproduction -- noise of various kinds, including fine grain and the coarseness it can effect. This, to my ears, is what separates good and very good audio equipment from great, and while it's not easy to pin down with the terms we have at our disposal (except to say that the sound lacks certain things we've grown accustomed to hearing in various degrees), it's obvious when you hear it, and it's obvious that the MA-2 Mk II.3s express it. And by definition, that purity is present with every recording. It exerts its influence on every signal that passes through MA-2 Mk II.3s and on every sound the amps reproduce.

So from the very beginning, listening to music over these amps was an enlightening experience, not just for what I was hearing the amps do, but also for what I was gleaning from the recordings I was playing -- their musical entirety, not merely a collection of previously unnoticed details. I've mentioned John Hammond's Wicked Grin [Pointblank 7243 8 50764 2 8] in various reviews, and it never sounded more alive than through the MA-2 Mk II.3s. The soundstage seemed to grow in all directions at once. Hammond's voice was big and radiant, and his guitar on "Get Behind the Mule" in particular resounded throughout my listening room with raw power and steely sheen. There was beautifully executed attack followed by decay that resembled life in its quality and duration. Even at very high volumes the sound was clear and comfortable, prodding me to put on disc after disc just to hear how they would be portrayed. The naturalness and high resolution of the MA-2 Mk II.3s were astonishing. Some solid-state amps may sound more detailed (often because of an inherent gaunt starkness), and some tube amps will sound more gentle (the product of greater sweetness, perhaps to excess). The MA-2 Mk II.3s are both detailed and gentle, but in ways that are utterly and musically right.

Another semi-revelation was the MA-2 Mk II.3s' bass, which was as tight as the recording would allow and offered agility, weight and impact that certainly belied all those tubes. These amps can move air, but as with the midrange, the bass is detailed and varied with each recording. I am convinced that some listeners will prefer it to even "the best" solid-state bass -- it's fully integrated into the presentation, not an attention-grabbing element of the sound produced. As I listened to "I Love the Life I Live" from Buddy Guy's Blues Singer [Silvertone 01241-41843-2], all I could do was enjoy the gutsy, swinging quality of the low frequencies. Guy's voice was anchored between the speakers amidst a vast, reverberation-filled space; calling this "a strong center image" just wouldn't do. Gavotte in D Major from Jacques Loussier's Plays Bach [Telarc CD-83411] didn't display any of the low-frequency mushiness and overhang it can (Telarc recordings are often on the bass-heavy side of things). Instead, and surprisingly, the MA-2 Mk II.3s reproduced the drums strikes, as they flew between the left and right speakers, with the initial impact and trailing weight perfectly intact. I've heard this done with more pizzazz, but I can't say I've heard it done any better. I'll take better.

Another recording I'd never heard reproduced better was Ted Hawkins' The Next Hundred Years [Mobile Fidelity UDCD 702], which showcased a deep, arcing soundstage and supreme delineation of images, especially Hawkins' friendly, textured voice. The MA-2 Mk II.3s reconstructed the soundstage on each recording with great precision, not the perception of precision that comes from a tipped-up or edgy presentation. Instead, there was spread right to left and front to back, all of which helped impart an exacting reconstruction of reality, or at least as much of it as I could discern given that I wasn't at the recording sessions. It's just not enough to say that the soundstage cast by the MA-2 Mk II.3s was huge or that the images in it were palpable. These were certainly true, but they don't explain well enough the way these amps suspend disbelief with well-done recordings or convey the totality of the music on all recordings, even poor ones.

In fact, explaining much about these amps is a challenge. They evoke such a strong positive reaction, but why? There is one word that helps describe it, for me at least: authority. The MA-2 Mk II.3s impart the foremost sense of reality I've heard, no matter the circuit or technology. This is certainly due to the traits I've mentioned -- the detail, transparency, clarity and naturalness -- but it goes beyond these, to the way the MA-2 Mk II.3s reproduce music with command of all its elements, representing what's on the recording and promoting a connection with the listener. We all know people who speak with authority; the MA-2 II.3 monoblocks are amplifiers that do as well.

