Revox A77 Dolby B

The Revox A77 Dolby B version is a special edition of the classic A77 reel-to-reel tape recorder, introduced around 1972, featuring integrated Dolby B noise reduction circuitry to significantly reduce tape hiss and improve dynamic range during recording and playback.

Mechanical and Transport Features

• Tape Speeds: 7½ ips (19 cm/s) and 3¾ ips (9.5 cm/s), electronically governed capstan motor with electronic speed change.

• Motors: Three motors – one electronically regulated capstan motor and two reel motors.

• Wow and Flutter: Maximum 0.08% at 7½ ips, 0.1% at 3¾ ips.

• Tape Reel Size: Supports reels up to 10.1 inches (26.5 cm).

• Operating Position: Can be used horizontally or vertically.

Audio and Electronic Features

• Frequency Response:
  At 7½ ips: 30 Hz to 20,000 Hz (+2/-3 dB)
  At 3¾ ips: 30 Hz to 16,000 Hz (+2/-3 dB)

• Distortion (Full Modulation, 1000 Hz):
  Max 1.5% at 7½ ips
  Max 2% at 3¾ ips (with Dolby B engaged)

• Signal-to-Noise Ratio:
  Better than 58 dB at 7½ ips
  Better than 56 dB at 3¾ ips (with Dolby B)

• Noise Reduction: Dolby B noise reduction system with separate record and playback processors per channel, allowing multiple tape transfers and off-tape monitoring without compromise.

• Equalization: NAB standard for recording and playback; Dolby B version primarily uses NAB equalization with Dolby calibration tone for setup.

• Calibration: Dolby calibration controls enable precise adjustment for tape formulation and recording level, ensuring optimal noise reduction performance.

Construction and Components

• Heads: Three heads (erase, record, playback).

• Amplifiers: Modular design with plug-in output amplifiers capable of 2 × 8 watts continuous RMS power.

• Power Supply: Electronically stabilized for consistent performance.

• Remote Control: Fully electric remote control for all operational functions.

• Additional Features:
  Reduced brake tension for easier editing in STOP mode.
  Modified tape-monitor switch to include NAB equalization and Dolby calibration tone.
  Premagnetization and erase frequency at 120 kHz for low noise and high output.

Physical Specifications

• Dimensions: Approximately 16¼ in (W) × 14¾ in (H) × 8¾ in (D) (over controls)

• Weight: About 34 lbs (15.4 kg)

• Power Output: Optional plug-in amplifier delivering 2 × 8 watts RMS per channel at 8 Ω.