Усилители мощности моно — Audio Research VT80 SE

Audio Research builds the VT80 SE as a two-channel valve amplifier, hand-assembled in Minnesota and styled in the look of the brand's Foundation Series. Audio Research presents it as the amplifier in its range meant for the widest group of listeners, pairing a fully balanced circuit with conveniences such as automatic biasing. Four output tubes, fitted as matched pairs, and two 6H30 drivers stand on an open chassis.

Key specs that matter

Output is 75 W per channel continuous from 20 Hz to 20 kHz, and total harmonic distortion at 1 kHz is typically 1% at full power and below 0.05% at 1 W. Power bandwidth spans 7 Hz to 60 kHz at the 3 dB points, and response at 1 W runs from 0.7 Hz to 80 kHz. Input sensitivity is 1.4 V RMS balanced for rated output, giving 25 dB of balanced gain into 8 ohms. Input impedance is 300k ohms balanced and 150k ohms single-ended. Channel separation and the signal to noise ratio are both 112 dB, and hum and noise measure 84 dBV below reference, weighted, at the 8 ohm tap. Overall negative feedback is 15 dB, the slew rate is 10 volts per microsecond, and the rise time measures 4.0 microseconds.

Engineering and use context

A proprietary auto-bias circuit sets the bias for each output tube and keeps correcting it in real time for tube wear and mains fluctuations, and it reacts at once when a new tube is fitted. Each output tube has its own protective fuse, which can be replaced if a tube fails. The power supply stores approximately 350 joules. Controls cover power, auto shut-off with a defeat option, balanced or single-ended input selection, an RS232 port and a 12 V trigger. Steel construction forms the chassis. Consumption is 230 W at idle, 410 W at rated output and 500 W maximum, with sleep power under 1 W, and versions exist for 100 to 125 V at 60 Hz and 200 to 250 V at 50 Hz. The amplifier is 48.3 cm wide, 26.2 cm high and 46.8 cm deep to the chassis, or 49.3 cm to the terminals, and weighs 20.7 kg net or 27.4 kg packed for shipping. Ambient air temperature must not exceed 30 degrees C.

Pairing

Speaker outputs are provided for 8 and 4 ohm loads, and output regulation of about 1.0 dB from an 8 ohm load to open circuit equals a damping factor near 8. Finishes are Black and Silver.

Alternatives

The Audio Research Reference 80S is a fully balanced stereo amplifier with four KT150 output tubes, switchable Triode and Pentode modes and 16, 8 and 4 ohm taps.