Nuprime Audio STA-9
Image source — © Nuprime Audio
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Model name
STA-9
Input sensitivity (mV)
232.8
Input impedance (balanced) (Ω)
47 000
Input impedance (single-ended) (Ω)
47 000
Output impedance (balanced) (Ω)
N/A
Output impedance (single-ended) (Ω)
20 000 000
Max current (A)
N/A
Output power (8Ω) (W)
280
Output power (4Ω) (W)
320
Gain (dBu)
x22
Frequency response low +/- 3dB (Hz)
10
Frequency response high +/- 3dB (Hz)
50 000
Signal to Noise Ratio (dB)
<95
Total Harmonic Distortion + Noise (0% global feedback) (%)
N/A
Total Harmonic Distortion + Noise (100% global feedback) (%)
0.01
Max power consumption (W)
N/A
Damping factor
N/A
Dimensions (mm)
55 x 235 x 281
Weight (kg)
4
Official link
The “Power Engine” is a low-power switching power supply (SMPS) for low voltages on the amp board. The large linear power supply provides high voltages for the Class-D power stage. According to the manufacturer, they have made a breakthrough in SMPS design that can rival linear power supplies. This “Power Engine” is the first use of such a design for AMG STA-SE.
The NuPrime AMG STA includes several advanced power amplifier design innovations. Its best-in-class features include a 1 mOhm input impedance, high instantaneous current for power supply, a 700 kHz switching frequency, and an unbalanced Class A non-negative module combined with a Class D dual feedback module for 300W mono amplifier power.
NuPrime is a small AMG STA power amplifier capable of delivering 300 watts at 8 ohms in bridge mode and 320 Watts at 4 ohms load. He achieves such indicators by using a clever scheme that combines two cascades – one in class A on JFET transistors and the second in class D. In traditional stereo mode, the power is 120 watts per channel at 8 ohms and 200 watts at 4 ohms.
The STA-9 is a Class A+D stereo amplifier. In stereo mode, its power is 120 watts per channel, but it can also work in mono amplifier mode with a power of 290 watts. The amplifier circuit is borrowed from the IDA-8, which is based on a high-impedance class A pre-stage and a Class D power stage. Thanks to this, the novelty sounds "almost lamp-like", but at the same time it is clear and reliable. The 95 dB signal-to-noise ratio is achieved by JFET transistors simulating triodes.