I mentioned above that I used the MA-2 Mk II.3s with ProAc, Energy and two different Wilson Audio speakers, and the amps sounded terrific with all of them. Each speaker retained its unique characteristics, the sound of the Atma-Sphere amps never overshadowing them. Perhaps it's no surprise that the MA-2 Mk II.3s and Wilson MAXX 2s were the most impressive combination. (How impressive? Details in the upcoming MAXX 2 review.) However, I greatly enjoyed the amps driving the ProAc Response D38s as well, which sounded their best with the power and clarity of the MA-2 Mk II.3s behind them. This combination made a strong case for spending the bulk of your audio budget on amps. In terms of preamps, the Lamm L2 turned out to be a very good partner for the MA-2 Mk II.3s, matching the amps' naturalness and high resolution, especially through the midrange. However, Atma-Sphere's own MP-1 Mk II sounded similar tonally but bigger and more definitive in the bass region, where the presentation took on greater weight and impact. Because of its central position in an audio system, a preamp like the MP-1 Mk II, which has only balanced outputs, may prove problematic, but it's the perfect functional mate for the fully balanced MA-2 Mk II.3 amps, and its sound is complementary to the extreme. The bloom and low-frequency beef of the Atma-Sphere preamp made for extraordinary sound.

Tube titans

One of the amps you should hear if you are considering spending $33,000 for a pair of MA-2 Mk II.3s is the Lamm ML1.1 ($22,690 per pair), which I reviewed shortly after its debut a year ago. The ML1.1 is a great amp -- a Reviewers' Choice -- but for very different reasons than the MA-2 Mk II.3s. While the latter are essentially one-third more expensive, I would think that anyone considering purchase of the ML1.1s could spring for the MA-2 Mk II.3s if he or she really wanted them. The wherewithal needed to purchase both amps is considerable.

First, the big-picture stuff. The Atma-Sphere amps are much more powerful than the ML1.1s, which are rated at 90W each, and it shows. The MA-2 Mk II.3s have greater dynamic capabilities, sounding more lively at low levels and able to reach a plateau of loudness that the ML1.1s can't attain. Both amps are very quiet, or rather the perception of both being quiet amps is nearly equal. For both, the music emerges from a very black background, although the Lamm amps are a touch more proficient in this regard. Another similarity is that both amps convey abundant naturalness, their overall presentations always sounding poised and whole.

It's when the traits of these two amps are compared that a number of differences emerge. Tonally, the Lamm amps sound a little darker, although this applies to both amps in an absolute sense (taking into account the number of brighter-than-neutral solid-state amps on the market). They also sound more full than the Atma-Sphere amps, and more intimate in the process. The MA-2 Mk II.3s can cast a larger soundstage, this depending on source material, and offer a more airy and lively portrayal, in contrast to the Lamm amps' more gentle, less incisive delivery. Images from the ML1.1s, for instance, are softer, not as strongly drawn. The ML1.1s' bass is very good in terms of weight and fullness, but it's real strength, like that of the MA-2 Mk II.3s, is the way it meshes with the rest of the presentation, never calling attention to itself. But even so, the Atma-Sphere amps offer greater low-end definition and tautness, definitely greater power, and a more satisfying portrayal of music's timing and flow, as carried along by upright bass, bass guitar, and drums.

My admiration of Lamm electronics is conspicuous -- I've owned and used various Lamm amps and preamps for years, and mentioned them in my reviews as well. The naturalness of the ML1.1 and the discontinued M1.1 monoblocks, both of which I've reviewed, is apparent to those listeners who value such reproduction. Add to this list, and place at the top, the Atma-Sphere MA-2 Mk II.3, whose only competition in a cumulative sense (and based purely on my experience) are the very different Lamm ML2 single-ended-triode monoblocks.

Lights out

Even though I had heard the Atma-Sphere MA-1 Mk II.2 monoblocks, I wasn't fully prepared for the magnificent sound of the MA-2 Mk II.3s, which have firmly established themselves as one (or two) of the very best-sounding amps I've heard and by far the most complete OTL design I've encountered. I enjoyed the sound of Tenor Audio's 75Wi OTL monoblocks -- an understatement given that we named those amps our Aesthetics & Sound award winner for 2002. Yes, it's been a while since I heard the Tenor amps, but I know I wasn't as bowled over by them as I am by the MA-2 Mk II.3s, whose resolution and purity -- among many other sonic goodies -- have set new listening standards for me. I've heard many very good amps and a few that are great; as I type this, I'm convinced that the MA-2 Mk II.3s are the best of them all.

Ralph Karsten introduced his gargantuan two-box MA-3 monoblocks at this year's CES, and while these new amps represent the top of the Atma-Sphere line (they'd better at $87,000 per pair), I hope they don't overshadow the great achievement of the MA-2 Mk II.3s. To "settle" for such amps is the thing of which audiophile dreams are made.

...Marc Mickelson

Atma-Sphere MA-2 Mk II.3 Mono Amplifiers
$33,000 USD per pair.
Warranty: Three years parts and labor, one year for tubes.

Atma-Sphere Music Systems
1742 Selby Avenue
St. Paul, MN 55104
Phone: (651) 690-2246
Fax: (651) 699-1175

E-mail: ralph@atma-sphere.com
Website: www.atma-sphere.com

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