Atma-Sphere MA-3

The Best Audio Amplifier in the World. The most powerful OTL amplifier ever built!

The MA-3 is the culmination of a massive project we began in 1998 at the behest of one of our customers. It was 7 years in design, with 15 different chassis and 12 different circuit concept explorations. The goal: to build the largest OTL amplifier the world has ever seen, while at the same time retaining the qualities our amps have made famous. The end result is arguably the the best amplifier in the world!

There is clearly a need for such an amplifier that can make serious power while being completely transparent and musical; fortunately our OTL technology is well-suited to the task. Since we are not limited by issues that plague conventional amplifier designs, the MA-3 retains a wide bandwidth and low distortion simultaneouly. No transformer-coupled amplifier can produce 200, yet alone 400 watts and get it right at every audio frequency; yet the MA-3 makes 500 watts easily, without electronic artifacts. It’s high-power amplifier that is fast and truly musical!

The MA-3 has all of the features as our other models, plus a few not seen in any other amplifier ever produced. It is class A, all-triode, and fully differential, with our patented direct-coupled output circuit and patented automatic bias control. There is only a single gain stage in the amp, so the signal path is very direct – something unknown in amps of this class. And with all it’s customised components, including custom precision Caddock resistors and tailor-made filter capacitors, it is one of a kind inside and out. The overall output power of the MA-3 can be varied by turning on or off banks of output tubes; the amp can operate on 1/3, 2/3, or all of the output tubes. This makes the amp very easy to live with! Of course, even at lower power levels, the MA-3 retains the innate authority and musical character that defines it as state-of-the-art.

Furthermore, the MA-3’s power supply has a built-in AC line processor that regulates the line voltage coming into the amp! As a result, line voltage has no effect on the MA-3; it will make full power even if the AC line level has dropped to only 100 Volts.

We included a very easy to use built-in tube tester (which can be used at any time the amp is on), allowing one to test the output tubes ‘on-the-fly’ in a matter of seconds. Bias and DC offset functions are automated, using an Atma-Sphere-patented method, with meters to monitor the tubes, output power, line voltage and other features.


Output power

500 watts per channel, 2-16Ω load before clipping


Input Impedance: 100 KΩ single-ended, 200 KΩ balanced
selectable to 600 ohms


2.5 V sensitivity,
RCA and XLR true balanced differential input

Tube complement

42 x 6AS7G output tube ( per channel )
12 x 6SN7 driver tube ( per channel )

Power Storage Capacity

1/4 Farad per channel (more than any production amplifier)

Power Bandwidth

1Hz-100KHz within ½ dB

Frequency response

(1 watt, open loop) 20 Hz squarewave Tilt, unmeasureable
even at full power. 1Hz-200KHz within 0.5 dB

Output section risetime

600 V/µs


Total Harmonic Distortion (THD) typically 0.5% at full power
Intermodulation (IM) distortion typically under 0.004% at full power

Power Supply Weight

152 lbs ( 68.9 kg ) per chassis

Power Supply Dimensions

34″ deep x 21″ wide x 12.5″ tall (86 x 53 x 32 cm) per chassis

Amplifier Weight

80 lbs (36.3 kg) per chassis

Amplifier Dimensions

31.5″ deep x 21″ wide x 15″ tall (80 x 53 x 38 cm) per chassis

Panel Meter Functions

VU level
Individual tube condition
Tube Bias status
DC Offset status
AC line voltage
AC line regulator voltage