MP-1 Mk. 3.3
music preamplifier 
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, with innovations that were breakthroughs at the time and remain so today. With decades of refinement, patents and awards, the MP-1 is a paragon of the audio world.

The Mk. 3.3 update has affected the MP-1 more than than the rest of our lineup. More about that later... if the MP-1 is something you've not encountered before, it is unique in the world of preamplifiers. It easily outperforms conventional line stages and any passive or transformer volume control on account of its patented direct-coupled output which allows for greater transparency while also preventing coloration from interconnect cables. With only three stages of gain in the entire preamp (including the phono section), our Balanced Differential Design® is an elegant signal path that assures low distortion, wide bandwidth and dynamic range. No matter what you thought was the best, the MP-1 is an audible improvement.

Our patent solves a major preamp problem: the output coupling capacitor of the preamp. This capacitor has to be large to play bass (especially driving solid state amps), but large capacitors can't play the mids and highs properly no matter how good the capacitor is. Getting rid of it is a transparency and bandwidth breakthrough. Until we created our patent, there really was no way to do this reliably with vacuum tubes. Transistor preamps often use direct-coupling, but sound like transistors! Some 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 MP-1 is fully differential and balanced because the Balanced Line system eliminates interconnect cable coloration, which is why the recording and broadcast industry has used it for the last 55 years. This is why high fidelity recordings existed before exotic (high end audio) cables did! The balanced line system is better as it resists interference and noise, as well as 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, now you can play it back that way, too; this elimintates the artifact of the tone arm interconnect cable. The MP-1 works well with very low output moving coil cartridges (less than 0.2mV) and is 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®
  • Supports the Balanced Line standard (AES48)
  • Robust output that can drive 32 ohm headphones
  • XLR connectors for phono and aux (paralleled RCA inputs optional)
  • Dual XLR output connections (RCA outputs optional)
  • Patented direct-coupled Circlotronic® output
  • Fully regulated supplies
  • 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 seperate chassis
  • headphone compatible with a simple connector
  • optional RCA input and output connections available
  • other options: click on 'Order' above
  • Three-year general coverage warranty with one year warranty on output tubes

Line stage frequency response

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

Line stage gain

12 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

10 x 12AT7 (phono section)
6 x 6SN7 (line section)


( 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)


Three year, transferable
One year for tubes
For all support requests or any questions about your Atma-Sphere product, contact us directly at (651) 690-2246 or send us an email.
Available with both phono and line stage, or line stage only.

Optional Features

Remote Volume Control
V-CAP Copper foil capacitors for line stage
V-CAP Copper foil capacitors throughout
Caddock resistor package
Caddock volume control
Dual phono inputs available
Low output Moving-Coil step-up transformers
      for cartridges under 0.2 mV
Damping package
Switchable Tape head input (and EQ)

Front Panel finish options

Brushed Gold (Anodized)
Custom panel finishes available upon request


Balanced to Unbalanced adapter: $60.00/pair
      For use with single-ended amplifiers or sources. Specify input or output.


Balanced Interconnects
Balanced phono cables
      1 meter, DIN to XLR or RCA with ground post to XLR


Contact your local dealer for pricing information.
Or, call (651) 690-2246 or email us with any questions.