Audio Research D-90 Vintage Stereo Tube Amplifier - Made in the USA - 80 Glorious Watts

$1,699

Warm, musical, and engaging vintage tube amplifier from the early 1980's. Made to the highest quality standards available at the time (hand soldered and assembled).

A great survivor and amazing value.  Comes complete with its rare original box

The amp passed our battery of tests with solid results and was able to deliver just above the full rated power.  In our listening room it powered our Klipsch speakers with authority and ease.  

Click here for a copy of the D-90 Owner's Manual & Schematic

Our Testing Process for Amplifiers (Tube) at SkyFi:

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested.

We also test all tubes for output gain and leakage on our calibrated B&K 747 tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage Kef speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.

Technical Specifications:

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)

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) 
Frequency response 12 Hz to 50kHz
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

 

Item

Included

Original Box

Yes (!)

Manual

Online

Remote

N/A

Cables

Yes - Power Cable

Physical Condition

8

Working Condition

8

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