The Audiophile Voice
Atma-Sphere MA-1 Mk II
Monoblock Amplifiers

Ron Nagle


Not all that long ago I sat around a table in the press room in Chicago's Palmer House sipping coffee with members of the audiophile press attending Hi-Fi '99. Listening to these guys, I got the strong impression that there really wasn't anything new to see or hear. Of course, the digital format wars were raging between the DVD and DSD camps, and not to name names, most critics were coming down on the Sony-Philips side of the debate about sound quality. DSD, now on the market as Super Audio Compact Disc or SACD, would have a difficult doubtful future ahead of it, they said. That was my assessment as well, but I chose to wait it out and let the chips fall where they may. That became background noise for my Chicago adventure with its boundless possibilities. There is so much to discover in the high-end, solid state or vacuum tube, digital or analogue, coming from all corners of the globe, that the permutations are more than enough for one lifetime. These changes present myriad shifting colors, enough to paint a musical masterpiece. My quest for the new and improved swept me down near-countless corridors, past doorways alive with music. And if I paused, it was inevitably to be warmed by the sound of tubes. Now, dear reader, let me introduce you to Atma-Sphere.

Who would have thought that what was once old, could now be new. I remember the words of the master: "You must follow the light, Grasshopper, for there is yet joy to be found in the spiral path." Happy I am to report that the knowledge of the ancients is not lost. In the distant heartlands, in a town named after a saint from the early Christian era, St. Paul; in a state called Minnesota, which is not to be confused with Minnehaha, even though one might grin at the antics of their Governor Jesse Ventura, a refuge from professional wrestling, there is company called Atma-Sphere where the alchemy survives.

The Objet d'art.......icle

The Atma-Sphere MA-1 MKII Monoblocks are rarest among tube amplifiers. Generating 140 watts per side of output transformerless (O.T.L.) Class-A power, they inhabit a niche companioned by perhaps only two or three other but dissimilar OTL designs. The designer Ralph Karsten reminds those inclined to listen that his amplifiers are not variations of Julius Futterman‘s earlier OTL designs, but a patented innovation that he describes with his see-saw analogy. He explains that his design combines two separate single-ended triode amplifiers within each chassis, each 180 degrees out of phase with the other. Thus, you can liken the result to an amp on each end of a see-saw, where one amp is driving up (the positive part of the signal) and the other is going down (driving the negative half).

The result is a differential topology, fully balanced from input to output, with ultra fast reflexes (slew rate) and does not need feedback correction. Atop a polished stainless base, measuring 11 inches wide, 23 deep and 7 high, is a very impressive gathering of tubes. At the front, the inputs go to eight 6SN7 driver tubes, four per monoblock, while the speakers are driven by 28 Sovtek 6AS7G dual triodes, 14 per chassis.

On the rear chassis skirt, you will find along (with the copper binding posts) three power supply fuses. Up front, the skirt holds the functional controls, four toggle switches; there are two large toggle switches, one for plate and the other for heater power, and two smaller toggle switches (each with a corresponding potentiometer), one for d.c. offset adjustment and the other for setting output tube bias to 750 milliamps. There are also two input connectors, a balanced XLR style and unbalanced RCA jacks. Last but not least are two large jewel-style lamps, one amber for filament power, and a red one for plate (operating) power.

In the dim light of my listening room, with all the tubes in place and powered up, the sight of 36 vacuum tubes reminds me of the glow of sanctuary candles. I remember another time another place. I recall the words of the master: "Grasshopper, the path to enlightenment begins as a journey from within."

Within the twin retro-look chrome-and-black chassis I find so appealing, reside neatly laid- out, mirror-image twin circuits that must be highly labor-intensive to produce because of their hand soldering. At the rear, the Cardas solid-copper binding posts are connected to the output by custom wire made exclusively for Atma-Sphere, everything routed and secured by nylon tie wraps. The black crinkle-finished upper cover houses power supply transformers and two massive computer-grade electrolytic capacitors. Wired into the chassis below are Roderstein metal-film resistors and Rel-Cap polystyrene capacitors, which are very competent, far better than average, but perhaps short of the very best obtainable.

According to designer Ralph Karsten, there are three upgrades available. The first uses exotic and expensive Teflon coupling capacitors from Rel-Cap to replace the stock coupling capacitors. The second and far more extensive modification involves replacing all the resistors with top-quality custom Caddock precision metal-film types. And finally, special custom filter capacitors can be used in the power supply. As you might imagine, ideally the upgraded amps should be ordered and made at the factory with these components, rather than having them retro fitted at some later date. Not incidentally, my review samples were completely stock and evaluated in my system with unbalanced RCA-style interconnects.

The Set Up

My whole reference system has evolved and upgraded since my last review. It now is biamped and additionally woof'ed. In addition to a fortuitous addition of a troika of Argent Room Lenses, there is a modified Hafler Mosfet 500 amp which provides 250 watts a side to power the Gradient woofers upon which my Quad ESL 63s main speakers sit.

Now I have many more choices to make in doing this review. I can run the MA-1 amps full range, or if I chose, only listen to them from 120 Hz on up to their high frequency limits. After I position the Atma-Spheres side by side on the floor in front of my equipment rack, I toggled on the heater supply and watched the friendly glow grow. About five minutes later I actuated the second toggle switch to apply the plate voltage and electronic life coursed through the amp's veins.

After approximately five minutes more, the amps should have settled in enough to adjust the d.c. offset voltage and bias. Using the first of the two smaller toggle switches, you first actuate one and adjust the front panel potentiometer to zero the meter. You then hold down both spring- loaded switches and set the operating bias at 750 milliamps with the second potentiometer. All that's needed at this point is the application of a music lover's ears.

Near the end of the MA-1 evaluation, I lost the ability to position the meters pointers exactly on zero which resulted in my inability to adjust the d.c. offset. The potentiometers used for this purpose simply had no effect. The error was small, maybe half an increment of the dial scale, but still it impacted my perfectionistic instincts. It did not seem to affect my ability to adjust tube bias farther upscale at 750 milliamps, and I could detect no sonic penalty because of this but obviously it shouldn't have happened.

A phone call to the designer Ralph Karsten in Minnesota informed me that the manufacturer had over tightened the meter pivots and a simple adjustment by Atma-Sphere would resolve the problem.

The Aural Aspect

First impressions are something I value in my own reviews and those of other critics. For me, they provide a basis for all the subsequent trials and permutations that follow and a portion of them usually endure even as my last word is written. However, what follows are quotes culled and condensed from many pages of notes. As I began, I remembered the old one's advice, "Learn to listen, Grasshopper, for the unknown."

Full range with the MA-1 amps driving the Quads: "The overall tonal balance shifts, bass now more prominent and extended. The effect is to warm the music even to the extent that high frequencies seem limited." Over a span of listening time and aided by careful system tuning, this turns out not to be the case.

Subsequent to these first notes, I pulled my Quads as far as possible out into the room. "The sonic stage shifted, more depth of image, heightened and supplemented by better lateral image separation. Example, Basia Time and Tide, Epic EK 40767, track 6, "New Day": The envelope of music fills the far end of my room. There is an ability to isolate individual elements within a separate but contiguous sound stage which reaches out to involve me."

As I have learned to do, I walked about, notepad in hand, side to side, speaker to speaker, first back, then forward again. "Ideally, but rarely, the effect is that you can look into the sound stage and see it from different sides. The Atma-Sphere MA-1 has that ability. It's not just that your perspective shifts, but that every element is bolted to the floor and you can move, not the sound stage." In delicate symphonic works such as Grieg's "Morning" from his Peer Gynt, "a harmonious envelope surrounds but separates instruments across the breadth of the stage, the piano possessing and delivering every nuance of tonality. There is a delicate natural mix of harmonic overtones that in some way escapes my "______," a well-respected tube reference amp.

That quality remained as I listened to track 3, Games People Play, "The Best of the Alan Parsons Project," Arista ARC D8193. (I quickly wrote . . . "depth, heightened and supplemented by lateral image separation".) About two minutes into that cut, some background voices emerge and grow with an ambience that seems to fill the spaces in the near field. I went back several times to confirm the effect of that significant 60 seconds. It was subtle but it was there. Imagine that the instruments in front of the soundstage hold the threads of the composition and that they remain in position as the voices move forward and join an ambient envelope, enwrapping the whole sound field.

I could go on and on, but if I haven't as yet convinced you of the amp's uncanny ability to unravel complex harmonic structure and place it on an expansive and realistic stage, then you will need to hear it for yourself.


This past summer I was fortunate enough to attend many live performances. I think the highlight was at Ozawa Hall at Tanglewood. The violinist Kyung-Wha Chung played "Meditation from Thais" by Massenet for her encore. At the conclusion, after the chills and goose bumps passed, I was somehow transformed. I sat second row center, looking up at the performers and thinking this did not sound like a typical stereo system.

"O.K., Ronnie," you're saying, "Duh! It wasn't a stereo system." But the point I am trying to make is that the high-end has moved too far toward ultra resolution, following some insane Pied Piper who plays tunes of DVD and SACD technology. Live, as at Tanglewood, I do not hear razor sharp transients, there are no overlapping, intermodulating harmonic envelopes, and no pants- flapping bass as comes from subwoofers bigger than refrigerators.

Very recently I sat listening to a wonderful $100,000 system comprising two eight-foot towers and eight 18-inch subwoofers. The piano I listened to on this system did not sound like my fond recollections of the piano which accompanied Kyung-Wha Chung at Tanglewood. I believe, that without realizing it, all listening to that expensive system were unconsciously just sitting there and listening around the imperfections and filling in the blanks. To be fair, this highly dynamic, ultra-revealing system was just passing along all the digi-bits that were on the disc, the majority of which had no soul. The Atma-Sphere MA-1 amplifiers are not in that camp. As a matter of fact, they don't sound exactly like S.E.T. amps or my three other amps which are a vintage tube ultra linear, a tube-Mosfet hybrid, and a muscular Mosfet power pumper. Ralph Karsten's OTL amps seem to me to have a unique sound of their own. I think you will agree.

All of this only serves to remind me of the thin line we all walk in our search to fill our souls with music. Straight out of the box, you could not take the measure of how musical these instruments from Atma-Sphere are. As a matter of fact, even after some fairly extended listening, an audiophile seasoned in the ways of things might pass them by. So at the very beginning, it will surely take the care of a tube lover's touch to appreciate their virtues. For these are not beginners‘ toys. You will most probably need to reimage your system and try various speaker cable and interconnect combinations. Integrating the bass portion will be the most problematic part. Using the Argent Room Lenses room correctors made the process a lot simpler for me.

Of course, if you have a room larger than my 12 by 23-foot rectangle, then things could well get a lot easier for you. Strange but true, in my system, I got satisfactory results crossing the bass over at 120 Hz to biamp the low end with a Hafler 500 Mosfet amplifier. Or I could cut it off entirely. Oddly, doing either of these two things only serves to increase your appreciation for the midrange and treble purity. The bottom line, at $8,000, these amps are not cheap. However, truth does not come cheap, so you value musical verity, you truly need not look further.

If you find in tubes the subtle overtones of music, if you value an effortless presentation of voicing, pitch, timbre and timing kept separate on an expansive sound stage, if like me you heed the advice of the Zen master that "The path to enlightenment is defined by minute changes in the sonic fabric," if recorded music occasionally slips the bonds of artifact and seems real and appears before you, then you already know the MA-1.

If not, then you know you have strayed from the path.


Finally, the long upward climb brings me back once again to the cool darkened interior of the monastery. The old one, although blind, has long since known of my return, having heard my footsteps from afar. Wordlessly, I sit facing him and wait.

Finally, in a faint whisper he asks, "So, Grasshopper, what have you learned?"

"Master, I have found music to be an ephemeral fabric layered over a pool of silence. Its existence is fragile. It exists in our hearts or not at all."

Imperceptibly he nods and whispers, "It is well."

Atma-Sphere MA-1 MKII Monoblock Amplifiers, $7,995.00 per pair. Atma-Sphere Music Systems, Inc., 160 So. Wheeler, St. Paul, MN 55105; phone 651/690- 2246, fax 651/699-1175, e-mail ralph@atma-, website

Associated Equipment:

SOTA Sapphire II with electronics flywheel and custom high-current power supply; Grado Signature tonearm; Sumiko Bluepoint Special and Monster Alpha One moving-coil cartridges; SOTA clamp and acrylic mat; Adcom GFT-1A tuner; BIC fm antenna; Magnavox CDB-624 CD player (digital output); Sonic Frontiers Ultra Jitterbug; Assemblage DAC-2 processor; Audio Research SP-9 Mk III preamp; Audio Research Classic 60, Hafler 500, and Heathkit WM-5power amplifiers; Quad ESL-63 speakers with Crosby grilles and Gradient SW-63 subwoofers; Arcici Deadhead turntable stand with Airhead isolation platform; VPI 16.5 record cleaner; Radio Shack SPL meter; Esoteric Ultra Path cables; Monster M1000 II and Audio Research Litzline interconnects; Islatrol a.c. line filter, VPI bricks, and Argent Room Lenses.

Reprinted with permission.
The Audiophile Voice.
P.O. Box 43537
Upper Montclair, NJ 07043