Усилители мощности стерео — Nuprime Audio AMG STA

The AMG STA belongs to the now discontinued AMG line of NuPrime Audio and was priced at USD 1,750 in a grey finish. It can be bridged into a mono amplifier, and its front panel is cut from a 15 mm block of hardened aerospace-grade alloy, machined with a diamond cutter over 48 steps on four CNC axes. Its 3D floating logo, curved surround at the power switch and diamond-cut edges are part of that design.

Key specs that matter

Stereo output is 2 x 130 W into 8 ohm and 2 x 200 W into 4 ohm. In mono mode it delivers 300 W into 8 ohm and 320 W into 4 ohm. Rated current is 10 A with 15 A peak. Gain is 26 in stereo and 52 in mono, and sensitivity is 1.2 Vrms in stereo and 0.95 Vrms in mono. Input impedance is 1 Mohm and output impedance is 20 milliohm. The signal-to-noise ratio is 100 dB at 10 W and THD+N is 0.006 percent. Frequency response runs from 10 Hz to 50 kHz within 0.2 dB into 8 ohm and reaches 58 kHz at -3 dB.

Engineering and use context

A Class A module in single-ended form with no negative feedback, using a 300 MHz bandwidth JFET, drives a double-feedback Class D stage. The Class D oscillating frequency is 700 kHz, 1.4 times that of the STA-9. The circuit board carries ground wire shielding against outside interference. The power supply uses a 380 W transformer with special winding that NuPrime rates at 30 percent more peak output than a transformer of similar volume. A high-current welding line links the AC inlet to the transformer, a third-order high-frequency filter cleans the incoming mains, and a 20 A lock-wire terminal block joins the transformer to the main board alongside two 10 A peak current rectifiers. The main current path uses a low-impedance copper plate. For mono operation NuPrime uses its Single-Ended Direct-Inject Bridge Technology instead of the usual op-amp inverter. The case measures 55 x 235 x 300 mm and weighs 4.5 kg, and NuPrime gives a two-year warranty. The packed unit measures 90 x 430 x 320 mm and weighs 6 kg, and the remote custom code is 0X06.

Pairing

RCA and XLR inputs are provided, chosen with a toggle switch, and only one of them should be connected at a time. The AMG DAC remote control can operate the AMG STA when the front power switch is set down. Its speaker outputs carry no DC offset and the negative terminal is ground, so they can feed a subwoofer directly.

Alternatives

The NuPrime STA-9 is a Class A+D stereo power amplifier rated at 2 x 120 W and bridgeable into a 290 W mono amplifier.