reel-to-reel tape

Revox B77

Revox has a long history, developing audio systems for more than 60 years. In the beginning, Dr. Willi Studer produced tape recorders. Revox B77 (and also Revox A77) are milestones in audio history.

Revox launched a completely new hi-fi range in 1977 including Revox B77 reel-to-reel tape deck. However, no significant differences were between the B77 and its predecessor A77 but B77’s drive and control system was more sophisticated. The B77 was also equipped with a splicing block. B77 had a large number of special versions, fortunately including a high-speed version B77-HS with 19/38 cm/s as well.

What are the best features of Revox B77?

Revox B77 chassisPrecision Transport

For long-term stability and performance, a successful tape transport system requires a stable chassis. To balance the required stability and a weight compatible with home use, Revox B77 has a sturdy aluminium die-casting for the chassis, head block, pinch roller and mechanism.

Precision Three-Motors Drive

Studer-Revox manufactures its own special drive and winding motors. The Studer motors and controls are of the reasons these tape decks are widely acknowledged. To reduce wow and flutter, the direct-drive capstan shaft is machined to an accuracy of one one-thousandth of a millimetre, is hard chrome-plated and is artificially aged during the manufacturing process to ensure long-term stability. The direct drive capstan motor with tacho generator and servo electronics produced outstanding speed stability that is almost independent of variations in load or changes in the electrical supply voltage or frequency. 

Precision Heads and Electronics

Revox B77 headsThe head cores are made from a hard but magnetically soft metal alloy called Revodur that has nearly perfect electromagnetic qualities. Heads were built to the same standard of Studer professional studio decks.

Three-Head Monitoring

The record and playback heads of the B77 are separate units. You can monitor the recorded result simultaneously, making a direct comparison between the original and recorded signal.

Precision Editing Facilities

Revox B77 headsA splicing block (which is really one of the best I know) and a non-magnetic cutter are built into the front panel of the B77, allowing tape editing. In addition, a lever switch is also included that activates the playback amplifiers during the fast-winding modes. In this way, you can quickly shuttle back and forth between fast forward and rewind to find the exact point at which a cut is to be made. For critical cuts the reels can be rotated manually while the tape remains against the playback head.


What makes the Revox B77 so appealing is that it shared much with their Studer-badged professional siblings, so it is more rugged than most. Sonically, B77 is among the most domestically-acceptable reel-to-reel machines. Regarding price and dimensions B77 might be the best home open-reel tape recorder.

Servicing of Revox B77

Like any other vintage open-reel tape recorders, Revox B77s may also have suffered the damages of time and wear. You should check the electronics, and also the mechanical elements that might need replacing. Do not forget about the tape heads because their wear is always a primary concern. The first part of the service is making sure that the machine is safe and replacing all parts that are known as weak points, as their failure can damage other parts of the machine.

Revox B77 headsMechanical parts

First get the machine’s transport working correctly; that means the tape should run at the correct speed and tension. This will usually involve lots of cleaning, replacing belts, brake linings, and adjusting control circuit components. Correct tape tension and smooth running are absolutely essential with any tape based recording device from a cassette deck to studio mastering machine.

Electronic parts

The audio circuits should thoroughly be tested. Very few machines work as they should without a few component changes. All electrolytic capacitors and tantalum capacitors need to be replaced by high-quality, low noise and low distortion audio capacitors and optimized with foil bypass capacitors again. Trimmers need to be replaced with encapsulated ones. We also replace old transistors to low noise transistors and also replace op-amps. All printed circuit boards, plug contacts, potentiometers and switch contacts are thoroughly cleaned.

Electrical adjustments and alignments

Alignment means head alignment, replay gain and EQ, record gain, EQ and bias. Without a reliable test and alignment tape (for each speed and EQ), you are not in the position to align the heads and replay circuitry. Although it is not hard to align a tape machine's electronics if you have the appropriate equipment and the necessary knowledge. Otherwise, you will need to go to a specialist with your tape recorder.

Revox B77 headsHere is a short list of adjustments:

  • Checking the supply voltage
  • Tacho head adjustment
  • Tape speed calibration
  • Demagnetizing
  • Checking the gain of the input amplifier
  • VU meter calibration and checking the overload indicators
  • Frequency response 'before tape' measurement
  • Reproducing head azimuth adjustment
  • Reproduction level adjustment (0,775V) from calibration tape
  • Reproducing system frequency response measurement
  • Checking oscillator frequency and RF voltage
  • Adjustment of bias trap
  • Recording head azimuth adjustment

Calibration and alignment of Revox B77 for a specific tape and speed

  • Bias adjustment
  • Recording level adjustment
  • Adjusting the recording equalization
  • Overall frequency response measurement

The above calibration should be repeated for any tape type and tape speed.

You may get all tools, parts and even calibration tapes at the great shop of Nagravox.

How to buy a good Revox B77?

You may find a lot of Revox/Studer B77s on Ebay or any other advertisement places. You should always check the condition of the tape recorder which is not easy by looking the pictures of the advertisement. Buy from a secure source where you can be sure that the machine is in a good condition and it was properly serviced and aligned.