Atma-Sphere S-30 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 the larger amps in the Atma-Sphere line-up, the S-30 represents the high-water mark of compact OTL design.

For audiophiles who seek the ultimate in amplifier design and are realistic about their budget, the S-30 gives you the same precision and sound quality that Atma-Sphere is known and recognized for. Featuring automatic bias and a large VU meter, operation is elegantly simple.

Since the S-30 utilizes patented handwired circuitry proven over three decades, it is stable with any load and both performs and sounds better than any single-ended amplifier ever produced, let alone conventional push-pull designs. Its fully-balanced design and proven class-A triode operation make the S-30 the ideal choice for the discriminating audiophile. Design features of the S-30 Mk. III.2 include:

  • 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


Output Power: 30 watts per channel into 8 Ω load, 45 watts per channel into 16 Ω load.


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

Input: 3V sensitivity (RCA and XLR true balanced input).

Tube Complement: 10 x 6AS7G output tube, 6 x 6SN7 driver tube.

Gain: 23dB (for 8 Ω).

Power Bandwidth: 2Hz-75KHz within ½ dB.

Frequency Response (1 watt, open loop):

  • 20 Hz squarewave Tilt; unmeasurable.
  • 1Hz-200KHz within 3 dB.


  • 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.

Feedback: 2 dB.

Power Consumption: 400 watts.

Dimensions: 13" deep x 17" wide x 8" tall (33 x 43 x 20 cm).

Weight: 24 lbs (10.9 kg) without tubes.

Warranty: 3 year general coverage, 1 year for output tubes.



Optional Features

  • V-Cap Copper Foil Teflon® coupling caps: $600
  • Power supply boost: $450
  • Caddock® resistor upgrade: $1270