NuPrime Audio AMG STA Power Amplifier

The AMG series front panel embodies its spirit. It is milled from a 15mm harden aerospace aluminum alloy using a four-axis CNC machine with a diamond cutter through a 48 steps process. Design elements such as the 3D “floating” logo, the curved surface around the front panel switch, and diamond-cut edge bring the quality of ultra-high-end audio products to the affordable range of the AMG series.

Technology

AMG STA PCB integrates ground wire shielding to isolate external interference. The 300 Mhz bandwidth JFET provides ultra-high input impedance and wide-band fast response. The dynamics of the design and the single-ended Class A circuit enriches the natural second harmonic.

This design allows the most delicate details in the audio signal to carry through the chain. The level of transparency in sound reproduction is genuinely astonishing in this class of equipment, with a deft in creating a highly detailed sonic imagery.

Power Circuit

A 20A lock wire terminal block connects the transformer to the motherboard, in parallel with two10A peak current rectifiers.

The main current path, adopting a large-capacity current design, uses a low-impedance copper plate to maximize power delivery to the amplifier circuits.

How did AMG STA mono achieve better sonic characteristic, in addition to more power than AMG STA stereo ?

The standard method for bridging a stereo amp into mono employs a series of op amps (OPA) in order to invert the input signals to one of the stereo amp, thereby creating an opposite phase, which can then be combined to increase power. Conversely, the AMG STA’s innovative bridging circuit utilises a design we call Single-Ended Direct-Inject Bridge Technology, in which the mono mode, in addition to acquiring more than double the power, sounds livelier and more dynamic.

Listening Impression

With improvements to every area, the bar has been raised for what is achievable with audio performance in small form factor.

The AMG STA has a flavor of its own, so it is hard to compare it with the Evolution One, which derives some of its design from or the similarly priced ST-10. AMG STA sounded smooth and relaxing. Detail, resolution, dynamics, and speed are in the ST-10 ballpark, yet the sound is quite different.

Drawing comparison with the Evolution One, they shared a trait of ease in reproducing the details of the recording comes afore. However, AMG STA does things differently. While the Evolution One has that inviting warmth, the AMG STA wants to allure the listener. Hence, instead of glitz and glamor, which pulls you in quickly into the performance, the AMG STA has a demeanor that slowly brings you into the music.

Tonal qualities of the AMG STA leans toward being full and rich, so instruments and vocals seem to gain extra body, weight, and harmonic richness. It may not be the most accurate reproduction but does make Jazz and Vocal pieces highly addictive. It may take away the raw edge of Rock and Electronic music and sounds less exciting for some.

The sound stage has an attractive characteristic. A linear presentation is like having floodlights shining on all the performers such that everyone can be seen equally well. The AMG STA, however, has more of a spotlighting effect, where performers are focused on getting your attention.

It is tough to put the sound of the AMG STA into measurable attributes as the presentation is quite different from the other series. You’ll need to try it and hear for yourself.