Усилители мощности стерео — PS Audio BHK Signature 250 Amplifier

The BHK Signature 250 is a two-channel hybrid power amplifier from PS Audio of Boulder, Colorado, designed by the late Bascom H. King, whose initials give the series its name. Its circuit places triode tubes ahead of a MOSFET output section. The regular US price was USD 8,499, and PS Audio lists the model as discontinued from new production in 2024. A monoblock sibling, the BHK Signature 300, was offered in parallel with this stereo unit.

Key specs that matter

Rated output is 250 W per channel into 8 ohm and 500 W per channel into 4 ohm as a short-term figure, with 200 W given as the long-term 4 ohm rating under IEC60065, and the amplifier is stated to be stable into 2 ohm. Gain is 30.5 dB and 1.3 V at the input drives it to full output. Input impedance is 100 kOhm on RCA and 200 kOhm on XLR, while output impedance stays below 0.1 ohm at 50 Hz. Response is flat within 0.1 dB from 10 Hz to 20 kHz and reaches 125 kHz at the -3 dB point. THD is under 0.01% at 1 kHz and 1 W, and under 0.1% at 200 W into 8 ohm. Signal to noise is quoted at better than -85 dBV. The chassis measures 434 x 221 x 356 mm, or 381 mm deep with connectors, and weighs 37.6 kg.

Engineering and use context

The input stage runs a hand-matched pair of Gold Lion 6922 triodes with automatic bias, so other 6- or 7-series triodes can be fitted, and PS Audio suggests replacing them every one to two years at a few hours of daily use. The output stage uses only N-channel MOSFETs instead of a complementary layout, a choice the company links to better balance and lower distortion. Two separate power transformers feed the tube section and the output section, and the analog supplies use discrete MOSFET regulators. All boards are built with through-hole parts, with no surface-mount devices. Pressing the front logo puts the unit in standby, which switches the tubes off while the solid-state circuits stay in a reduced-power mode. Mains draw is 75 W in ready mode, 175 W at idle and up to 1,600 W at full rated output.

Pairing

With RCA and XLR sockets on the back, the amplifier can follow any line-level preamplifier, and each channel carries two pairs of gold-plated copper binding posts for bi-wiring. A 3.5 mm trigger input accepting 5 to 15 V DC lets a preamplifier switch it on and off. The high current rating and stability into very low loads suit low-impedance or low-efficiency loudspeakers.

Alternatives

The PS Audio Stellar S300 offers a lighter two-channel option in the PS Audio catalogue, built around a Class D output module and rated at 140 W per channel into 8 ohm.