AUDIO RESEARCH HD220

Second-hand. In excellent conditions. Free of visible signs of wear. Comes with original packaging and manual.

The Audio Research HD220 is a hybrid power amplifier designed to combine the best of tube and solid-state technology, with the goal of delivering musicality, realistic dynamics, and an outstanding soundstage.

Introduced at CES 2007, the HD220 delivers 220 watts per channel into 8 ohms and nearly 400 watts into 4 ohms, offering remarkable dynamic drive and the ability to power even demanding speakers with authority. The design is based on Hybrid Drive technology, featuring a low-noise JFET input stage feeding a 6922 dual-triode for gain, followed by a 6H30 dual-triode cathode follower. This signal path preserves musical integrity and natural reproduction while ensuring high transparency and a smooth, grain-free sound.

The output stage employs twelve Thermal Trak® bipolar devices per channel, which automatically adjust bias according to operating temperature. This ensures consistent performance and stability even under demanding loads. Cooling is managed by a low-noise fan, while the fully solid-state power supply provides an energy reserve of 200,000 µF, delivering deep and controlled bass impact.

The HD220 is built for long-term reliability: the input stage tubes operate conservatively for extended lifespan, and a convenient indicator allows users to monitor tube hours. Since there are no output tubes to replace, maintenance is minimal. Both balanced and single-ended inputs are available, while the gold-plated copper output connectors ensure optimal signal transfer.

Sonically, the HD220 offers exceptional transparency and tonal purity, with extremely low distortion and minimal noise levels. The dynamics are explosive, and bass control is firm and articulate, whether driving dynamic or planar speakers. The combination of the finesse of the tube stage and the power of the solid-state stage results in a detailed and engaging listening experience, capturing both delicate micro-details and the full weight of orchestral crescendos.

The Audio Research HD220 is an ideal choice for those seeking high-performance sound reproduction without the need for periodic output tube replacement. This amplifier marks a new chapter in Audio Research’s history of high-definition sound.

Technical Specifications:

• Power Output: 220 watts per channel into 8 ohms from 20Hz to 20kHz; 380 watts per channel into 4 ohms.
• Power Bandwidth: Frequency response (-3dB at 1 watt) from 0.5Hz to 200kHz.
• Input Sensitivity: 4.0V RMS balanced for rated output (20.8 dB balanced gain into 8 ohms).
• Input Impedance: 300K ohms balanced, 150K ohms single-ended.
• Output Impedance: Regulation of approximately 0.07dB from 8-ohm load to open circuit.
• Damping Factor: Approximately 130.
• Hum & Noise: Less than 0.1mV RMS, -112dB below rated output (IHF weighted, input shorted).
• Power Supply Energy Storage: 200,000 µF.
• Power Requirements: 105-125VAC 60Hz (210-250VAC 50Hz), 750 watts at rated output (220 WPC into 8 ohms), 1200 watts max (380 WPC into 4 ohms), 250 watts at idle.
• Tube Complement: (2) 6H30 driver tubes, (2) 6922 voltage amplifier tubes.
• Balanced Input: Pin 2+ (IEC-268).
• Dimensions: 19" (W) x 8.75" (H) x 19.5" (D).
• Handles: Extend 1.5" forward.
• Weight: 58.9 lbs. (Net).