MA-2 Mk 3.3

Introduced in 1990, the MA-2 was the largest production triode amplifier and the largest production OTL in the world for nearly 12 years. Not only is it one of the most powerful production Output Transformerless amps available, it is also one of the most reliable. Though audio purists have craved the design features of this amplifier since the beginning of Hi-Fi, only Atma-Sphere has successfully put them all in the same place at the same time.

Now updated to Mk. III.2, it boasts an improved gain stage with even wider bandwidth and greater transparency than ever before. Additional features include added switchable feedback and automatic tube biasing to round out the package. Yet it remains smooth, detailed, and tuneful with a speed that belies such a large tube amplifier. Unlike many other amplifiers, it will stand up to constant playback without any noticeable artifact. And the improvements the MA-2 offers will be obvious on any system within seconds of powering it up; it sounds that good.

The MA-2 is noted for its superior performance on Sound Lab, Wilson Audio, JM Labs, Magnaplanar and Avalon loudspeakers. These are speakers that need an amplifier capable of serious power. An amplifier that can fully utilise the full bass frequency range of the speaker with the proper control and impact, while simultaneously retaining detail, delicacy, and speed. In any ordinary audio amplifier, this versatility would be unheard of, but in an Atma-sphere amplifier, it's just par for the course; the MA-2 was and is light years ahead of the competition.

  • Balanced Differential Design®
  • Class-A operation
  • Patented Circlotronic® direct-coupled (OTL) output stage
  • Automatic bias, so no adjustment is needed
  • Built in VU meter for tube and output monitoring
  • Easily monostrapped for greatly increased power
  • Standby switch for long output tube life
  • Dual AC power circuits for each chassis
  • Uses only one gain stage for simplicity and clarity of sound
  • Proprietary precision components used throughout
  • Low-noise "star" grounding topology
  • Fully hand-wired point-to-point electronics - no circuit boards!
  • Stable with all input and load conditions
  • Exclusively uses Octal-Triode based vacuum tubes


Output Power: 220 watts per channel into a 4, 8, or 16 Ω load before clipping.


  • Input Impedance: 100 KΩ single-ended, 200 KΩ balanced - selectable to 600 Ω.
  • Output Impedance: ~1.75 Ω (open loop).

Input: Selectable up to 600 Ω, 2.8V sensitivity (RCA and XLR true balanced input).

Tube Complement (per channel): 20 x 6AS7G output tube, 6 x 6SN7 driver tube.

Gain: 26dB (for 8 Ω).

Power Bandwidth: 2Hz-100KHz within ½ dB.

Frequency Response (1 watt, open loop):

  • 20 Hz squarewave Tilt; unmeasurable.
  • 1Hz-200KHz within 3 dB


  • Total Harmonic Distortion (THD) typically 1% at full power.
  • Intermodulation (IM) distortion typically under .04% at full power.
  • Phase shift less than 1° @ 20KHz.

Output Section Risetime: 600 V/µs.

Feedback: 2 dB.

Power Consumption (per channel): 800 watts.

Power Supply Current (per channel): 80 Amps.

Power Supply Storage (per channel): 1200 Joules in output section, 100 Joules in driver supply.

Dimensions (per chassis): 28" deep x 17" wide x 10" tall (71 x 43 x 25 cm).

Weight (per chassis): 103 lbs (46.7 kg) without tubes.

Warranty: 3 year general coverage, 1 year for output tubes.



MA-2 Mk. III.2