Audio Research D-400 Stereo Power Amplifier – 200WPC, Solid State, With Original Box

Up for sale is a high-end Audio Research D-400 Stereo Power Amplifier, one of the finest examples of American solid-state amplifier design from the legendary Audio Research Corporation. Known for its power, transparency, and rock-solid build quality, the D-400 is ideal for audiophiles looking to drive demanding speakers with authority and finesse.

This delivers 200 watts per channel into 8 ohms and 400 watts per channel into 4 ohms, with a wide frequency response from 4 Hz to 100 kHz and a signal-to-noise ratio over 100 dB. It uses a fully differential balanced circuit, with both RCA and XLR inputs, and features a massive power supply with 270,000 µF of filter capacitance for deep bass control and dynamic headroom.

The amplifier is built like a tank, weighing approximately 76 lbs (~34.5 kg), and measures roughly 19" W x 8.5" H x 17.5" D. This unit is in excellent condition, functions perfectly, and includes the original factory box for safe shipping or long-term storage — a rare find for vintage high-end gear.

Cosmetically clean with minor wear consistent with age, no dents or damage. The front panel is pristine, and all rear connections are intact and solid. Unit has been carefully stored and lightly used in a smoke-free, climate-controlled environment.

Whether you're looking to upgrade your stereo system or build a powerful two-channel setup, the Audio Research D-400 delivers reference-grade performance that rivals much more expensive gear. It pairs beautifully with Audio Research preamps or any high-end analog or digital source.

Included in this sale:

• Audio Research D-400 Stereo Amplifier

• Original Factory Box

• Power Cable

This is the original D-400 (non-MKII) version. If you're comparing specs, be sure you're looking at the correct model — this listing reflects the standard D-400.

⚠️ Quick FAQ

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• Shipping/Pickup: "Local Pickup Only" means no shipping. Otherwise, carrier rates apply.
• Offers & Trades: Use the "Make an Offer" button if active. No trades. No DM negotiations.
• What’s Included: Exactly what is pictured/described. If it's not listed, it's not included.
• Returns: Sold as-is. Returns accepted for verified defective gear only; no buyer's remorse.
• Inspections: Prices are firm marketplace rates for quick pickup. Visual inspection welcome. Full audio bench testing/demos will increase the final price to cover time and setup labor.