Revox A77 MKIV

The Revox A77 MKIV is the final and most refined version of the legendary A77 reel-to-reel tape recorder series, produced between 1967 and 1977 in Switzerland and Germany. It retains the core mechanical design that made the A77 famous while incorporating minor improvements and refinements to enhance reliability and audio performance.

Mechanical and Transport Features

• Transport Mechanism:
  The MKIV uses the classic rugged 3-motor system with two reel motors and one electronically regulated capstan motor. This direct-drive design eliminates belts and clutches, reducing mechanical wear and ensuring stable tape speed and gentle tape handling.

• Tape Speeds:
  Supports two standard speeds: 3¾ ips (9.5 cm/s) and 7½ ips (19 cm/s).

• Tape Format:
  1/4 inch (6.35 mm) tape, 2-track stereo configuration.

• Reel Size:
  Compatible with reels up to 10.5 inches (26.5 cm).

• Braking:
  Solenoid-operated servo brakes provide smooth and positive stopping even from high winding speeds.

• Durability:
  The die-cast motor chassis and head support provide mechanical precision and long-term stability, even with heavy use.

Electronics and Audio Performance

• Equalization:
  NAB equalization for recording, with selectable NAB or IEC equalization for playback.

• Frequency Response:
  Approximately 30 Hz to 20 kHz (±2/3 dB) at 7½ ips, matching original factory specifications.

• Signal-to-Noise Ratio:
  Around 62 dB, typical for professional tape decks of its era.

• Total Harmonic Distortion:
  Approximately 0.6%.

• Output Power:
  8 watts output, suitable for driving external amplification or monitoring.

• Input/Output Levels:
  Line input sensitivity around 35 mV; line output approximately 1.2 V.

• Meters:
  Equipped with VU meters, though noted to have some sensitivity variance between channels in original units.

Physical Specifications

• Dimensions:
  415 x 359 x 180 mm.

• Weight:
  Approximately 15 kg (33 lbs).

Additional Notes

• The MKIV is known for its warm, rich sound and sleek appearance, making it one of the best consumer tape decks of its time.

• Its simple yet effective transport mechanics have been carried forward into later Revox models like the B77 and PR99.

• Restored units often feature upgraded capacitors and lubricants to maintain optimal performance.

• The MKIV is a 2-track deck, focusing on stereo playback and recording.