Atma-Sphere Atma-Sphere Gem Amplifier
Atma-Sphere’s compact tube integrated delivers crystal-clear transparency, startlingly fast transients and a vividly dimensional soundstage. K. E. Heartsong at AUDIOKEY REVIEWS found its deep, controlled bass, airy treble and lifelike musical presence exceptional—even when driving demanding Susvara headphones through an adapter. It is a focused, minimalist amplifier for listeners who prize insight, speed and tonal texture.
WATT RECOMMENDS
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Deliciously Crispy
Sound Quality
95/100
Build Quality
84/100
Value for Money
88/100
Pros
Exceptional transparency, detail retrieval and realism, surpassing the reviewer’s established headphone-amplifier reference.
Deep, tight and highly resolved bass combines with extended, clean treble and a refined, textured midrange.
Lightning-fast transients, decisive dynamics and a large, layered soundstage create an unusually lively presentation.
Compact, straightforward design with simple controls; its five watts successfully handled very demanding headphones when used with an adapter.
Cons
Feature set is deliberately sparse, with only two single-ended inputs and basic front-panel controls.
The tightly positioned IEC/fuse area may not accommodate most aftermarket power cords.
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What Reviewers Are Saying
SOUND QUALITY PERFORMANCE 95/100
The available review finds the GEM unusually clear, vivid, fast and spatially convincing, repeatedly comparing it favorably with established reference headphone amplifiers. Its presentation combines finely resolved detail and tonal texture with notably forceful bass, transient precision and immersive dimensionality.
Transparency Resolution
96/100
The reviewer calls the GEM “eminently more transparent and resolving” than the Aurorasound HEADA reference, with a more profound sense of realism. Crystal clarity, copious low-level detail and the ability to reveal information other amplifiers miss are recurring observations.
Tonal Balance Musicality
94/100
The GEM is described as extended and linear from deep, resounding bass to pristine treble, while the midrange is praised for refinement, texture and palpability. The reviewer also hears an emotive, SET-like quality without suggesting softness or tonal imbalance.
Dynamics
95/100
The review praises lightning-fast transients, incisive leading edges and “stop-and-start-on-a-dime” dynamic behavior. Its five watts were reported as fully capable in the reviewed headphone use, delivering an unusually lively and immediate presentation.
Soundstage Imaging
96/100
The GEM is credited with a large, growing soundstage that matched or exceeded the reviewer’s ALLNIC HPA 10000. Musicians are portrayed with convincing placement, depth, air and volume, making small performance details feel intimate and immersive.
Assessments of Build Quality, Usability, and Overall Propositions.
Build Quality
84/100
The reviewer describes the compact GEM as a straightforward, utilitarian design rather than dwelling on lavish construction. Its tube complement, separate 4- and 8-ohm outputs, two inputs and simple front-panel controls suggest a focused, practical implementation, but the review says little about long-term durability or internal construction.
Value for Money
88/100
At $4,700, the GEM costs substantially more than the $2,999 Aurorasound HEADA used as a reference. Even so, the reviewer says no previously reviewed headphone amplifier was as talented or capable, including that long-standing reference, supporting the case for a justified premium rather than a budget proposition.
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Specifications
- frequency response
- 5 Hz-100 KHz, +0 dB, -2dB@ 1/2 Watt
- input impedance
- 100 Kohm Ω
- Outputs
- 4 and 8 Ohms
- Tube complement
- 4 x EL95 (6DL5 or 6BM5); 2 x 12AT7
- Dimensions
- 12" deep (including knob and connectors) x 7" wide x 5" tall
- Weight
- 12 lbs. 15 oz.
- Warranty
- Three years, transferable\nOne year for tubes
Manufacturer's Description — Atma-Sphere
Hi-End 5 Watt tube amplifier
The Gem is a Push Pull class A tube amplifier meant for bedroom, desktop, headphone or main system use. It uses many of the concepts we use in our other amplfiers. Its fully differential from input to output (RCA inputs only). It is overbuilt with precision parts; for example the output transformers are rated for 10 Watts so the amp can't get in trouble should a power tube fail. It can drive 4, 8 or 16 Ohm loads. This amp uses the same parts quality of our highly regarded OTLs and has power supply capacity found in many amps of 5x more power.
This was originally designed as an amp for a bedroom system where reliability is paramount. Its low noise suits headphone use as well; its attractive and small enough that it is suitable for use in a good quality desktop or home main system (if the latter has higher efficiency speakers).
We considered building a Single-Ended Triode (SET) amp for this project and so a number of designs were tried. SETs have a strong following; their proponents claim they sound better than push-pull amps. But output power and class of operation are never the same in any comparisons so far... So we found that if just these two variables are eliminated, SETs have no advantage over a properly designed and built push-pull amp, by any metric important to audiophiles. We were able to get the same power in a smaller space with wider bandwidth (most easily heard in the bass region where SETs are at their worst) and lower distortion, which translates to 'more transparent' since distortion obscures low level detail, and smoother for the same reason.
Features
- Fully Differential Design
- Two inputs with volume control- Suitable for headphones, desktop, bedroom or a main system with efficient loudspeakers- Two stage Constant Current Sources for each stage of gain (improves performance of each gain stage)
- Precision components used throughout
- Low-noise "star" grounding topology- Three-year general coverage warranty with one year warranty on output tubes
Verified Dealers
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Authorized dealers for Atma-Sphere Atma-Sphere Gem Amplifier
- Afton Mountain Audio — in-store — Afton, Virginia, United States (website)
- Audio Perfection — online and in-store — Minneapolis, Minnesota, United States (website)
- Audio Revolutions — in-store — Khwaeng Thung Phaya Thai, Krung Thep Maha Nakhon (website)
- Phantom Audio — in-store — Jakarta, Jakarta, Indonesia (website)
- Salon One Audio — in-store — Ormond Beach, Florida, United States (website)
- Signature Sound — in-store — Liverpool, New York, United States (website)
- Sounds Of Silence — in-store — Nashua, New Hampshire, United States (website)
- Sun Mountain AV — in-store — Colorado Springs, Colorado, United States (website)
- Triode Picture + Sound — in-store — New York, New York, United States (website)
- USA Tube Audio — online and in-store — Phoenix, Arizona, United States (website)
and 1 more verified dealer