June 2002

Atma-Sphere MP-3 Preamplifier

by Ken Micallef

In the world of output-transformer-less power amps, Atma-Sphere Music Systems of St. Paul, Minnesota is perhaps the heaviest hitter. But Atma-Sphere's two preamps -- the single-chassis MP-3 ($3300 USD for a straight line stage, $3800 including phono stage) and the pricey two-box MP-1 Mk II ($7695) -- have received less attention. In my opinion, one thing that works against Atma-Sphere preamps is their appearance. As a proud and very satisfied owner of M-60 Mk II.2 amps, I can state that their glowing, exposed 6AS7 tubes are a lust-inspiring sight, but otherwise, the amp’s military-looking rough-cote finish and 1940s battleship functionality are a slight turn-off. This dichotomy reveals how Ralph Karsten of Atma-Sphere allocates his funds: on the circuitry, not the cosmetics.

The MP-3 is a fully differentially balanced design (forget your RCA interconnects) that Karsten claims will easily drive a 200-foot pair of interconnects. The face of the MP-3 looks like the control panel of a B-1 bomber -- no rounded sleek edges or fancy trim here, bubby. Five toggle switches handle source selection, tape loops and inversion of phase, while a separate toggle on the far right is the on/off switch. Down the center of the unit is a trio of small LEDs, indicating power on and DC offset bias for each channel. A large stepped volume-control knob is bordered by two small gain-control knobs, which Karsten recommends you leave dialed to full tilt after the initial break-in period and warm up of the preamp. Now, I personally found the large volume-control knob to feel very clunky, and its three-tiered design is sort of like a lopsided pyramid. I could never figure out exactly where the knob was pointing at any given moment. Do I have it turned all the way down or to the midway point? It wasn’t difficult to set the MP-3 to a desired volume level, but in general, those stepped volume knobs feel to me like the controls on a tube tester, not a high-end-audio rig. Call me persnickety. Anyway, the gain controls are used to balance sections of the line section’s 12AU7 tubes, which are not in the signal path. After the P-3's burn-in period, it was set the gain controls and forget about it.

Lifting the hood off the MP-3 chassis, I noticed ample amounts of stiff blue material affixed to the cabinet's sides and the inner surface of the lid, no doubt some space-age damping substance. Not an entirely point-to-point-wired affair like some manufacturers espouse, the MP-3 uses a printed circuit board chock full of quality components. To the left are seven 12AT7 tubes for the phono stage, to the right a pair of 6SN7s and a pair of 12AU7s for the line stage. Atma-Sphere’s own yellow capacitors populate the circuit board, along with various Japanese jobbies, a hefty-looking side-mounted transformer and two smaller flat-mounted ones as well. Ample hard wiring is evident throughout the unit, from the front controls to the large balanced input connectors to the main outs and tape-loop RCAs.

The MP-3 has undergone some changes over time, which Ralph Karsten explained:

The MP-3 uses three power transformers. We made improvements in all three. This allowed for reduced noise in the filament supplies. The result was a more lively sound and less noise. We also lowered noise in the phono section by improving RF rejection. Two of the power transformers are used in the patented output section -- we boosted the voltage a bit which increased dynamic range and improved "punch." Finally, we switched from the Russian 6SN7s to the Chinese version, which is a considerably better tube (although many of our customers order hand-picked NOS tubes for the unit anyway). Older MP-3 preamps can all be updated to the latest version. We reactivate the warranty whenever we update one of our products to the latest level, which helps protect the customer against obsolescence.

The cost of the upgrades is "about $250" and depends on the vintage of the particular MP-3. The unit I had for review was fully upgraded and up to date.

Review system

I was very curious to see how the MP-3 would stack up next to my modified Blue Circle BC21/BCG21 preamp. Bear in mind, the stock BC21 costs $1500, the BCG21 power supply upgrade raises the cost to approximately $3000, and I paid dearly for additional Black Gate capacitors and tube rectification. The rest of my rig includes the M-60s Mk.II.2s (with latest upgrades), a Bel Canto eVo 200.4 power amp, Revel Performa M20 and Audio Physic Virgo speakers, Acoustic Zen Silver Reference (CD player to preamp) and Cardas Golden Reference (preamp to power amp) interconnects, and Acoustic Zen Satori speaker cables. Shunyata King Cobra and Black Mamba with JPS Labs Power AC and Kaptovator power cords run from a Shunyata Hydra, while CD duties are currently in flux, running out of a borrowed Electrocompaniet EMC-1 CD player or a Pioneer DV-525 DVD player with a Monarchy 22C DAC. To test the MP-3's phono stage, I used my Oracle Alexandra turntable with Grado Platinum Reference cartridge sitting atop a Symposium shelf.

Shimmy, shimmy coco-bop

Dropping Pat Metheny Group’s latest Speaking of Now [Warner Bros. 48025-2] into the Pioneer DVD player and pushing its plastic play button, the first thing I noticed was how big, rich and warm the sound was from the MP-3. The soundstage was simply huge, front to back, top to bottom. The music was also noticeably relaxed, even laid-back, especially in comparison to the presentation of the Blue Circle preamp. The MP-3 demonstrated a certain rightness and accuracy of tone and presentation along with a big, bold quality similar to that of the 47 Labs Flatfish transport and Progression DAC -- an unequal comparison, but high praise indeed in my book. Just as the 47 Labs duo (with power supply) exhibited a big hearted and naturally organic soulfulness, so did the MP-3. Perhaps a little dark, the overall sound was one of great relaxation and depth. Instead of focusing on single traits that jumped out at me, the MP-3 seemed to breathe a sigh of relief over my rig, allowing it to simply make music without any fussiness or explicit focus on certain aspects of the musical spectrum.

The Metheny disc, as with his prior efforts, is pretty lush-sounding on its own, with acoustic drums and bass, voices and acoustic piano surrounding Metheny’s often chorus-laden electric guitars, producing a kind of romantic and natural rainforest tableau. If I chose to focus on individual sounds like Antonio Sanchez’s drums, doing so was also very pleasurable and effortless. Image specificity was a forte of the MP-3, but only if you choose to listen that way. I could easily pick out every little cymbal splash, across-the-stereo-mix tom-tom roll and gritty snare-drum articulation. And again, there was great body and depth for individual sound sources. While cymbal decay was as deep and as lengthy as I have ever heard, bass-drum notes were tight, tuneful and extended. Steve Rodby’s acoustic bass notes were also very well defined, deep and liquid.

High Contrast is a 22-year-old drum-and-bass artist from Brighton, England who is reinventing the '90s dance genre with a fresh sample approach, which includes natural drum sounds, oceanic ambience, and sampled insanity. His True Colors [Breakbeat Science 5] also features a broader sonic punch than many one-dimensional dance recordings. Here, programmed synth and cymbals were smooth and very articulate, but still relaxed. Synth bass and sampled bass drum were low, deep and powerful -- I could feel it in the floor as I walked around my apartment! Another track begins with a lone female voice breathing deeply in and out followed by the full assault of Rhodes piano, warbling "darkstep" bass, and hyperspeed drumming. The MP-3 handled the sound-clash with ease and rendered the slightly distorted quality of the bass drum with spot-on accuracy. The MP-3 made music of the dense, forward production, layering all the unnatural electronic sounds of this big dance mix with extreme clarity and extreme musicality.

The MP-3 also has a unique way of floating piano, guitar, brass and string notes right in front of you in an almost surreal way. The sounds were not disconnected; they just became more evident and liquid. Perhaps this is due to the recording, but it is a surprising trait nonetheless. It was apparent on almost every recording I played, so for a different flavor I popped in the excellent orchestral CD Previn Conducts Korngold: The Sea Hawk [Deutsche Grammophon 289 471 347-2]. This CD includes music from the films The Sea Hawk, The Private Lives of Elizabeth and Essex, Captain Blood and The Prince and the Pauper. The Sea Hawk is particularly full-bodied, with soaring climaxes and romantic interludes. I cranked the volume and gloried in the full-throated roar of the orchestra and its wealth of instruments. Again, the MP-3 made great music. I noted the fleshed-out, full orchestra to the back of the hall, and all the ambient cues were well presented. Crescendos were sufficiently breathtaking, blowing through my house like a tornado. At times, I felt like I was sitting a movie theater, lights darkened, with the sound pouring over me from all angles. My small room does not allow for much "beyond the speakers" imaging, but with the MP-3 on board, the music was certainly as deep and broad as I have ever heard it.

Unfortunately, I could only hear the MP-3 with the Atma-Sphere M-60 Mk II.2s for a brief time, as I sent the amps off for repair (burned resistors) and upgrade (additional circuit with extra 6SN7 tube) shortly after the preamp’s arrival. But when I did couple the trio of MP-3 and M-60 Mk II.2s, it was obvious that there was some special synergistic magic happening here. The MP-3 bettered the BC21 with power-supply upgrade in every aspect here, sounding bigger, bolder, more natural and extended across the board. My audio friend, Minister Yagerman, listened up and said "No contest, my son." How can you argue with a man of the cloth? The MP-3 was as striking with the Bel Canto eVo 2004, but the synergy thing was not happening in the same way. It excelled in every way I have previously described, but there was greater variance.

Many audiophiles (including Ralph Karsten, who graciously sent me a pair of RCA-to-balanced interconnects) praise the phono stage of the MP-3, so I fired up my analog setup to hear what the fuss was all about. Dusting off the Dirty Harry Anthology conducted by Lalo Shifirin [Aleph Records/Simply Vinyl SVLP 082], I dropped the needle on "Dirty Harry’s Creed," which features the famous "Well, do you, punk?!" line, followed by a thunderous drum line, bubbling tablas, Rhodes piano, electric bass, and ominous strings. Compared with the same CD, the MP-3's phono stage created much more air, greater presence, with bass very up front and in my face. On climaxes, I could detect the drums echoing off the studio walls, the MP-3 making everything clear and smooth throughout every frequency range. Bass sounded especially resonant and metallic, coiling through the mix just the way I imagine it sounded in the studio. More refined and less imposing than with CD, the sound was neutral. With an outboard EAR 834P (connected by an Acoustic Zen Matrix reference IC), the sound was fatter, broader and more resonant, but lacked the grace and refinement of the MP-3's presentation. The bass was more extended, but also more loose. It was also deeper, but slightly more ragged. Sounds were just as big and bold though, perhaps more so, and as dynamic and punchy.

Comparison

I have been using a Blue Circle BC21 preamp with BCG21 upgraded power supply (in a separate chassis) for some time now, and I recently went a step further and had most of the BC21's capacitors changed out for Black Gates, and the separate power supply upgraded with tube rectification via a 5AR4 tube. For my money, both of these changes made the BC21 much more dynamic and transparent, moving the listener from seventh row with a little grain, to second row looking right in the performer’s nostrils. I personally love this in-your-face presentation, but for some it may be a tad relentless. The Black Gates only slightly improved the low end wallop of the BC21, which with the double whammy of the power supply upgrade, is already a very punchy and tight performer. Transient speed did improve, due to the Black Gates and the tube rectification I believe.

I have owned and reviewed preamps by Muse, Audio Note, Legend Audio, Placette, and others, but none of these have sounded as natural, larger than life and butt slamming as the MP-3. In some ways, the BC21/BCG21 with upgrades is more transparent in an absolute sense, and perhaps imposes less of an overall personality of its own on the music. I could hear more drastic changes when switching out other components when the Blue Circle preamp was in the system. It seemed to almost disappear more completely. It just doesn’t impress an extroverted personality on the music as does the MP-3. The Blue Circle doesn’t make its presence as known. But for sheer enjoyment, the MP-3's massive sound, which is very detailed, full of power and attitude, yet delivered with great ease and a certain resonant rightness of tonality, is hard to beat.

Conclusion

The Atma-Sphere MP-3 preamplifier conducts music with a bold, generous, daring character. It is truly a magnanimous performer, with the ability to wrench fine detail from source material, and with great attention to purity of tone, clarity, and focus. Recording after recording, I was taken with the MP-3's ability to fill the listening room with not only fireworks and bold hues in a Technicolor soundstage, but also fine detail. With LPs, the MP-3 was more accurate, exposing less of its own personality and lending great transparency to each recording.

Not the most attractive tube preamplifier around, the MP-3 is certainly one of the best I've heard.

...Ken Micallef
ken@soundstage.com

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