Atma-Sphere Logo amplifier manufacturer now stocked by HiFi House

Class D Monoblocks

Atma-Spheres Class D project has been in the works since 2017. Accordingly  the goal being to expand on the positive attributes of the existing amplifiers, which have received great reviews and awards in the high end press for the past 30 years.

Finally the result is a solid state amplifier that uniquely has all the smoothness you would notably expect from an excellent valve amp, but equally has considerably lower distortion and output impedance but with higher efficiency.

A mono-block design based on GaNFET output devices, the circuit is entirely Atma-Spheres own design and manufacture. The power supply employs a toroidal power transformer and has over-current protection to keep the amplifier safe in case of a short at the speaker terminals.

Like their other amplifiers, this one certainly has a very nice first watt indeed!

hi-fi+ October 2023 Review

Customer Feedback


Single-ended and True Balanced input
GaNFET output transistors
Rugged chassis
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
Three-year general coverage warranty


Output power: 100 watts per channel into 8 Ω
200 watts per channel into 4 Ω
Input Impedance  100 KΩ balanced/single-ended
Output Impedance: ~0.010 Ω
Input: 2.15 Vrms for full output
Gain 22dB
Total Harmonic Distortion less than 0.1% at full power.
IM distortion less than .04% at full power.

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

Mono-block amplifier running in Class D from Atma-Sphere

£6000.00 (inc VAT) per pair

HiFi House  is delighted to be able to offer our UK customers, the superlative, game-changing Class D Power Amplifier and MP-3 tube Pre-amplifier, both  delivering truly incredible performance. Please Contact Us for further information, to arrange a demonstration or indeed to place an order.

MP-3 is a fully differential all-tube preamplifier - Black or Silver finish

MP-3 Tube Pre-amplifier

The MP-3 is  a single chassis, fully differential all-tube preamplifier with a direct-coupled high current output capable of driving low-impedance balanced cables.

The pre-amplifier perfectly complements the balanced design of the fantastic Class D power amplifier or as a matter of fact any other balanced power amplifier you wish to use.  Patented innovations, developed specifically for this preamplifier, make it certainly one of the best preamps available today.

Its strength being, it extracts more ambient information with greater image specificity, bass definition and dynamic range than any single-ended preamplifier, owing to its patented direct-coupled output.

In addition to its remarkable line level section, the MP-3 works well with low-output moving coil cartridges and uses a  low number of gain stages (only three from phono input to line level output). Insures low distortion, wide bandwidth and superb dynamic range. The result is a truly musical package of exceptional value.

Rear view layout of MP-3 Pre-amplifier from Atma-Sphere

Balanced Differential Design®
XLR connectors for phono and auxiliary inputs (paralleled RCA inputs optional)
Regulated high voltage
Two stage Constant Current Sources for each stage of gain (improves performance of each gain stage)
Dual XLR outputs standard (RCA outputs optional)
Patented direct-coupled Circlotronic® output
Zero feedback design throughout
Balanced differential passive phono equalization
Precision 23 position stepped volume control built with 96 resistors on a custom built switch
Two tape monitor inputs, tape functions use RCA jacks
Precision components used throughout
Total system phase switch
Low-noise “star” grounding topology
Three-year general coverage warranty with one year warranty on output tubes


Line stage frequency response 1 Hz-200 KHz, +0 dB, -2dB
Gain  15 dB
Input impedance 100 Kohm Ω single-ended/200 Kohm Ω balanced
Output 12V
Output impedance 250 Ohms from 2Hz to 400KHz
Phono stage input impedance 47 K Ω, adjustable with rear panel loading
Input overload 500 mV
Max output (at clipping) 120 V peak-to-peak
Gain 55 dB
Bandwidth 0.5 Hz-90 KHz within ½ dB
RIAA accuracy Within .1 dB
RIAA Phono sensitivity (for 0.5 V @ 1 KHz) 0.2 mV
Power Supply storage 50 Joules
Tube complement 7 x 12AT7, 2 x 6SN7GT, 2 x 12AU7
Dimensions 13″ deep x 17″ wide x 5.5″ tall (33 x 43 x 14 cm)
Faceplate dimensions (standard 3U rack) 19″ wide x 6″ tall (48 x 15 cm)
Weight 19 lbs. ( 8.6 kg )

£5520.00 (inc VAT) - Line Stage model
£6000.00 (inc VAT) - Phono Stage model