MA-3 Mk. 3.1

The MA-3 is the culmination of a massive project Atma-Sphere began in 1998 at the behest of one of their 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.

There is clearly a need for such an amplifier that can make serious power while being completely transparent and musical; fortunately Atma-Sphere OTL technology is well-suited to the task. Since Atma-Sphere is 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 the other models in the lineup, plus a few not seen in any other amplifier ever produced. It is class A, all-triode, and fully differential, with the 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.

Atma-Sphere 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


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


2.5 V sensitivity
RCA and XLR true balanced input

Tube Complement (per channel)

42 x 6AS7G output tube
12 x 6SN7 driver tube


23dB ( for 8 Ω )

Power Bandwidth

2Hz-100KHz within ½ dB

Frequency Response

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


Total Harmonic Distortion ( THD ) typically 0.5% at full power
Intermodulation ( IM ) distortion typically under .004% at full power
Phase shift less than 1° @ 20KHz

Output Section Risetime

600 V/µs

Power Storage Capacity (per channel)

1/4 Farad

Power Supply Weight (per chassis)

152 lbs ( 68.9 kg )

Power Supply Dimensions (per chassis)

34" deep x 21" wide x 12.5" tall (86 x 53 x 32 cm)

Amplifier Weight (per chassis)

80 lbs (36.3 kg)

Amplifier Dimensions (per chassis)

31.5" deep x 21" wide x 15" tall (80 x 53 x 38 cm)

Panel Meter Functions

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


Three year general coverage
One year for output tubes