NuPrime AMG One Power Amplifier

My earlier shut encounter with a NuPrime power amp, the Evolution STA, was fairly memorable in that it made me understand that the efficiency hole between Class A and Class D amplification had shrunk significantly. In truth, I had little doubt that in particular system contexts, I’d have most popular the NuPrime to rather more costly typical amplifiers. NuPrime’s Jason Lim is sort of happy with the truth that his reasonably priced (sub-$5k) amps can compete with amps costing many instances extra. According to Jason, an excellent amp has to sound “proper” with a synergistic steadiness between element, dynamics, texture, energy, pace, and heat. During its analysis and improvement effort, NuPrime experimented with varied design concepts, together with GaN units working at a switching frequency above 1GHz. This resulted in pushing some sonic traits to the intense, however on the expense of others. Fine-tuning a Class D design is outwardly no straightforward job, however it appears to me that NuPrime is most undoubtedly heading in the right direction.

Currently, the Evolution STA and the Evolution Two (a pure mono model of the STA) sit atop NuPrime’s amplifier lineup. Think of the AMG One because the Evolution Two’s little brother, providing about half the ability supply in the same circuit topology, incorporating NuPrime’s proprietary “Only Distortion Cancellation” (ODC) suggestions circuit. As with the Evo Two, the design was tuned to run round a frequency of 650kHz, as this working level was decided to be optimum. The entrance finish is totally analog. Both the preamp stage and Class D pulse modulation circuit use the NJR MUSES8820 op-amp, which was particularly designed for audio functions. The enter impedance is 47k ohms, which needs to be passable for many preamps. The predominant circuit variations between the AMG One and Evolution STA are mentioned to be the ability transformer and the op-amp used within the ODC circuit.

My first set of listening impressions was obtained with a system primarily based across the Fleetwood Sound Company DeVille loudspeaker. As it so occurred, the AMG One changed a pair of superb sounding Tube Fantasy 300B SET monoblocks. I used to be most curious to find simply how nicely the NuPrime would talk the music’s internal pressure, one thing that the 300B SET excelled in. This is a prime precedence of mine, and a perceptual attribute that in my expertise solely a handful of solid-state designs have been in a position to totally convey. Of course, the notion of musical pressure is a mix of the rating’s structural parts similar to concord, melody, tempo, and dynamic markings along with the performer’s interpretation, which ultimately grants the music its expressiveness. When it got here to dynamic shadings and microdynamic inflections, I used to be stunned by how nicely the NuPrime held its personal. A CD such Jazz at The Pawnshop thirtieth Anniversary nonetheless sounded uninspiring in any case these years, whereas an almost 80-year-old recording of Dexter Gordon, Dexter Rides Again, completely got here to life.

The AMG One options distinctive specs with regards to harmonic distortion and signal-to-noise ratio. However, I’m at all times cautious and infrequently skeptical with regards to accepting amplifier specs as the ultimate arbiter of sound high quality. To echo none aside from Nelson Pass: “There has been a failure within the try to make use of specs to characterize the subtleties of sonic efficiency. Amplifiers with comparable measurements are usually not equal, and merchandise with greater energy, wider bandwidth, and decrease distortion don’t essentially sound higher.” This shouldn’t be shocking on condition that processing of the auditory stream is sort of advanced and includes billions of neurons to create a notion of the exterior stimulus. That mentioned, typically measurements do correlate with notion, as demonstrated by the AMG One. It floated a soundstage with a remarkably low noise flooring and sterling transparency. It was straightforward to retrieve low-level element aided by the virtually spooky silence between notes. The music ebbed and flowed with exemplary textural purity and with none apparent tonal bias.

For somebody like me, in the hunt for a heat steadiness, maximal tonal coloration saturation, and, to be completely candid, some tube-like textural liquidity, the NuPrime by itself was simply too trustworthy to fulfill my wants. One apparent approach of tilting the presentation in favor of tubes was to make use of a tube preamp. I attempted a number of earlier than selecting the Wyetech Labs Coral with upgraded output coupling caps. The Coral is fairly impartial, however it did add a contact of tube heat which is crucial to my enjoyment of reproduced music. During this course of it turned clear that the NuPrime precisely mirrored the sonic character of the related preamp and the flavour of the entrance finish. Good to know, since this makes it straightforward to mildew its sonic persona to swimsuit particular system wants.

