Revox A77

(Revox A77 MK I - 1967)

This recorder is a masterpiece of electronic and mechanical engineering. The electronic function and motor control system certainly sets a new standard in deck design and performance which, coupled with the really high fidelity electronic performance, puts this new range of REVOX recorders in the connoisseur class.
(From HI-FI Sound Magazine, February 1968)

The REVOX A77 is an open reel tape recorder designed to fill the needs of the serious audiophile and the professional industry. It is a maximum performance machine that offers everything we believe to be value for use in the living room and for on-location recording, most importantly, uninterrupted recording time with convenience and ease of use, and maximum electronic and mechanical performance.

Detailed below are performance and convenience characteristics being offered for the first time in a tape recorder of this price.
(From a Revox brochure - 1972)


The Historical Background of Revox tape recorders

Willi Studer and his Revox tape recorder have gained an en enthusiast following reminiscent of the veteran car era and such names as Bugatti, Bentley and Duisenberg. His machines have been characterised by their advanced design, precision engineering and by their clean dynamic sound; the result of low distortion and wide frequency response.

The first machines, designated T26 ware made in 1949. Many still operate today and are already valued as collector's items - a distinction that few electronic products can claim. The T26 continued until 1955 when the 36 series was introduced, and with it the international recognition of Revox as the tape recordist's recorder.

As production increased, so new marked areas could be supplied and by 1967 distribution was functioning on a worldwide basis. However, even with fife factories Revox has barely adequate production and marketing has to remain restrained or demand would soon outstrip the production capability which is dependent on skilled craftsmen. The Revox is still largely handmade.

Parallel with the development of the Revox line, the Studer range of machines was created for broadcasting and master recording purposes. Studer machines are now used almost exclusively throughout Europe in the respective fields of studio work and are known as the standard by which others are judged.
(From a Revox brochure - 1972)

The A77 tape recorder is perhaps the panzer of open reels. It is very heavily built and well designed. It is a 3 motor machine, with both capstan and reel motors being direct drive, so the only belt is a counter belt. These are large reel capable and record and play in only one direction. Revox strove for performance and reliability rather than bells and whistles like auto reverse and such. The A77 came in quarter track or half track and could be ordered with various speed configurations, the most common being 3 3/4 ips (9,5 cm/sec) and 7 1/2 ips (19 cm/sec), though machines with 1 7/8 ips (4,75 cm/sec) or 15 ips (38 cm/sec) capability do show up. These have very few electronic failures, so the most important components to be sure of on one of these is how much headwear there is and the condition of the brake hubs and bands. They have an optical auto stop which requires an incandescent bulb, which sometimes burns out. If an A77 is found with little wear, but with much time elapsed since last service, they need the usual restoration work minus the belt and tire replacement required by certain other machines. After such work is done, they are very reliable and perform beautifully. Parts have generally been expensive but available in our recent experience. This machine is a very good performer in home, and has the durability to put up with heavy or professional use if desired.
(From an unknown writer on an Ebay auction - February 2001)

ReVox A77 MK versions overview


A77 - version MK I
Serial-No. S 054 - S18 080 produced 08.1967 to 06.1969
Serial-No. G 100 - G 19 368 produced 10.1967 to 06.1969

A77 - version MK II
Serial-No. S 18 081 - S 31 000 produced 06.1969 to 06.1970
Serial-No. G 19 369 - G 54 600 produced 06.1969 to 08.1971



A77 - version MK III
Serial-No. S 45 640 - S 72 852 produced 08.1971 to 08.1973
Serial-No. G 55 000 - G 145 099 produced 08.1971 to 08.1974

A77 - version MK IV
Serial-No. G 145 100 - G 289 836 produced 08.1974 - 10.1977

the "S" at the beginning of the serial No. means "Made in Schwitzerland";
a "G" means "Made in Germany"

The Revox A77 Taperecorder has been produced between 1967 and 1977 in nearly 290000 exemplars. The basic version of the A77 has been more ore less unchanged in all these years. 

