audio research
D-79

Description
Tube stereo power amplifier.

Introduced
1979

Discontinued
?

Revisions
D-79A
D-79B (1981) (Only 80 made)
D-79C (Around 25-30 made)
D-79C MKII

Options
-

MSRP (US new retail)
D-79: $3,250. Later increased to $3,700
D-79B: $3,950. Later increased to $4,450.
D-79C MKII: $6,000

Specifications

Power output 75 watts per channel minimum RMS (both channels operating) at 16 ohms from 30Hz to 15kHz with less than 1% THD. (Typically approximately .1% (D-79C: .06%) at rated power in midband) Approximate actual power available per channel at “clipping“ (Both CH. OP, 1kHz): 87 Watts.
Power bandwidth (-3dB points) 15Hz and 40kHz
Frequency response  
Input sensitivity .75 V RMS for rated output
Input impedance D-79: 80K ohms, nominal
  D-79C: 75K ohms, nominal
Output taps  
Output regulation D-79: Approximately 1.5dB, 16 ohm load to open circuit
  D-79C: Approximately .6dB, 16 ohm load to open circuit
Overall negative feedback D-79: 13.5dB
  D-79C: 18.5dB
Damping factor D-79: Approximately 8
  D-79C: Approximately 15
Distortion Intermodulation distortion: Less than .5% at 1dB below rated output (90V p to p, 16 ohms) (SMPTE method)
Slew rate Approximately 10 V/µs
Rise time 5 µs
Hum & noise Wideband, unweighted, more than 90dB below rated output. Line components, more than 80dB below rated output.
   
Power supply energy storage  
Power requirements 105-125/210-250 VAC, 50/60Hz, 750 watts maximum, 350 watts at “idle“, 550 watts at rated power
Tube complement D-79: (6)12AX7, (8) 6FQ7, (2 matched pairs) 6550, (1) 6550
  D-79B: (1) 6922, (4) 12AX7,(2) 6FQ7, (2 matched pairs) 6550,(1) 6550, (1)12BH7
  D-79C: (9) 6922, (2 matched pairs) 6550 (1) 6550, (1) 12AT7, (1) 12BH7
  D-79C MKII: (3) 6922, (6) 6FQ7, (2 matched pairs) 6550, (1) 6550, (1) 12AT7, (1) 12BH7
Other  
Dimensions 19“ (48 cm) W (standard rack panel) x 10 ½“ (26.5 cm) H x 17 ¼“ D (front panel back). Handles extend 1 5/8“ (4.1 cm) forward of front panel.
Weight D-79: 89 lbs. (41 kg) Net, 107 lbs. (49 kg) Shipping
  D-79C: 85 lbs. (38.8 kg) Net, 100 lbs. (45.7 kg) Shipping

Reviews

Number 18 (D-79: Full Review), Number 25 (D-79B: Full Review), Number 26 (D-79B: Further Thoughts)

Pictures

D-79B:

D-79C: