– Chad Olsen, summithifiusa.com

“As it turns out, I did not have to worry. With the Evolution STA in the system, there was no perceived loss of bass control. Indeed, there was the same control, but with a more detailed bass than the AMG STA’s. As cliche as it sounds, across the frequency spectrum, I was hearing things that I swear I had not heard before with the AMG STA’s. The Evolution STA was able to do all this while retaining the detailed yet smooth sound signature that I really like about Nuprime amplification. The Evolution STA represents the best class D implementation I have heard. This is a truly end game type amplifier for me.”

– Dick Olsher, theabsolutesound.com

“…First up was the Fleetwood Sound De Ville loudspeaker, a fairly benign 8-ohm bass-reflex load. Several sonic characteristics became evident rather quickly. First was the exceedingly low noise floor. Backgrounds appeared to be eerily quiet, more so than with the average solid-state amp and, obviously, without the tube-rush noise that I’ve become accustomed to. Second, resolution of low-level detail was superb. In particular, violin vibrato was exquisitely resolved with the sort of timing precision I’ve only experienced from far more expensive amps. But what surprised me the most was the Evolution STA’s ability to flesh out a believable depth perspective. In fact, the soundstage was exceptionally transparent, wide, and deep, with believable image focus. So now I’m thinking to myself, can a Class D amp really dish out this sort of imaging? And then it got even better. Micro dynamics were served up with emotional expressiveness. Orchestral crescendos were unfurled with tremendous power and control. And bass lines were punchy and tightly defined. It began to occur to me that this amp was going to be difficult to criticize.
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This scenario was much different than that presented by, say, a single-ended triode amp, whose distortion spectrum is rich in even harmonics and as a result dominates a system’s voicing. The NuPrime proved to be the total opposite. In this respect, it turned out to be a reference tool by
providing a truthful sonic snapshot of upstream components.
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Next in line was the Innersound Isis 3.5 hybrid electrostatic loudspeaker. This load has proven to be problematic for some Class D amplifiers due to its capacitive impedance and 2-ohm minimum through the upper octaves. Again, there was nothing of significance to criticize. ……..As you would expect from an electrostatic midrange and treble, transients were supremely well controlled, while the bass range was reproduced with control and full extension.
Finally, it was time for the Analysis Audio Omega. This quintessential planar speaker, an Apogee look-alike, has been a staple in my reference system for many years. It’s a 4-ohm nominal load, though it dips to around 3 ohms and demands a lot of current. In this context the NuPrime was able to generate a panoramic soundstage and believable depth perspective. Its level of micro dynamic finesse, purity of tone, resolution of individual voices in a complex mix, and rhythmic drive kept me listening late into the night.
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The NuPrime Evo STA caught me by surprise. I didn’t expect any amp at this price point, let alone a Class D amplifier, to be capable of such exquisite musicality. Mated with a compatible speaker load, it is deserving of an enthusiastic endorsement. It will not be leaving my system any time soon.”

– CHRISTIAAN PUNTER, hifi-advice.com

“…For my first listening, the Evolution STA was positioned on top of the CH A1.5, connected with the stock power cable, just like the A1.5, as the only exception in my system.
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The Evolution STA sounds marvellously energetic, expressive, and utterly coherent with immense neutrality but without tipping over into leanness or coolness. The amp is also very linear and quite detailed but not revealing to the point of being analytical, let alone clinical. First and foremost, it paints the complete musical picture while sounding nothing like your typical Class-D amplifier.
Between the CH and the NuPrime, certain key aspects have certainly noticeably shifted, but on the surface of it, and in an absolute sense, there is not very much to indicate that we just switched from a 31 K amplifier to one costing only 5 K. Honestly, it was more like switching from one high-end amplifier to another, invoking differences catering more to taste than to absolute quality. For instance, the Big Swiss amp remains the King of resolution and refinement. But to offset this, the NuPrime actually overshadows the CH in a couple of areas.
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The Evolution STA’s bass really is sublime and reminiscent of that of the Analog Domain M75, AVM Ovation A8.3, and Anthem STR. It is full-size, unrestrained, rock-solid, full-bodied, and weighty, but not in a thick, enriched, or loosely gripped manner as it can be with many powerhouse amplifiers, such as I feel is the case with certain Bryston amplifiers such as the 4B cubed. By the same token, the Evolution STA most definitely does not have the kind of bass that you’d expect from a Class-D amplifier, far from it actually. I have always found the bass from ICEpower, Pascal, and NCore amplifiers to be a little on the lean side, but as I found with the ST-10, NuPrime blissfully deviates from this pattern. It’s deeply saturated and full-bodied yet fast, articulate, and nimble.
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The amp sounds very much of one piece and its midrange follows the superbly well-balanced foundation in all parameters. Just like the bass, the midrange is concrete, clean, open, and expressive, without sounding lean or being devoid of saturation or harmonics. I’d go as far as to say that this is one of the best and most supremely neutral midrange performances that I have heard.
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A surprising strong suit of the Evolution STA is the soundstaging. In this area, the amp miraculously performs on par with the CD A1.5, providing a wide, deep, and room-filling stage with strong focus and depth.
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The Evolution STA is extremely neutral but never lean or clinical. What it does magnificently well is to lend weight, body, and saturation to instruments, and vocals alike, and with plenty of warmth if needed, but without ever tipping over into mushiness or ever sounding colored in any way. This amplifier sounds full-bodied and it can certainly sound smooth, warm, or romantic but only if the recording dictates it. It will not overlay the music with any added softness or warmth of its own.”