Revox A77

The Revox A77, produced from 1967 to 1977, is a landmark reel-to-reel tape recorder renowned for its robust engineering, reliability, and audio fidelity. Nearly half a million units were manufactured, making it one of the most successful and respected tape decks in both professional and high-end consumer audio circles.

Mechanical Design and Transport

• Transport System:
  The A77 features a three-motor transport mechanism: two reel motors and one electronically regulated capstan motor. This design ensures gentle tape handling and minimal mechanical wear, contributing to the machine’s longevity and suitability for archival work.

• Chassis:
  A die-cast motor chassis and head support provide mechanical precision and long-term stability, even under heavy use.

• Braking:
  Solenoid-operated servo brakes and DC braking offer fast, smooth operation and precise tape control.

• Reel Capacity:
  Supports reels up to 10.5 inches (26.5 cm) in diameter, with adapters for smaller reels.

• Counter and Detection:
  Equipped with a mechanical tape counter and a photoelectric end-of-tape detector.

Electronics and Circuitry

• Modular Construction:
  The electronics are built with plug-in transistor panels, making servicing and maintenance straightforward.

• Components:
  Utilizes 54 transistors, 32 diodes, 4 silicon rectifiers, 1 photoresistor, and 4 relays.

• Inputs/Outputs:
  Line input: 35 mV
  Microphone input: 0.15 mV
  Line output: 1.2 V
  Optional amplifier modules were available, though most units are tape deck only.

Tape Speeds and Audio Performance

• Standard Tape Speeds:
  9.5 cm/s (3¾ ips)
  19 cm/s (7½ ips)
  Some versions support 38 cm/s (15 ips).

• Wow and Flutter:
  0.08% at 19 cm/s (7½ ips).

• Frequency Response:
  30 Hz – 20 kHz (+2/-3 dB) at 19 cm/s
  30 Hz – 16 kHz (+2/-3 dB) at 9.5 cm/s.

• Signal-to-Noise Ratio:
  Up to 66 dB (2-track, 19 cm/s)
  Up to 64 dB (4-track, 19 cm/s)
  Improved by 1 dB with Dolby noise reduction.

• Total Harmonic Distortion:
  0.6%.

• Crosstalk:
  45 dB