Atma-Sphere - MP-1 Mk. 3.3


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MP-1 Mk. 3.3

Music Preamplifier


Features :

In 1989, the first MP-1 introduced balanced line technology to the world of high end audio. It was the first balanced, fully-differential preamp ever made, and it included a range of innovations that were breakthroughs at the time, and remain so today. With a history of years of refinement, patents, and awards, the MP-1 is a paragon of the audio world.

The MP-1 Mk. 3.3 is unique in the world of preamplifiers. It easily outperforms any passive or transformer volume control as well as conventional line stages. This is because of a patented circuit that prevents coloration from interconnect cables. And with only three stages of gain in the entire preamp (including the phono section), our Balanced Differential Design® not only assures an elegant signal path, it assure low distortion, wide bandwidth, and dynamic range. No matter what you thought was the best, the MP-1 is an audible improvement.

Our unique, patented circuitry solves a major preamp problem: the output coupling capacitor. This capacitor has to be large to play bass, but large capacitors can't play the mids and highs properly. Getting rid of it is a transparency and bandwidth 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. The MP-1 and the MP-3 stand alone in the world of active preamps that work!

The Balanced Line system was created to eliminate interconnect cable coloration, which is why the recording and broadcast industry has used it for the last 50 years. This is how high fidelity recordings existed before exotic (high end audio) cables existed. The balanced line system is better as it resists RF, hum, noise, cable artifacts (sound changes with different cables) and cable length. This eliminates the need for an exotic cable (and its cost) to achieve state of the art performance.

The MP-1 nicely complements our balanced-line amplifiers, but works well with any amplifier. Phono cartridges are naturally balanced sources; since audio is recorded in the balanced domain, it only stands to reason that you should play it back that way, too. The MP-1 works well with very low output moving coil cartridges (less than 0.2mV), and even doubles as a state of the art headphone power amplifier.

Now for the Mk3.3 improvements! The phono section of the new preamp has more gain and is significantly lower noise than any prior version. In fact it's so quiet that the only way we could achieve the same numbers before was with a Low Output Moving Coil step-up transformer. There is so much more output that the phono is usually at about the same level as many digital sources. The line section is now lower distortion and also has a new shunt-style Gain Trim system that allows for greater control of the gain of the line stage, so high output digital sources are no longer an issue.

  • Balanced Differential Design®
  • XLR connectors for phono and aux
  • XLR output connections
  • Patented direct-coupled Circlotronic® output
  • Fully regulated supplies featuring proprietory circuitry
  • Zero feedback design
  • 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
  • Low-noise "star" grounding topology
  • Power supply isolated in seconds chassis
  • headphone compatible with a simple connector
  • Three-year general coverage warranty with one year warranty on output tubes

Specifications :

Line stage frequency response

.1 Hz - 400 KHz, +0 dB, -3dB ( -0.5 dB @ 250 KHz )

Line stage gain

14 dB

Line stage input impedance

100 K Ω single-ended / 200 K Ω balanced

Line stage output

32 V into 600 Ω

Output impedance

30 Ω

Phono stage input impedance

47 K Ω, adjustable with rear panel loading strip

Phono stage Input Overload

300 mV

Phono stage Max Output

( at clipping ) 120 V peak-to-peak

Phono gain

~66 dB

Phono bandwidth

.5 Hz - 100 KHz, -.5 dB

RIAA accuracy

Within .07 dB

RIAA Phono sensitivity

( for 0.5 V @ 1 KHz ) 0.15 mV

Power Supply storage

170 Joules

Tube complement

8 x 12AT7
10 x 6SN7


( per chassis ) 13" deep x 17" wide x 5.5" tall ( 33 x 43 x 14 cm )

Faceplate dimensions

( standard 3U rack, sans mounts ) 19" wide x 6" tall ( 48 x 15 cm )


( per chassis ) 42 lbs. (19 Kg)