The Japanese call it kaizen -- change for the better. The English translation is "continuous improvement." In high-end audio, look no further than the work of Ralph Karsten and Atma-Sphere to see kaizen in action. Here is a guy who has been refining the same circuit for almost 30 years -- Atma-Sphere’s patented Balanced Differential Design.

It was 1989 when Atma-Sphere introduced the first Music Preamplifier 1 (MP-1), and 18 years later a new version of this full-function preamp, the Mk III, was introduced. At its heart the MP-1 Mk III sports an output transformer-less (OTL) Circlotronic output amplifier. This triode-based design incorporates the same tripartite architecture of differential, cascode, and bridge gain-stage circuitry found in Atma-Sphere amplifiers. All Atma-Sphere preamps and amps are true differential designs, fully balanced from input to output. The MP-1 Mk III uses a dual mono topology; in effect, there are discrete gain stages in each channel for each half of the audio waveform.

In addition to being an OTL, the MP-1 Mk III is also an OCL -- it uses no output coupling capacitors. Why forgo coupling caps? Ralph Karsten explained it like this:

The sonic advantage is wider bandwidth and greater detail as the coupling capacitor that would play bass right into say, a 10k input impedance of a transistor power amplifier, would be a prodigious part. It is impossible to get the highs and bass frequencies right with such a big value, regardless of the film type.

Through continuous improvement of his design, kaizen-master Karsten obtained more output from the Mk III version of the MP-1 by incorporating a new main power transformer, a completely new solid-state power supply, and a super-tight high-voltage-regulation scheme. There are now no unregulated supplies in the Mk III. The preamp section is further improved by a new two-stage noise-rejecting constant-current source feeding the gain stages. Ralph even reworked the umbilical connecting the power supply to the control unit.

The MP-1 Mk III ($12,100 USD with phono, $10,950 without) is a two-box affair, both 19"W x 6 1/2"H x 12"D, with a 4' connecting umbilical that is plug-attachable at the 13-pound control unit and fixed on the 21 1/2-pound power supply. The power supply has lights on its front panel indicating wall power and power to the control unit. Around back is an IEC power-cord receptacle. On the control unit’s rear you’ll find only XLR inputs to the phono section. (Your typical phono cartridge is an inherently balanced device, and Atma-Sphere expects you'll use an XLR-terminated tonearm cable.) Cartridge loading is nicely flexible, with terminals to take any resistor values you care to use; otherwise, the default input impedance is 47k ohms. There are two Neutrik XLR auxiliary inputs and two Cardas RCA tape-monitor inputs and outputs. The unit offers a single pair of XLR output connections. Cable-wise, figure to get on the balanced bandwagon if you purchase this preamp. With a simple connector, the MP-1 Mk III can also drive 32-ohm headphones.

The MP-1 Mk III's line stage provides 14dB of gain, and its phono stage delivers approximately 60dB. Atma-Sphere claims its phono section can support cartridges whose output is as low as 0.2mV, and they offer an optional step-up transformer if you need to go lower than that. The preamp delivers 32V into 600 ohms and is capable of driving 200-foot balanced interconnects.

Input sources are controlled through the preamp’s front panel of toggle switches, laid out with their own Spockian logic. Additionally, there is an on-off switch and a toggle that swaps the absolute phase of both channels between normal and inverted. It takes an Atma-Sphere artisan eight hours of work to build the 24-step attenuator that sits on the business end of the front panel’s large volume control -- there is no remote control for the MP-1 Mk III. The attenuator adjusts in 2dB increments, and it’s worth removing the cover to see the craftsmanship. Want to know if your preamp is a true balanced design, or one that just converts signal from XLR inputs to single-ended then back? Check if its volume control is a true four-pole device. Rounding out the front panel on either side of the volume control are smaller channel-balance trim knobs that attenuate line-stage gain but lie completely outside the audio signal path.

Each channel has a complement of four 12AT7 tubes in its phono section and five 6SN7s in the line stage. At startup, the preamp needs about 30 seconds to stabilize while servo circuits detect and correct any DC voltage at the preamp’s outputs. Warning lights indicate if tubes have sections too imbalanced for the circuit to compensate. All grounded components in the MP-1 Mk III get wired in a star-ground topology that inhibits noise and hum.

The build quality of the MP-1 Mk III oozes craftsmanship, and parts are top-notch. The build technician typically signs his work on the interior chassis. All but two of the standard coupling caps are Teflon. The review sample had these replaced with V-Caps, which are an optional upgrade. Other upgrades include a Caddock-resistor package and replacement of all remaining capacitors with V-Caps. Earlier editions of the MP-1 can be upgraded to current spec, which also includes renewal of the unit's three-year warranty. The cost of upgrading varies based on the age of the unit.

Reference system and use

Playback in my system starts with the Transfiguration Orpheus moving-coil cartridge (0.68mV output) mounted on an SME V tonearm, residing on a cocobolo Teres 320 turntable. With its seemingly effortless dynamic contrasts and sublime tonal purity, the Orpheus is one of the great phono transducers of our day, a true music-lover’s cartridge.

The Audio Research PH7 is my current reference phono stage. It applies 57.5dB of gain to cartridge output before handing off the signal to a Conrad-Johnson ACT2 line-stage preamp. SACDs and Red Book discs play on an Ayre C-5xe universal player. The ACT2 connects to the single-ended inputs of twin 140W Atma-Sphere MA-1 Mk III power amplifiers. The phono stage, preamps, and amps get cabled up with Shunyata Antares Helix and Altair interconnects. The amps connect to Audio Physic Avanti Century speakers with Shunyata’s Andromeda Helix speaker cables. All electronics plug into a Shunyata Hydra Model-8 power conditioner using the company's Python Helix and Taipan power cords.

My single-ended tonearm cable was as welcoming as a snooty maître d' to the fully balanced MP-1 Mk III. To the rescue rode Silver Audio’s Max Kreifeldt, who graciously made loan of a DIN-to-XLR Silver Breeze, otherwise identical to my RCA-terminated tonearm cable. Further help came from Grant Samuelson, marketing director of Shunyata Research, who, as we say here in Wisconsin, "borrowed me" a broken-in XLR-terminated version of the superb top-of-the-line Antares Helix interconnect to match my single-ended pair.

Of the many tube preamps and amps that have passed through my system, I found the MP-1 Mk III to be the most tube-sensitive component I have used. All 18 of its tubes are dual triodes, and as a fully balanced design, it prefers each tube to have internally well-matched sections. Without the buffering effect of output coupling caps or transformers, this preamp quickly makes you quite aware of any tube's microphony or noise issues. This is especially true of the 12AT7s in the phono section. When the phono stage is engaged and no music is playing, turning up the volume control can increase the amount of audible tube rush. This becomes more relevant the lower the output of your phono cartridge and the more gain you apply to it. The manual proclaims there are no quiet NOS 12AT7s still available and only modern tubes should be used here.

When the MP-1 Mk III arrived, it had only factory QC time on it, and Ralph noted that it could take four to six weeks to break in. Over the days, its sonic character evolved, slowly -- very slowly -- from faintly angular, tight and closed-in, albeit with plenty of resolution, to relaxed and open. And then, at roughly 120 hours, like a flower that takes a long time to bud, it seemed to make a final burst. Almost overnight, the MP-1 Mk III seemed fleshed out with a newfound smoothness and richness, as tonal colors gained greater depth and subtlety.

To give its best sound, the MP-1 Mk III likes it tubes hot and its power-supply capacitors charged. There are no worries in listening after a few minutes of warm-up; however, I found that the preamp consistently sounded best after being powered on for at least an hour, preferably two.

