Atma-Sphere Class D GaNFET

Atma-Sphere writes: "The Class D project is something we started in 2017; it was about then that we started hearing class D amps that were demonstrating good potential so we started our own research. 

"Within about 6 months we had a prototype that was showing us that this was worth of pursuit." In 2020 we were granted a patent in the field. We continued our research; our goal was a solid state amp that had all the positive attributes of a good tube amplfier, and since our amps have been getting great reviews and awards in the high end press for the last 30 years or so we felt we were in a good position to know if and when we were achiving this goal. We can safely say we have a solid state amp that has all the smoothness in the mids and highs that you expect from an excellent tube amp, but with considerably lower distortion and dramatically lower output impedance. 

The Class D is based on GaNFET output devices and accepts both single-ended and balanced inputs. The circuit is entirely of our own design and manufacture- it does not use anyone else's modules. Its nice to be able to say that we 'cracked the nut' so to speak in making a solid state amp that actually makes tube amps obsolete; of course that is a very old claim that many have made over the decades; how our claim might be different is that we've spent a considerable amount of time looking into how the ear interacts with distortion. Tube amps generate a fair amount of either 2nd or 3rd harmonic (the latter in the case of our tube amps) which the ear regards as innocuous. Its the higher ordered harmonics and intermodulations that cause an amplifier to sound harsh and bright. Tubes get around this because the 2nd and 3rd can mask those higher ordered harmonics, resulting in smooth sound. The Class D amp has the same kind of distortion signature, but at a much lower level. This allows it to have the same smooth character, but with greater transparency- in direct comparisons its easier to make out details in the rear of the soundstage; its more focused. That and the way it plays bass are the tells that make it different from our tube amps; otherwise it has the same liquid organic mids and highs, the same delicacy for which our tube amps are known. This amp has a very nice first watt!" 


- Balanced input
- GaNFET output transistors
- rugged chassis
- Monoblock
- No adjustments needed

- Exclusive Atma-Sphere class D module
- Precision components used throughout
- Low-noise even on horn speakers
- Over-current protected
- Stable with all input and load conditions
- Classic Wrinkletex™ finish
- Three-year general coverage warranty

Output power

100 watts per channel into 8 Ω load 
200 watts per channel into 4 Ω load
50 watts per channel into 16 Ω load 

Input Impedance

100 KΩ balanced/single-ended

Output Impedance:

~0.010 Ω


2.15 Vrms for full output
RCA and XLR true balanced input



Power Bandwidth


Frequency response



Total Harmonic Distortion (THD) typically 0.1% at full power.
Intermodulation (IM) distortion typically under .04% at full power.


35 dB

Power consumption

5 watts at idle (per channel)

Dimensions & Weight

13" deep x 11" wide x 3" high (33 x 28 x 8 cm) per chassis  
14 lbs (6.35 kg), per chassis 


Three year general coverage