Усилители мощности стерео — PS Audio S300 Amplifier

The Stellar S300 is a two-channel power amp made by the Colorado firm PS Audio for its Stellar range. It combines a discrete Class A input circuit with a Class D output module, and PS Audio describes it as a dual mono design, with a separate power supply and amplifier stage for each channel. PS Audio sells it for USD 1,999 in the US, in black or silver, and covers it for three years on parts and labour against defects.

Key specs that matter

Output is 140 W per channel into 8 ohm and 300 W per channel into 4 ohm, and the amplifier is rated as stable into 2 ohm. THD stays below 0.1% from 20 Hz to 20 kHz at rated power. Gain is 30.5 dB, and 1.01 V at the input is needed for full output. Input impedance is 50 kOhm unbalanced and 100 kOhm balanced. Output impedance is below 0.007 ohm at 50 Hz, which gives a damping factor above 1,100 into 8 ohm and above 550 into 4 ohm. Measured into 4 ohm at 2.8 V, response holds within 0.5 dB from 10 Hz to 20 kHz and reaches 50 kHz at -3 dB. Noise at full 300 W output is below -100 dB. The case is 432 mm wide, 76 mm tall and 305 mm deep, or 330 mm deep including connectors, and weighs 5.9 kg.

Engineering and use context

PS Audio calls the input section the Analog Cell - a proprietary, fully differential circuit built from discrete MOSFETs that runs in Class A without feedback. The output stage is an ICE Class D module designed in Denmark, chosen for its linearity and high current capability. Because the switching output stage runs cool, idle consumption is only 13 W, and the slim chassis needs no large heatsinks, so the amplifier fits on a standard shelf and can sit under a preamplifier. A standby button is placed on the front panel, and the unit takes mains through an IEC C14 socket.

Pairing

Inputs are provided on both RCA and XLR, so the S300 accepts single-ended or balanced preamplifiers, including the matching Stellar line components. Each channel has two pairs of nickel-plated copper binding posts, which allows bi-wiring without jumpers at the amplifier end. A 3.5 mm DC trigger input accepting 5 to 15 V lets a preamplifier or processor switch it on remotely. The high damping figure and stability into very low loads allow it to drive loudspeakers with low impedance or modest sensitivity.

Alternatives

The PS Audio BHK Signature 250 steps up to a heavier two-channel design in the PS Audio catalogue, using a vacuum tube input stage with MOSFET outputs and rated at 250 W per channel into 8 ohm.