Интегральные усилители — Audio Research I/70

The I/70 is a tube integrated amplifier from Audio Research, introduced as the larger sibling to the I/50. It combines a separate active tube preamplifier section with a tube power amplifier, and its styling takes cues from the Reference 330M. The chassis comes in natural silver or black anodized aluminium, and Audio Research includes a new remote control machined from metal.

Key specs that matter

Rated output is 70 W per channel continuous from 20 Hz to 20 kHz. At 1 kHz total harmonic distortion is typically 1% per channel at rated power and below 0.1% at 1 W. Power bandwidth runs from 10 Hz to 22 kHz at the -3 dB points, and frequency response at 1 W spans 7 Hz to 30 kHz. Input sensitivity is 1.25 V RMS for full output, with input impedance of 100 kohm on the balanced input and 48 kohm on the single-ended ones. Standard analogue connections are one XLR balanced input plus three RCA single-ended inputs, and the total can reach eight inputs once the optional boards are installed. Speaker outputs offer 4 ohm and 8 ohm taps. Height is 210 mm, width 420 mm and depth 340 mm, and the unit weighs 25 kg.

Engineering and use context

The tube complement consists of two matched pairs of output tubes and three 6922 tubes, one at the input and two as drivers. Output-stage bias is handled by an auto-bias circuit and needs no manual setting by the owner. The output transformers are identical to those used in the Reference 75SE power amplifier. Polarity is non-inverting, with pin 2 positive on the balanced input to IEC-268. The volume control works in 75 steps. The headphone output is fed directly from the output tubes. The design is modular with room for two option cards. The DAC card is built around AKM Velvet Sound conversion, upsamples all incoming signals and accepts USB, coaxial, optical and Bluetooth sources. The phono card is specified for both MM and MC cartridge types, with MC loading adjustable from 50 to 1,000 ohm by remote. Mains requirement is 105 to 130 V at 60 Hz, or 210 to 250 V at 50 Hz in other versions, and consumption is 420 W at rated output and 220 W at idle.

Pairing

Audio Research designates the single-ended preamp outputs as preamp and subwoofer outputs, fed from the tube preamplifier stage. With both option cards installed, a turntable and digital sources connect without separate phono or converter boxes.

Alternatives

The Audio Research I/50 is the smaller sibling of the I/70 in the same integrated amplifier family.