The sound of music

Having now heard two Atma-Sphere amplifiers in my system (the M-60 Mk III and MA-1 Mk III), it seems fair to say the MP-1 Mk III preamp shares the amps' ability to startle listeners with a clarity of musical reproduction that, on first hearing, is so limpid, so penetrating, that it is difficult to convey in words. This Atma-Sphere sound -- this see-through singularity -- imbues and pervades all aspects of music reproduced through the MP-1 Mk III.

And yet, in the end, the MP-1 Mk III’s clarity is not delivered as a characteristic that it has, but as something that it does -- an overall lowering of the distortion floor, a lessening of the perception of electronica, a getting out of the way of the original waveform, at least as handed to it by an analog or digital source. To appreciate the phenomenological character of this clarity, we can decompose it into its sonic elements. Many of these are no different from music’s fundamentals: dynamics, timing, and tonality. In effect, an account of optimal reproduction is an account of music itself. So let’s listen to some music.

The Budapest Festival Orchestra’s performance of Mahler’s 2nd under the baton of Ivan Fischer, as delivered on a twin-disc SACD from Channel Classics [Channel Classics CCS SA 23506], is a poster child for the viability of the digital medium -- a truly superb rendition. Here is "Resurrection," a very serious second symphony, and here is Gustav, the happy wanderer in a Tyrolean hat, careening in waltz time about the Austria-Italy border, à la Dick Van Dyke in Chitty Chitty Bang Bang, smacking gongs and eating spumoni. What a ride Mahler gives us. From the deep authority of an opening timpani and the lilt of a clownish clarinet in the third movement, to the individuated and dimensional voices of the choir. From gossamer violin pizzicatos and rich woodwind cadenzas, to the roiling pressure wave of massive gong strikes and, at the end, a solo wooden hammer on metal bells. Here, like an obliging doorman, is the MP-1 Mk III, applying its gain, directing the music to the amplifiers, and otherwise getting the heck out of the way. My listening notes are littered with "NSB" -- shorthand for "never sounded better."

Dynamics, timing, gorgeous tonality, sumptuous detail, air and dimensionality -- they're all here. Yet, within this equipoise of attributes, there are characteristics that readjusted my expectations, pushing my system beyond its previous standards. The MP-1 Mk III's capacitor-less coupled output brooks none of the high-frequency softness or roll-off sometimes associated with tube gear. No other preamp I’ve heard delivers as extended, filigreed highs with such air and delicacy. There is no brightness and no bite, just violins, bells, and harps stretching heavenward.

On the other end of the spectrum, the MP-1 Mk III is equally adept. Throughout the Mahler piece, heavy timpani strikes were very realistic. I heard the resonance of their skins within their kettles and the authority of the instrument within the hall. While my speakers’ cutoff point keeps me from fully appreciating Thus Spake Zarathustra’s sub-20Hz opening organ note [RCA/Classic LSC 1806], the MP-1 Mk III delivered timpani crescendos, cellos, and bass with unencumbered power. The very lowest bass could be a teeny bit wooly, but it was never without weight and timbral definition. Listen to the standup bass on NRBQ’s "Rocket in My Pocket" from All Hopped Up [Red Rooster LP1806]. I heard it as deep and tight, with the air and resonance of the bass’s body and nicely resolved decay. Here was that elusive bass with ambience.

Whether ascribed to a lower noise floor or coherent phase, the Atma-Sphere preamp is a superb resolver. I’m not talking solely about tiny details like dropped drumsticks, page turnings, and sneezes in the audience, though these come through in spades. "Air, air, air" -- my notes are filled with references to the space and separation between musicians, the sense of a performance in a hall, the sense of resonant energy hovering above a string section that ripples across the orchestra as the playing shifts from violins to violas. The MP-1 Mk III found a way to resolve the context of a performance, and did so on many levels.

The Mk III is adept at resolving, micro-fine dynamic and frequency changes with coherency and the absence of blur. String sections on Zarathustra displayed that shimmer that only comes from bunches of violinists stroking monofilament with horsehair in time. Musicians and instruments acquired an aural palpability within their venue. I heard the attack of the bamboo reed and percussionists damping their instruments to abate spillover into the next measure. Transients were natural, not incisive, and even in busy passages I heard decay from individual instruments. At their start or end, notes were not smudged across time.

