AMG STA Amplifier Review by Spec Of Tech
Why I Switched to Class D Amps! Small But Mighty

– Christiaan Punter, hifi-advice.com

“…
The AMG-PRA + AMG-STA form a beautiful combo, not only visually, but also in terms of sonic synergy, the preamp’s robust and full sound perfectly complimenting the power amp’s slightly leaner balance. The combined result is a musically always engaging sound that is solid and full-bodied, smooth and refined yet highly detailed and transparent, with perfect pacing, and great dynamics. Honestly, at 3200 euro, I haven’t heard a better amplifier, either integrated or separates.

As great as the combo is, the AMG-STA power amplifier really is the star of the show. On its own, it is capable of performing on a level that is well and truly beyond what might be expected from an amplifier at its price point. To be more precise: if the preamp already performs at a level that belies its price sticker, the power amp steals the show as it has the ability to perform on the level of amplifiers that typically cost multiples of its modest 1.595-Euro price. I am not kidding!

Combine the AMG-STA with a great volume-controlled DAC and you’ll have a nearly unbeatable system. Between single and dual amps, if ever there was a no-brainer decision, this is it. The pair simply raises the performance in each and every audiophile parameter, without harming the emotional involvement.

As should be clear by now, I am definitely impressed by NuPrime power amplifiers. First, the ST-10 proved to be a keeper, then the ST-10 Monos proved that the concept could be taken further, then the AMG-STA proved that Class-D can be as “analog” and as refined as the best linear power amplifiers, and now, the pair of AMG-STA’s have further raised the bar. Although the ST10 and ST10 Monos still have their unique flair, as of now, the pair of AMG-STA’s are my personal reference in the field of affordable power amplifiers with true high-end aspirations.

Whether used as a single stereo model or as a double-mono pair, the AMG-STA is an absolute HFA Favorite.”

– CHRISTIAAN PUNTER, hifi-advice.com

“The AMG STA not only addresses all of the ST-10’s weaker areas but actually raises the overall quality to such an extent that it comfortably positions itself among high-end competitors that cost multiples upon multiples. Alas, in the process, it does give up a portion of the ST-10’s bass heft and overall robustness. But otherwise, it sets the benchmark, not only in its price class but also far, far beyond.”

– Mikkel Gige, HiFi4All

AMG PRA
“But then the sound also immediately became much more forgiving, and the soundscape clearly grew in all three dimensions. Likewise, the bass became more nuanced and detailed while the weight was still present. And that meant I could now start listening to other things in the music. At the same time, listening to STA became a very musical pleasure. And it was here that it became clear that the sound is very similar to PRA. However, STA does not have quite the same slap and dynamics as PRA, but it is also completely unique in that area.
It also meant that I actually stopped thinking more about the sound, and instead just enjoyed the music. As if by magic, there was a presence in the music, and both voices and instruments gained naturalness a la what I know. And the sound just stretched further up towards the high frequencies completely without artifacts or anything else that could interfere with the experience.
…
… I give Nuprime AMG PRA the award “Best Buy” along the way!

AMG STA
“…And the bass sounded like what was known in the “old days” as typically “at D-bass”: Lots of level and weight, but no details and nuances!
…
But then the sound also immediately became much more forgiving, and the sound image grew clearly in all three dimensions. Likewise, the bass became more nuanced and detailed, while the heaviness was still present. And that meant I could now start listening for other things in music. At the same time, it was a great musical pleasure to listen to STA. And it was here that it was clear that the sound is very similar to PRA. However, STA does not have quite the same punch and dynamics as PRA, but it is also quite unique in that area.
…”

– Drew Kalbach, The Absolute Sound

AMG PRA
Overall, the PRA’s design is simple, but attractive and effective.
…
Before I dive into listening, it’s time to look at the “Active Low Frequency and Harmonic Gain” control feature. To put it very simply, this knob is somewhat like Ye Olde Loudness switch of yore. When turned on it very noticeably boosts bass, without increasing the overall volume. It is an interesting EQ effect, and definitely achieves NuPrime’s stated goal of giving smaller speakers a bit more natural low end. It worked well with my Wharfedale 225s, and actually sounded fairly nice with my Omen Dirty Weekend on its lowest setting. However, through the Polk L600 (review forthcoming), the knob made the bass a little too flabby, which makes sense. (The L600 have a very deep low end, and compensating made the bass a little too intense.)
…
The backgrounds were shockingly black, and it almost felt as if the AMG PRA preamp was nearly transparent, if you’ll forgive a reviewing cliché. That deep noise floor allowed the music to shine with a crispness and dynamism that I absolutely loved.
…

AMG STA
…“Active Low Frequency and Harmonic Gain” control feature. To put it very simply, this knob is somewhat like Ye Olde Loudness switch of yore. When turned on it very noticeably boosts bass, without increasing the overall volume…It worked well with my Wharfedale 225s, and actually sounded fairly nice with my Omen Dirty Weekend on its lowest setting.
…
The single STA was more than enough to power my Zu Omen Dirty Weekends, and made my copy of the recent Ray Charles vinyl reissue Genius + Soul = Jazz sing and scream and shout. Lows were suitably solid, and the midrange really shone with an extremely pleasant smoothness. I never felt as though the AMG STA lagged behind or ran out of headroom powering the Zu DWs, even on this very dynamic recording.
…
Where this dual-mono configuration really worked was with the Polk L600s, the more difficult pair of speakers to drive. The AMG STA retained its signature relaxed and easy sound, but with that much power on tap really opened up the full potential of the Polks. The backgrounds were shockingly black, and it almost felt as if the AMG PRA preamp was nearly transparent, if you’ll forgive a reviewing cliché. That deep noise floor allowed the music to shine with a crispness and dynamism that I absolutely loved.
…
Williams’ fills sounded exuberant and rhythmically complex, and the system never compromised or slowed down his fascinating drumming. In the midrange, the piano and horns were smooth and silky with a hint of nice, heavy warmth down in their lower regions. Hancock’s solo was quick and slithering, like the song’s namesake, and each note was clearly delineated. Attacks and decays were on point, which added to the whole rhythmic picture building throughout the song. When the horns massed for the theme, each instrument remained wholly itself and focused, creating a wide sense of soundstage. The STA/PRA dual-mono combo worked very well with the L600s, since the speakers have a very solid and deep lower end, and the amp/preamp shines in the lower registers. It was that deep heft that really brought a difficult song like “King Cobra” to life, and leant the entire ensemble a massive sound.
…
For many folks, I suspect a single STA will provide enough power, but for those who have more difficult-to-drive speakers, or those who want a massive amount of power on tap and ready to go, the monoblock setup is fantastic. This is a system worth trying and comes highly recommended.