Atma-Sphere M-60

Hi-End Audio Tube Amplifiers, 2 x 60 Watts, OTL monoblocs, Mk 3.3

For years now the M-60 in its various forms has been the subject of the Soundstage! Hall of Fame Award, The Absolute Sound Golden Ear Award and Editor’s Choice, with numerous accolades in the press and on the web.

The M-60 Mk. 3.3 continues that tradition with classic styling and its award-winning state-of-the-art performance. The M-60 gives you the features and precision performance of our larger models in a beautiful, 60-watt package. The amp operates class A and is unconditionally stable with reliability proven over many years.

The power tubes are inexpensive, readily available and do not require any matching. Sporting a classic, open-chassis construction, the M-60 Mk. 3.3 sets the bar for hi-end amplifier performance.


– Balanced Differential Design®
– Class-A2 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
– Standby switch for long output tube life

– 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 base triode vacuum tubes
– Classic open chassis construction with Wrinkletex™ finish
– Three-year general coverage warranty, one year warranty on output tubes

Making the M-60

An insight into how we build our award-winning OTL amplifier

The Atma-Sphere M-60 amplifier is handmade with the highest quality components. We offer to our customers the possibility to further customize our products, according to their needs.


Output power

60 watts per channel into 8 Ω load
45 watts per channel into 4 Ω load
80 watts per channel into 16 Ω load


Input Impedance: 100 KΩ single-ended, 200 KΩ balanced
Output Impedance: ~4.1 Ω


3 V sensitivity ( for full output )
RCA and XLR true balanced input

Tube complement

8 x 6AS7G output tube ( per channel )
4 x 6SN7 driver tube ( per channel )


20dB (for 8 Ω)

Power Bandwidth

2Hz-75KHz within ½ dB

Frequency response

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

Power supply storage

140 Joules ( per channel )


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

Output section risetime

600 V/µs


1 dB

Power consumption

300 watts ( per channel )

Dimensions & Weight

13″ deep x 17″ wide x 8″ tall (33 x 43 x 20 cm) per chassis
30 lbs (13.6 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


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 100dB.


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