Интегральные усилители — Audio Research I/50

Audio Research built the I/50 tube integrated amplifier in Minnesota as a compact push-pull design. Its US launch price was USD 5,500 during the 50th anniversary of the company and was later replaced by the I/55, which kept its power rating and tube complement. Six Cerakote colour finishes were offered, and every unit ships with a full function remote control made of metal.

Key specs that matter

Rated output is 50 W per channel continuous from 20 Hz to 20 kHz. The output stage uses two matched pairs of 6550WE tubes, while three 6922 dual triodes serve as one input and two driver tubes. Frequency response at 1 W is 7 Hz to 30 kHz at -3 dB, and power bandwidth is 10 Hz to 22 kHz. THD at 1 kHz is typically 1% per channel at rated output and below 0.1% at 1 W. Input sensitivity is 1.25 V RMS, with input impedance of 100 kOhm balanced and 48 kOhm single ended. The case is 420 mm wide, 225 mm high and 360 mm deep, and it weighs 18.1 kg.

Engineering and use context

All of the audio circuitry, from input to output, is based on tubes. Around the back are one balanced XLR input, two RCA line inputs and a further RCA input configured as a pass-through. The loudspeakers connect to separate 4 ohm and 8 ohm taps on the output transformers, so the owner chooses the tap that suits the nominal load rather than relying on one winding. Headphones plug into a 6.35 mm jack. Two LexieTubes form the display, indicating which input is active and how high the level is set. The architecture is modular, with an optional moving magnet phono board offered at USD 800 and a D/A converter module announced for release in 2022. The output tubes need periodic bias checks, which on this model are carried out by hand. Mains supply is 105 to 130 V at 60 Hz or 210 to 250 V at 50 Hz, and the amplifier draws 252 W at rated output.

Pairing

MM cartridge owners can connect a record player directly once the phono board is fitted, and a home theatre processor can share the system through the pass-through input, which holds a fixed gain. Loudspeakers with reasonable efficiency make best use of its moderate tube power, and the choice of taps covers both common nominal loads. Any source with an XLR output sees a high input impedance, which it can drive easily. Digital sources need an external DAC unless the converter module is installed.

Alternatives

The Audio Research I/70 steps up in the same catalogue with KT120 tubes for 70 W per channel.