Powerful OTL amplifier, 2 x 220 watt monoblocks, 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. 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
- Dual-mono chassis construction
- Automatic bias - no adjustment needed
- Built in VU meter for tube and output monitoring
- Copper foil V-Cap Teflon coupling caps
- Standby switch for long output tube life
- Dual AC power circuits for each chassis
- Uses only one gain stage for supreme 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
- Uses octal-based triode tubes
220 watts per channel into 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)
Selectable up to 600 Ω; 2.8 V sensitivity
RCA and XLR true balanced input
20 x 6AS7G output tube ( per channel )
6 x 6SN7 driver tube ( per channel )
26 dB (for 8 Ω)
2Hz-150KHz within 1/2 dB
( 1 watt, open loop ) 20 Hz squarewave Tilt; unmeasureable, 1Hz-200KHz within 3 dB
Power supply storage
1200 Joules in output section (per channel)
100 Joules in Driver supply (per channel)
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
Power Supply Current
800 watts ( per channel )
28" deep x 17" wide x 10" tall ( 71 x 43 x 25 cm ) per chassis
103 lbs ( 46.7 kg ), per chassis, without tubes
Three year general coverage
One year for output tubes
Brushed black (Anodized)
Brushed silver (Anodized)
Brushed gold (Anodized)
Custom finishes available
Jumper plugs for high efficiency speakers - Replaces tube in the voltage amplifier section of Atma-Sphere
power amplifiers, thus reducing gain for high efficiency speakers. Recommended when efficiency of speaker is over 100.