Introduced in 1990, the MA-2 was the largest production triode amplifier and the largest production OTL in the world for nearly 12 years. In that time it set the bar for quality that has yet to be surpassed; it is one of the finest amplifiers made anywhere in the world regardless of price. Not only is it one of the most powerful production Output Transformerless amps available, it is also the most reliable. Audio purists have craved the design features of this amplifier since the beginning of Hi-Fi; only Atma-Sphere has succesfully put them all in the same place at the same time.

Now the Mk. 3.3 boasts an improved gain stage with even wider bandwidth and greater transparency than ever before. We have 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. This is an unusual combination but this is what sets Atma-Sphere apart from 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
  • Copper foil V-Cap Teflon coupling caps
  • 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

Impedance

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
2.8 V 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-150KHz within 1/2 dB

Frequency response

( 1 watt, open loop ) 20 Hz squarewave Tilt; unmeasureable
1Hz-200KHz within 3 dB

Distortion

Total Harmonic Distortion ( THD ) typically 0.4% at full power
Intermodulation ( IM ) distortion typically under .04% at full power
Phase shift less than 1 degree @ 20KHz

Output section risetime

600 V/µs

Feedback

2 dB

Power consumption

800 watts/channel

Power Supply Current

80 Amps/channel

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, without tubes ) 103 lbs ( 46.7 kg )

Warranty

Three year general coverage
One year for output tubes