audio research
D-90

Description
Tube stereo power amplifier.

Introduced
1980

Discontinued
1985

Revisions
D-90 Revised
D-90B (1981)

Options
-

MSRP (US new retail)
D-90: $2,195
D-90B: $2,450. Later increased to $2,695.

Specifications

Power output 90 watts per cannel minimum continuous (both channels operating) at 16 ohms from 25 Hz to 20 kHz with less than 1% total harmonic distortion. Typically below .01% at 1 watt. Approximate power available per channel at "clipping" (both CH. OP, 1kHz): 105 watts
D-90B:
80 watts per cannel minimum continuous (both channels operating) at 16 ohms from 25 Hz to 20 kHz with less than 0.5% total harmonic distortion. Typically below .005% at 1 watt. Approximate actual power available per channel at "clipping" (both CH. OP, 1kHz): 90 watts
Power bandwidth (-3dB points) 12 Hz and 60kHz
D-90B: (-3dB points) 12 Hz to 50kHz
Frequency response  
Input sensitivity 1.2V RMS for rated output (adjustable)
Input impedance 75 kOhms, nominal at maximum gain
Output taps  
Output regulation Approximately .8dB, 16 ohm load to open circuit
D-90B: Approximately .3dB, 16 ohm load to open circuit
Overall negative feedback 17.5dB
D-90B: 21.5dB
Damping factor Approximately 12
D-90B: Approximately 25
Distortion Intermodulation distortion: Less than .5% at 1 dB below rated output (100V p to p, 16 ohms) (SMPTE method)
D-90B: Intermodulation distortion: Less than .3% at 1 dB below rated output (100V p to p, 16 ohms) (SMPTE method)
Slew rate 20 V/µs
D-90B: 15V/µs
Rise time 2.5 µs
D-90B: 5 µs
Hum & noise Wideband, unweighted, more than 90dB below rated output
Line components, more than 80dB below rated output
Power supply energy storage 240 joules total
Power requirements 105-125VAC 60 Hz (210-250VAC 50 Hz) 800 watts maximum. 400 watts at "idle". 500 watts at rated power.
Tube complement D-90: (4) 12AX7, (2) 6FQ7, (2) 12AT7 (4 matched pairs) 6550, (1) 6550
  D-90 Revised: (4) 12AX7, (2) 6FQ7, (2) 12AT7, (4 matched pairs) 5881, (1) 6550
  D-90B: (1) 12AX7, (5) 6922, (4 matched pairs) 5881, (1) 12BH7, (1) 12AT7
Other  
Dimensions 19" (48 cm) W (standard rack panel) x 7" (18 cm) H x 16.5" (42 cm) D (front panel back). Handles extend 1 5/8" (4.1 cm) forward of front panel
Weight 64 lbs. (29 kg) Net, 80 lbs. (36.3 kg) Shipping

Reviews

Pictures

D-90:

D-90B: