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Atma-Sphere Music Preamplifier MP-1 Mk. 3.1

Golden Ear Award                 Reviewer's Choice
     Golden Ear Award                Reviewer's Choice                               

The MP-1 Mk.3.1 is transformation in the world of preamplifiers. It completely outperforms all passive volume controls, transformer volume controls (TVCs) and conventional line stages. Atma-Sphere controls two patents which allow for a breakthrough in this area: no matter what type of preamplifier or volume control system you thought was the best in the past, the MP-1 an easily audible improvement: transformation.

The patented output of the MP-1 is so gutsy that it works as a state of the art headphone power amplifier.

The first MP-1 was built in 1989 and introduced balanced line technology to the world of high end audio. It was the first all-tube preamplifier to offer an all-differential zero feedback package with a direct-coupled high current output capable of driving 600 ohm balanced lines. Even 200 foot interconnects are no problem! Back then it was breakthrough technology, and remains so today, as the MP-1 Mk.3.1 has years of refinement, patents and awards in support of its being the State of the Art preamplifier (many preamps are more expensive, but none sound better). Our Circlotronic® technology has transparency unimaginable to those who have not heard it. Its direct-coupled output solves a major tube preamp problem: the output coupling capacitor. This capacitor has to be large enough to play bass, but large capacitors of any type can't play the mids and highs so well. Getting rid of it is a breakthrough. Transistor preamps often use direct-coupling, but: they sound like transistors! Thus a lot of audiophiles have gone to using passive devices, thinking they have found the answer. This is only because they have not heard technology that works, and frankly, no-one could blame them since the MP-1 (and the MP-3) stand alone in the world of active preamps that work!. If you are not running an MP-1 or MP-3, passive controls may well be the next, albeit distant, best choice.

The MP-1 complements the design of our balanced-line amplifiers and works well with any amplifier with balanced inputs. Phono cartridges are naturally balanced sources; the MP-1 complements them as well. Audio is recorded in the balanced domain- now you can play it back that way too.

Balanced lines have been in use in the recording and broadcast industry for decades to eliminate interconnect cable issues. This is how high fidelity recordings existed before the exotic interconnect cable industry did (the high-end audio industry sort of re-invented the wheel, not knowing what was already out there...). The balanced line system is better because it is resistant to RF, hum, noise and cable differences. Long cables are easy too. This virtually eliminates the need for an exotic cable to achieve state of the art performance.

The MP-1's capabilities, due to its patented direct-coupled output in an all-tube package, is unique. Our Balanced Differential Design® insures a minimal number of gain stages (three from phono input to high level output), low distortion, wide bandwidth and dynamic range: the State of the Art in preamplifiers.

"...the MP-1's ability to bring me closer to the original musical event was head and shoulders above that of any preamp I've ever heard in my home system...I've always felt that the highest praise a reviewer can bestow upon a product are the three little words, "I'm buying it." ...What more can I say? Yes, I'm buying it." -Steven Stone, STEREOPHILE, Dec.'93, Vol.16 No.12

"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, Soundstage!


  • Balanced Differential Design®
  • headphone compatible with a simple connector
  • XLR connectors for phono and aux
  • XLR output connections
  • Patented direct-coupled Circlotronic® output
  • Fully regulated supplies featuring our proprietory regulator
  • Zero feedback design throughout
  • Dual-mono construction
  • Differential passive phono equalization
  • Precision 24 position stepped volume control built from a Shallco® custom switch
  • Two tape monitors (tape functions use RCA's)
  • Precision components used throughout
  • Total system phase switch
  • Teflon® custom coupling caps
  • "Star" grounding used throughout
  • Outboard power supply
  • Two-tone antique finish
  • Three-year warranty


  • V-CAP Teflon coupling caps for phono $500 (replaces a set of polystyrene parts in the output of the phono section)
  • V-CAP Teflon caps throughout (includes the phono location above) $1500
  • Caddock resistor package $1700
  • Caddock volume control $2600
  • Low output MC stepup transformers (not recommended unless cartidge is 0.2mV or less) $750
  • Damping package $600
  • Dual outputs $75.00
  • alternate panel finishes available


  • Line stage bandwidth: .1 Hz - 400 kHz, +0 db, -3db (-0.5db @ 250KHz)
  • Line stage gain 14 db
  • Line stage input impedance 500K single-ended / 1M balanced
  • Line stage output 32 V into 600 ohms
  • Phono gain: ~60db
  • Phono bandwidth: .5 Hz - 100 kHz, -.5 db
  • Phono input impedance 47K- easily set with rear panel loading strip
  • RIAA accuracy: within .07 db
  • RIAA phono sensitivity: 0.15 mV
  • Phono section max output: 120 V p-p
  • Phono input overload: 250 mV
  • Power supply storage: 170 Joules
  • Tube complement: 8 12AT7s, 10 6SN7s
  • Dimensions: 17" Wide (19" panel width), ~12.5" Deep, ~6" High, 2 chassis
  • Weight ~45 lbs.

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