Atma-Sphere MA-1

The best tube amplifier worldwide, 2 x 140 watts OTL monoblocs, Mk 3.3

Recipient of The Absolute Sound’s prestigious “Golden Ear Award” in 2000, the MA-1 enjoys an enviable reputation. Now the Mk. 3.3 series builds on proven technology. An improved output section and enhanced driver circuit contribute to superior low-level detail, smoother sound, wider bandwidth and AC power immunity. The rugged, non-magnetic chassis features classic looks with superior layout. Setup of the amplifier is simple with it’s automatic biasing system. The controls and switches are ergonomic without sacrificing performance.

The MA-1 is extraordinary in every way. Not only is normal operation easy on the vacuum tubes, the effect of a tube failure on the unit is entirely inconsequential. Despite its extreme performance, the MA-1 is known for remarkable ease of setup, ease of operation, day-to-day consistency and of course extreme musicality.

Featuring our new custom wire, V-Cap Teflon coupling caps, custom resistors, and all the other extras for which we are known, the MA-1 shines as an example of why our amplifiers are the best amplifiers worldwide, regardless of cost.



– 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
– Easily monostrapped for greatly increased power
– 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
– Exclusively uses Octal-Triode based vacuum tubes
– Classic open chassis construction with Wrinkletex™ finish
– Three-year general coverage warranty,
– One year warranty on output tubes




Output power

140 watts per channel into 8 Ω load
135 watts per channel into 4 Ω load


Input Impedance: 100 KΩ single-ended, 200 KΩ balanced
Output Impedance: ~2.3 Ω
(power method standard measurement)


2.8 V sensitivity
RCA and XLR true balanced input

Tube complement

14 x 6AS7G output tube ( per channel )
5 x 6SN7 driver tube ( per channel )


25dB (for 8 Ω)

Power Bandwidth

2Hz-200 KHz within ½ dB

Frequency response

(1 watt, open loop) 20 Hz squarewave Tilt, unmeasureable
1Hz-300KHz within 3 dB

Power supply storage

600 Joules ( per channel )


Total Harmonic Distortion (THD) typically 0.5% at full power.
Intermodulation (IM) distortion typically under .005% at full power.
Phase shift less than 1° @ 20KHz

Output section risetime

600 V/µs

Power consumption

500 watts ( per channel )


18″ deep x 17″ wide x 8.5″ tall ( 46 x 43 x 22 cm)
per chassis


36 lbs. ( 16.3 kg ), per chassis, without tubes


Three year general coverage
One year for output tubes



Power Supply Boost
V-Cap Copper Foil Teflon® coupling caps
Caddock® resistor package

Meter Panel finish options

Brushed anodized silver
Brushed anodized gold
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.


Balanced Interconnects
Balanced phono cables
1 meter, DIN to XLR or RCA with ground post to XLR