I cashed out this preamp’s resolving power as verisimilitude. It first hit me listening to "Cecilia" on the NRBQ album. There I was, in the club, the band on stage before me, each musician in his space shifting about. The aural holography of the MP-1 Mk III yielded a soundstage with depth, width and height. I sensed the relation of the singer to his microphone. The piano was clear and dynamic as notes came off its sounding board. The sax had that wet reedy grunt in a saxy kind of way. Backing vocalists were dimensional, in space. Not just the tune, but also the band had a natural vivacity. Here were people making music, and it was an event propelled with zest and life. I wish I could capture that experience and let you download it. "NSB" for sure.

With all this truth, don’t think beauty took a holiday. The MP-1 Mk III’s clarity was further understood through music’s rich palette of fundamentals, harmonics and overtones. To my ear, the tonality of the MP-1 Mk III, if it can be said to have such, was highly neutral. It was no warmer, cooler, lighter, darker, or sweeter than the music it transmitted. If you’re looking for the preamp’s 18 tubes to add warmth to an otherwise cool-sounding system, you will be disappointed. I’ll speculate the MP-1 Mk III simply inserts less second-order harmonic distortion (that near silent octave above the fundamental) that typically lends a psycho-acoustic sense of warmth or fullness. Lack of added warmth does not mean washed out or lean. The MP-1 Mk III was as close to neutral, as close to the timbral quality of the source, as possible.

In my system, the Atma-Sphere preamp was virtually transparent to the purity of tonal colors from the Transfiguration Orpheus cartridge. The effect was no more evident than the Mk III’s rendering of the human voice. Listen to the sweet inflection from the blended voices of Dolly Parton, Linda Ronstadt, and Emmylou Harris on their Trio album [Warner Brothers 25491-1] as they sing the last line of "Those Memories of You." The MP-1 Mk III lifted and separated the singers in space, their voices clear, dynamic, and rich. Together their harmony was as visceral as it was exquisitely beautiful. Subtle note bendings from steel guitar and overtones from percussive membranes were there for the hearing. Again, the MP-1 Mk III established new expectations for my system.

Compared to what?

For comparison with the MP-1 Mk III, I used my current reference components: an Audio Research PH7 phono stage ($5995) and Conrad-Johnson ACT2 line-stage preamp ($13,500), both of which have earned SoundStage! Reviewers’ Choice honors and other industry accolades.

In my system, the MP-1 Mk III sounded more similar to than different from the ACT2 alone, the combination of the ACT2 and PH7, and the PH7 used as phono stage with the MP-1 Mk III’s line stage. Differences between compared components were small, but with one exception, not so subtle that I’d mistake one for another. At first, I expected to miss having a remote control with the MP-1 Mk III, but its absence found me less interested in twitching volume and channel balance and more focused on the music.

From instrumental solos to an orchestra triple the size of those in Mozart’s day (not to mention an organ, an alto, a soprano and a large choir), the hour-and-twenty-minute Mahler "Resurrection" covers an incredibly broad swath of sonic geography. Mahler paints his first movement in big strokes, and the ACT2 offered a particularly realistic presentation of the music’s huge dynamic contrasts coupled with the energy and drive of its temporal flow. The C-J preamp proved equally adept at massive timpani crescendos and delicate flute solos. The ACT2 is so well balanced in its character that no glaring inadequacies stand out.

The MP-1 Mk III met the ACT2 point for point on timing and dynamics, while offering more airy, extended highs and -- to the surprise of my ears -- an ever so slightly richer tonality. By comparison, the MP-1 Mk III’s tonal character is a wee shade lighter than the ACT2’s, and the Mk III captured slightly (very slightly) more harmonic nuance. Both preamps excel at soundstage height, width, and depth and easily transmit back- and side-wall reflections. The MP-1 Mk III offered slightly cleaner leading edges in the lower frequencies, though both preamps delivered weighty bass with tonal definition. Both were a bit soft on lowest bass and organ notes.

