This is a mini-review with no formal rating because after about a week of listening to this product, its strengths and weaknesses were apparent. A longer listening interval, which would be normal for a full review, was not required to draw the following conclusions.
The reference system, on hand or in recent memory, included an Acoustic Signature Montana Neo turntable with Acoustic Signature TA-7000 Neo and Origin Live Agile tonearms; a ZYX UNIverse Optimum, Miyajima Destiny, and Tzar DST moving coil phono cartridges, DS Audio Grand Master optical cartridge; CH Precision P1-X1, Mobile Fidelity Master Phono and EMM Labs DS EQ-1 phono preamplifiers. Digital components on hand during the audition include a custom Windows computer running JRiver Media Center with USB-connected Bricasti M1 Series II DAC, and RME ADI-2 Pro fs r Black Edition AD/DAC with external power supply. The system also includes Luxman C900u and Benchmark HPA4 preamplifiers; Constellation Inspiration Stereo, Valvet E2 SE and Benchmark AHB2 power amplifiers; Alta Audio Celesta FRM-2M, B&W 805 D4, B&W 805 D4 Signature, and Magico S1 MkII speakers. The speakers are lightly augmented in the low bass, as needed, by a pair of JL Audio e110 subwoofers.
The audio cabling is Audioquest WEL Signature and Mogami interconnects and speaker cables. USB cables are Audience Front Row. Power cords include my DIY power cord and Straight Wire Pro Thunder. Headphones include Meze Elite and Hifiman Arya Stealth. Power protection and purification are provided by a PS Audio Dectet for the preamplifiers and source components, and a PS Audio Quintet for the power amplifiers. The Quintet includes a standard 1/8″ trigger connection enabling remote turn-on and -off of power amplifiers that lack a 12V remote trigger, which is a feature that every modern component should include.
I was interested in the Atma-Sphere “Class D” amplifiers because of in-home experiences with other Class D amps including products from NAD, EVS/VTV, Mivera, PS Audio, Emerald Physics/LSA, NuForce, Wyred 4 Sound, and Acoustic Imagery. I also reviewed other Atma-Sphere products over a decade ago. Atma-Sphere has a reputation for good sounding amplifiers, so a listen to their newest offering proved irresistible when a pair became available. The Class D mono amplifiers were used and fully broken in.
The sound of male vocals is the specialty of these amps. The lower midrange is delivered with very good warmth and humanity. Listen to “Combat Zone” on The Nylons 1986 LP Seamless. The singers sound very natural. This frequency range seems, unreliably, to have been where the development effort was focused, as male vocals are the highlight and strength of these amps.
The bass range is very full, like rolling thunder, while the detail and dynamic punch is quite limited. This issue with dynamics is pervasive across the entire musical spectrum and was clearly observed with or without comparison to either the Constellation or the Benchmark amplifier. Musical notes don’t seem to have the expected initial leading-edge impact. This problem is not akin to the overuse of compression during mastering as the leading-edge impactful sounds are mostly absent, not simply reduced in volume. We would often investigate a component’s rise time to gain insight into this anomaly. The result is that all music sounds musically dull and personally uninteresting.
So let’s add to this downer eval and talk about harmonics. Harmonics are those sounds which generally occur after the initial impulse and give the instrument or voice its character and identity. In this case, harmonics are limited. The natural fade out of a bell, triangle or other percussion happens far too quickly, robbing the sound of depth and character.
Due to the limited harmonics and associated low-level resolution, cymbals can sound like the hiss you might hear on an AM radio instead of sounding like ringing metal. Extension in the treble is good, but it’s a cloudy day with little air and ambiance due to the factors noted above. My listening notes have the comment “Like spacecraft, designed to work in a vacuum. Why is there a vacuum? No air!” You can blame Gentleman Jack for that one.
Gosh, this isn’t fun. I really wanted to like the sound from these amps. As you can probably understand by this point, a longer audition was purposefully avoided. One can hope that your results are more positive.
You buy an audio component because of reports that laud a product’s positive aspects. But you sell that same component due to its faults.