Þ The Revox A77 MK I tape recorder

Þ The Revox A77 MK II tape recorder

Þ The Revox A77 MK III tape recorder

Þ The Revox A77 MK IV tape recorder

Þ The Revox A77 Dolby B tape recorder

Þ The Revox A77 professional tape recorders




Tape Transport

Three Studer eddy current motors. Electronically governed capstan motor. Electronic speed change. Solenoid operated via 3 relays.

Tape Speeds:

3.75 and 7.5 ips (9,5 cm and 19 cm/sec.) 0.2%
High speed Version: 7.5 and 15 ips (19 cm and 38 cm/sec.) 0.2%

Wow and Flutter:

max. 0.04% at 15 ips
max. 0.08% at 7.5 ips
max. 0.1% at 3.75 ips (Weighted at DIN Standard 45507)

Tape Slip:

Less than 0.2%

Reel Diameter

Maximum 10.5" (26,5cm)
(Minimum hub diameter 23/8 inches)

Forward / Rewind

Fast winding time for 1800' (1100m) is 92 seconds

Tape Heads

Three (Separate precision erase, record and playback heads.) Patented 'True Radius' design ensures excellent S/N ratio and head wrap

Guide System:

The Heads, the capstan drive, and the machines tape guides are mounted to a one-piece casting to maintain precise alignment.

Operating position:

horizontal or vertical




Individual stereo record and playback heads with separate preamps, plus separate record and play circuits permit full source-tape monitoring.


NAB Standard on both record and playback at all speeds.

IEC Standard switchable on playback only.

Record Playback
Frequency Response:

(Based on Revox 601)

15 ips - 30 Hz - 20 kHz 1.5 dB
7.5 ips - 30 Hz - 20 kHz + 2 / - 3 dB
3.75 ips - 30 Hz - 16 kHz + 2 / - 3 dB

Signal to noise:

15 ips - better than 66 dB
7.5 ips - better than 66 dB
3.75 ips - better than 63 dB

15 ips - better than 62 dB
7.5 ips - better than 62 dB
3.75 ips - better than 59 dB

Add 4 dB to the above figures with Dolby on, referenced to less than 2% THD
(Reference with Scotch 203 or Revox 601 or equivalent. Weighted as per CCITT C-curve to exclude supersonic bias noise.)

Distortion at full modulation
at 1 kHz:

Max. 2% at 15 ips and 7.5 ips.
Max 3% at 3.75 ips.

Crosstalk at 1 kHz:

Stereo, better than 45 dB
Mono, better than 60 dB

Bias frequency:

120 kHz, push-pull oscillator. Designed for low noise, high output tapes

Input sensitivity per channel

Microphone, switchable LOW/HIGH
LOW: 50 - 600 ohms (unbalanced) 15mV
HIGH: up to 100 K ohms 2.5 mV
RADIO: 33 K ohms 2.5 mV
AUX: 1 M ohms 33 mV

Output per channel

OUTPUT: max 2.5 rms @ 600 ohms
RADIO: max 1.2 rms @ 2.5 K ohms
PHONES: 200 - 600 ohms (no electrostatic)

Semiconductor complement:

54 Transistors; 32 diodes, 4 silicon rectifiers, 1 CdS-cell

Remote control:

Fully electric for all operation functions.

Output Amplifiers:

Plug-in optional. 2 x8 watts continuous rms power, 2 x10 watts music power as per IHFM, 4-16 ohms, less than 1% distortion.

Power Supply:

Electronically stabilized.

Mains voltages:

110, 130, 150, 220,240, 250V / 50-60 Hz.

Power consumption:

70 ... 100 watts

(Wooden Cabinet)

161/4" W x 141/8" H x 81/2" D.
(Measurements include knobs but not reels.)


Approximately 34 pounds ( 15 kg)

All figures quoted are minimum performance values as measured with REVOX 601 tape normally exceeded by all units.


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