Atma-Sphere S-30

High End OTL Tube Amplifier, 2 x 30 Watts, Mk 3.3

The S-30 is the unchallenged state-of-the-art in low power vacuum tube amplifiers. With its simplicity of operation, small footprint, and all the features of our larger amps, the S-30 represents the high-water mark of compact OTL design.

For those who seek the ultimate in amplifier design the S-30 gives you the same precision and sound quality for which Atma-Sphere is known. Featuring automatic bias and a large VU meter, operation is elegantly simple.

The S-30 utilises decades-proven patented handwired circuitry so is stable with any load. It performs and sounds better than any single-ended amplifier; a nice choice for a loudspeaker that does not need high power. Its fully-balanced design and proven class-A triode operation makes the S-30 the ideal choice for the discerning audiophile.


– Balanced Differential Design®
– Class-A2 operation
– Patented Circlotronic® direct-coupled (OTL) output stage
– Dual-mono chassis construction
– Automatic bias
– Built in VU meter for tube and output monitoring
– Uses only one gain stage for supreme clarity of sound

– Precision components used throughout
– Low-noise “star” grounding topology
– No circuit boards- hand wired
– Stable (will not oscillate) with all input and load conditions
– Uses only octal triode vacuum tubes
– Classic open chassis construction with Wrinkletex™ finish
– Three-year general coverage warranty, one year warranty on output tubes


Output power

30 watts per channel into 8 Ω
45 watts per channel into 16 Ω


Input Impedance: 100 KΩ single-ended, 200 KΩ balanced
Output Impedance: 7 Ω


3 V sensitivity
RCA and XLR true balanced input

Tube complement

10 x 6AS7G output tube
6 x 6SN7 driver tube


23dB (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

Hum and noise

Less than -75db below 1 watt,
-95db below full power (30 watts)


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

Power consumption

400 watts


2 dB

Dimensions & Weight

13″ deep x 17″ wide x 8″ tall ( 33 x 43 x 20 cm )
24 lbs ( 10.9 kg ), without tubes


Three year general coverage, one year for output tubes

Optional Features

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

Meter Panel finish options

Black Wrinkle
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 100.


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