D400 MkII

About the D400 MkII

The Audio Research D400 MKII is a solid-state stereo power amplifier introduced in 1992, known for its high power output and wide frequency response. It delivers 200 watts per channel into 8 ohms and 400 watts per channel into 4 ohms, with a power bandwidth of 4Hz to 100kHz and low-level bandwidth extending from 0.01Hz to 160kHz. The amplifier features an input sensitivity of 2.0V RMS for rated output with 26dB gain, and input impedance of 57K ohms normal or invert, and 114K ohms balanced differential. It has an output regulation of 0.06dB from 8 ohm load to open circuit, overall negative feedback of 9.7dB, and a damping factor of 150. The slew rate is 50V/µs with a rise time of 1.0 µs. Hum and noise are less than 220 µV RMS, 105dB below rated output (IHF A-weighted). The power supply energy storage is 270,000 µF, and power requirements are 105-125VAC 60Hz (210-250VAC 50Hz), consuming 760 watts at rated output and up to 1200 watts maximum. The amplifier supports both single-ended and balanced inputs, including a second set of inverting single-ended inputs for balanced operation in two modes, and bridged mono operation for higher power output. It is designed with a peak output current of 60 amps into 1 ohm and non-inverting input polarity. The D400 MKII is highly regarded for its excellent low-end extension and clean, powerful sound.