Listening to DeBurgos conduct the New Philharmonians in Albeniz’s "Austurias Leyenda" from his Suite Espanola [Decca/Speakers Corner 6355], I heard the MP-1 Mk III and the ACT2/PH7 combo deliver this movement with the rocking vivacity of a Queen power ballad. Both preamps shared excellent quickness and a facility for uncongested large-scale dynamic swings. Both delivered that coruscating golden power-punch from trumpets floating high above the right-rear soundstage. Both resolved the percussionist’s after-strike clamp on his cymbals.

Compared to the tandem, the MP-1 Mk III delivered slightly more venue context, with a touch better sense of an orchestra in space, and an overall hint of greater transparency. The Mk III presented slightly better air and blackness between musicians, with a stronger sense of their dimensionality. The notes, like Cartesian ideas, were clear and distinct -- in a nutshell, they sounded more real, but just. Tonally the C-J/ARC pair was a breath more weighty, and yet I found vocal and instrumental timbre from the Mk III slightly more nuanced. Listen particularly to the bells, xylo and celesta on the Albeniz record as harmonics radiate off them in all directions. I’m not sure how to parse this phenomenon, but there it is -- a slender amount more harmonic information inclining more toward the light than the dark.

Listening to the Audio Research PH7 connected to the Atma-Sphere line stage versus using the MP-1 Mk III’s native phono section, there were times when I had to double-check which one I was using. They each have their sonic traits, but differences are very subtle and not ones of fundamental character. The faintest of layers appeared when switching to the PH7 -- one more petticoat, one more mattress between the princess and her pea. Call it a thin brushing of warmth. I was equally impressed with each unit’s fine-spun delineation of pianissimo violins -- a high compliment to the MP-1 Mk III, as until hearing it, I’d heard no finer than the PH7 in this department. With ease, both handle the extraordinary dynamics of the female voice and piano during Emmylou Harris’s spare soliloquy "I’ve Had Enough" on the Trio album. A couple octaves below middle C in the cello’s playground, I heard the MP-1 Mk III a teeny bit cleaner and quicker on the front side of the wave, though both phono sections did a nice job resolving decay.

You can quibble about their differences, but I found each of these components so good that I could live with any combination as long there was a phono stage in the mix. This basket of high-end goodies is a testament to the place held by American ingenuity in the current state of audio’s high-end art. Together the ACT2 and PH7 make beautiful music in my system, and at a near-$20,000 price tag, they should. But the Atma-Sphere MP-1 Mk III is nothing less than a sonic tour de force, and its phono stage is a bargain-priced add-on.

The dessert of discourse

What about the synergy of pairing the MP-1 Mk III with an Atma-Sphere amplifier? Used with balanced interconnects, the result is a true and fully balanced system from phono cartridge to amplifier output. The bottom line is the MP-1 Mk III sounds a lot like the Atma-Sphere amps, and the contributions of each seem to meld together as an unfettered continuum of gain stages. Regardless of technology, pairing the MP-1 Mk III preamp to my Atma-Sphere MA-1 Mk III power amps increased the sonic realism of my system. But the effect was subtractive -- this dynamic duo simply put less between the music and my ears. Together they yielded a distortion floor lower than any combination of gear I’ve used thus far.

During my time with the MP-1 Mk III it worked flawlessly and easily proved itself the finest-sounding full-function preamp to grace my system to date. So in touch with the musical performance did it put me, so addictive was its clarity, that, for me, the MP-1 Mk III recalibrated my expectations for stereo reproduction. I urge caution if you plan to audition the MP-1 Mk III: You may not be able to walk away without it. But you can’t walk away with the one here -- I’m keeping it.

...Tim Aucremann
tima@soundstage.com

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