After all of the tweaking was full, I turned totally conscious of a extremely clear, large, and deep soundstage, that includes well-defined picture outlines. On a well-recorded choral observe similar to “Shenandoah” by Cantus, I used to be startled by the 3D presentation of particular person voices. It turned clear that the AMG One may ship a spatial impression that almost all solid-state amps can solely dream of. Bass extension and impression had been excellent. Upright bass pitch definition was spot on, whereas tympani strikes took off with satisfying punch. Even in a pretty big room, energy reserve was sufficient for the DeVille. Transient pace and management had been additionally noteworthy, which accounted for vinyl floor noise being non-intrusive.

I ought to level out that the NuPrime sounds its finest about half-hour after being powered on, which brings up the plain chance of merely leaving it on to prepare dinner constantly. Unlike my Pass Labs Aleph 5, which dissipates 300 watts constantly in Class A and will get heat sufficient to fry an egg on prime of its chassis, the AMG One dissipates a mere 8 watts of idle energy per monoblock. Such an Earth-friendly amp is one main benefit of Class D.

It was time to modify listening rooms and mate the AMG One with the MoFi SourcePoint 10 loudspeaker. I used to be a bit involved in regards to the attainable consequence, because the Evo STA had not turned out to be a very good match, sounding too crisp and missing adequate midrange textural sweetness. The story was a lot totally different with the AMG One. Harmonic textures had been a lot sweeter sounding relative to the Evo STA, eliciting beautiful violin overtones, although nonetheless to not the identical diploma as a very good tube amp. For instance, in distinction with my Quicksilver V4 monoblocks, harmonic textures had been considerably much less liquid and wealthy sounding, probably the results of the Quicksilver’s distortion spectrum with its a lot greater ranges of second-order distortion merchandise. But as compensation, the AMG One provided much better bass definition and extension, in addition to enhanced soundstage transparency and immediacy. Overall, I discovered the AMG One to be a synergistic match for the SP10, highlighting its finest sonic attributes and making for a fully pleasant coupling.

Over the years I’ve been accused of being fairly fussy about solid-state energy amps, routinely discovering fault both because of an absence of textural purity or expressiveness. In explicit, solid-state sterility had pushed me to hunt musical solace in tube gear. That is certainly not the case with the AMG One. It is an pleasant amp, checking all of the packing containers on vital sonic metrics. The AMG One is presently not solely my favourite Class D amp but in addition considered one of my favourite solid-state amps. Retailing at $2900 per pair, I discover it to be aggressive at even a $10k value level. Plenty of energy and Class A-like finesse in an reasonably priced bundle make for a no brainer advice.

Specs & Pricing

Power output (RMS): 170W @ 8 ohms; 220W @ 4 ohms
Power output (peak): 210W @ 8 ohms; 260W @ 4 ohms
Sensitivity (for rated energy): 1.7V rms
Input impedance: 47k ohms
THD/S/N (typical): @5W (0.003%/95dB), @50W (0.004%/105dB), @100W (0.03%/110dB)
Frequency response: 10Hz–50kHz (-3dB)
Standby energy: 0.8W @ 115VAC
Idle energy: 8W @ 115VAC
Dimensions: 285mm x 55mm x 235mm
Weight: 5 kg
Price: $2900 per pair

NUPRIME INC.
Taipei City, Taiwan
nuprimeaudio.com

SUMMIT HI-FI (U.S. Distributor)
summithifiusa.com

Associated Equipment
Speakers: Fleetwood Sound Company DeVille & MoFi Electronics SP10
Preamplifier: Wyetech Labs Coral line preamp
(upgraded)
Phono entrance finish: Kuzma Reference turntable, Kuzma Stogi Reference 313 VTA tonearm, Clearaudio daVinci V2 MC Phono Cartridge; Sound Tradition MC-10 step-up transformer; Okay&Okay Maxxed-Out phono preamp
Digital entrance finish: Qobuz Streaming by way of Audirvana Studio; Denafrips Terminator & Schiit Audio Yggdrasil+ OG DACs
Cable & interconnects: Kimber Select & KCAG interconnects; TARA Labs RSC 500 Prime speaker cable
Accessories: Sound Application CF-X & TT-7 energy line conditioners; ALLDAC USB 3.0 & Topping HS02 USB Isolators; Herbie’s Audio Lab tube dampers