The Audio Research I/55 integrated amplifier advances the compact, all-tube platform of its predecessor with the control and connectivity refinements introduced in the I/70. Its amplification circuit pairs two matched sets of 6550WE power tubes with 6922 input tubes, delivering 50 watts per channel of continuous power with the harmonic richness and dynamic agility that have long defined the brand. The addition of auto-bias circuitry keeps the output tubes operating in their optimal range throughout their service life, simplifying ownership while preserving the amplifier’s expressive bass response and transient speed.
An active tube preamplifier stage offers a wider gain range and greater headroom than the passive design found in earlier models, making it particularly effective with recordings cut at low levels for extended dynamic range. Connectivity includes three single-ended inputs, one balanced XLR input, and a built-in DAC built around an AKM Velvet Sound chip that handles high-resolution PCM via USB, optical, coaxial, and Bluetooth—each upsampled for improved transparency and tonal purity. A dedicated headphone output driven by the 6550 output tubes, stereo preamplifier outputs for subwoofer integration, and an optional phono card with adjustable MC loading and MM/MC gain settings round out a versatile feature set housed in a chassis measuring 16.5 inches wide.