Revox A77 MKII

The Revox A77 MKII is an enhanced version of the classic A77 reel-to-reel tape recorder, produced in the early 1970s. It maintains the hallmark robustness and professional design of the original while incorporating minor improvements in appearance and electronics.

Mechanical and Drive System

• Motors: Three Papst outrunner AC motors - two reel motors and one electronically regulated capstan motor - provide precise tape transport and stable speed control.

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

• Tape Handling: Supports reel sizes up to 10.5 inches (26.5 cm). The transport uses solenoid-operated servo brakes and a die-cast motor chassis for mechanical precision and long-term stability.

• Pitch Fluctuations:
  ±0.08% at 19 cm/s
  ±0.1% at 9.5 cm/s
  Slip less than 0.2%.

Electronics

• Circuitry: Built with 54 transistors, 32 diodes, 4 silicon rectifiers, 1 photoresistor, and 4 relays, designed for serviceability and durability.

• Power Consumption: Approximately 70–100 VA.

• Signal-to-Noise Ratio:
  66 dB (2-track) and 64 dB (4-track) at 19 cm/s
  63 dB (2-track) and 59 dB (4-track) at 9.5 cm/s
  With Dolby noise reduction, improved by about 1–2 dB.

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

• Total Harmonic Distortion: Approximately 0.6%.

• Crosstalk: Around 45 dB.

Features and Design

• Heads: Three tape heads (erase, record, playback) allow for professional-quality recording and monitoring.

• Equalization: Supports NAB and IEC standards for recording and playback.

• Appearance: The MKII version features a gray lower front panel, silver scale VU meters with illumination, differing from earlier versions primarily in aesthetics.

• Dimensions and Weight:
  Size: 415 x 359 x 180 mm
  Weight: 15 kg (33 lbs).