Audio Research D-80 Reference Series Fully Balanced 70 Wpc KT150 Tube Stereo Power Amplifier
By HiFi Editorial14 February 2026
Key Highlights
Audio Research D-80 is a fully balanced, two-channel tube power amplifier from the Reference series, delivering 70 W per channel in pentode operation.
The signal path remains fully balanced from XLR-only inputs to speaker terminals, minimizing noise and targeting modern high-end balanced preamplifiers.
Each channel uses matched KT150 output tubes with 6H30 drivers, covering 7 Hz–68 kHz at −3 dB and handling complex speaker loads confidently.
From an engineering standpoint, the D-80 reads like a deliberate exercise in restraint. Audio Research doubles down on a fully differential topology and pentode-only output stage, avoiding switchable modes or hybrid tricks that often complicate grounding and long-term stability. Pentode operation here is less about headline wattage and more about maintaining linearity under stress; with moderate global feedback applied, the circuit targets a balance between harmonic structure and control rather than chasing ultra-low distortion numbers at all costs. The specified distortion behavior—dropping to vanishingly low levels at small signal swings—suggests a design optimized for real listening levels, not bench theatrics.
