Усилители мощности моно — Audio Research Reference 330M

The Reference 330M is a vacuum tube monoblock power amplifier built by Audio Research in Minnesota, which the company unveiled at the 2024 Munich High End. The signal path uses tubes throughout, and the circuit is a fully balanced class AB design that still accepts single-ended sources.

Key specs that matter

Audio Research rates the output at 330 W at 1 kHz with 0.92% THD+N measured over a 10 Hz to 80 kHz bandwidth, and at 1 W the distortion figure drops to 0.013%. Frequency response extends from 0.5 Hz to 110 kHz at minus 3 dB and 1 W. For rated output the balanced input needs 2.48 V RMS and the single-ended input 1.23 V RMS. Input impedance is 168.5 kilohm balanced and 19.5 kilohm single-ended, output impedance is 0.812 ohm, and the damping factor is 10 into 8 ohm. Noise, referenced to 1 W into 8 ohm, is minus 80 dBV unweighted and minus 91 dBV A-weighted on the balanced input, against minus 75 dBV and minus 86.5 dBV single-ended. Power consumption is 987 W at rated output, 386 W at idle and 1.1 W when switched off. Its enclosure is 47 cm wide, or 48.26 cm with the faceplate, 26 cm high and 54.6 cm deep, growing to 61.6 cm with handles and connectors, and it weighs 46 kg, or 54 kg packed for shipping.

Engineering and use context

Six KT170 output tubes provide the power, driven by a 6H30 and a 12AX7 or ECC83 gain stage, while a 6550 and another 6H30 serve as regulators in the power supply. Automatic bias keeps the output tubes at their operating point, and Audio Research quotes an output tube life of 3,000 hours, tracked by a built-in tube hour meter together with tube monitoring. Cooling fan speed is controlled by the amplifier. The front meter has switchable lighting and a needle that can be turned off. For system integration there is a 12 V trigger input, RS232 control and an automatic switch-off after two hours without signal that can be disabled. Mains power enters through a 20 A IEC connector. The warranty covers the amplifier for three years and the tubes for 90 days.

Pairing

Binding posts for 4 ohm and 8 ohm are provided, so the output transformer tap can follow the nominal impedance of the loudspeaker. Because the design is balanced, a preamplifier with XLR outputs uses the circuit as intended, though RCA connection remains possible. A stereo system uses two chassis, one per channel.

Alternatives

Audio Research also offers the Reference 160M MkII monoblock, which uses four KT150 output tubes to deliver 140 W continuous from 20 Hz to 20 kHz.