[rustydoglim]

Evolution STA review is on the September issue of The Absolute Sound. I think this is as good as it gets for a review.
Highlights from the review:

“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.
……
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.
……
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.
……
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.

[mresseguie]

Congratulations on such a positive review, Jason. 

My own Evolution STA has been in my system for about six months now, and I happily concur with this reviewer’s description. Your engineers have done a wonderful job!

Michael

[morganc]

Michael I’m curious, are you pairing your STA with a Don Sachs ?  What speakers are you using ? 

[mresseguie]

Michael I’m curious, are you pairing your STA with a Don Sachs ?  What speakers are you using ?

Good morning 🌞!

Yes, I have been pairing it with my Don Sachs preamp and my Daedalus Audio Apollo speakers. What I discovered was that the gain setting between the preamp and amp was a tad too high, which resulted in a ‘just barely noticeable’ hiss from the speakers.

I discussed this situation with Don, who said he could slightly decrease the gain setting from the second out while leaving the gain from the first out unchanged (because this best suits pairing to my Kootenay 120 amp). As long as I was going to have Don do this, I decided to have the caps changed to Vcaps, replace the volume control and a couple other things which have slipped my mind.

I got the preamp back last week, and I couldn’t be happier. [Okay. I’ll be happier once the new caps have fully burned in.] It now perfectly matches both amps.

Michael