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Atma Sphere S-30

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

Atma Sphere S-30 hi-end valve amplifier

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. 

Because it utilises decades-proven patented handwired circuitry, 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.


- 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

Atma Sphere S-30


Reviews and Awards

Revue Du Son Et Du Home Cinema
Jean Hiraga & Robert Lacrampe, Oct. 2002
Page 1Page 2Page 3
Various, user submitted 

Extreme AV
Vangelis Lazarou (in greek) 
Page 1Page 2Page 3Page 4

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 

2 dB

Power consumption
400 watts

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

Gray hammertone
Brushed anodized black
Brushed anodized silver
Brushed anodized gold
Custom finishes available upon request


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 

For additional informations, audition and pricing, contact our worldwide dealers, or our headquarters.


Atma Sphere
1742 Selby Avenue
St. Paul, MN 55104


Tel : +1 651-690-2246