ReVox A77 version MK I Reel-to-Reel Tape Recorders, serial-no g003444, 1967, made in Germany

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Revox A77 (MK I to MK IV), Tape recorder (1967-1977) revox

The launch of the Revox A77 marked the start of the company's most successful tape recorder range. The first sales brochure was entitled "Tradition and Progress" and didn't just present a new tape recorder but a hi-fi line that also included an amplifier and an FM tuner.

The company's experiences in the construction of tape recorders since 1949 and the development of a completely new approach based on the stable silicon planar technology, enabled the company to break new ground. Pluggable terminal amplifiers made the direct connection of two loudspeakers possible. The German designer Manfred Meinzner was involved in the new development and he ensured that the complete line had a concise appearance.

The A77's complete drive was mounted on a stable, torsion-free die-cast chassis. To give added stability, the motor mounting, recording head block and even the side walls were also die-cast. The A77 could also be used standing vertically, without any restrictions. Of course, it had a 3-motor drive. The really special feature was the capstan motor. The robust asynchronous motor was true pioneering work. As a worldwide innovation it was not just smaller, lighter and much less heavy on energy consumption. Its speed consistency was also independent of fluctuations in mains power frequency and voltage levels. The secret was an electronic speed controller that could handle both 50 Hz and 60 Hz (USA) operation without any adjustment.

For the first time, a tape recorder aimed at the amateur market had professional, all metal recording heads. The complete "solid state" electronics were mounted on pluggable printed circuit boards making service very easy. Drive control was done through free-moving pulse push buttons and the relay control not only enabled the remote control of all functions but it also meant that it was protected electrically against incorrect operations.

The A77 featured calibrated VU meters, a photoelectric tape end switch, a four-position tape counter and a controllable, stereo headphone output. It also included take-up motors that could be switched off, a special cutter button for tape splicing as well as a wide range of trick options. A comprehensive, illustrated User manual, the "Red booklet" soon became a textbook for budding recording engineers.

Many different versions appeared during the ten years that the Revox A77 was produced. Even the first brochure listed five versions of each of the 2 and 4 track devices. In addition, there were special radio station versions, e.g. the A77-PTI and the A77-ORF. Of particular interest was the version with integrated Dolby™ B System, which delivered an impressive 70 dB signal-to-noise ratio, (19 cm/s, 2 track, ASA-A Standard) with a distortion factor of better than 1% at full power or better than 0.5% at 0 VU power (185 n/Wb/m).

In the January 1969 edition of the North American specialist magazine "Stereo Review", the authors from the Hirsch-Houck Laboratories call the servo-controlled drive system "unique and effective", and describe the frequency response as "phenomenal" and come to the telling conclusion: "We have never seen a recorder that could match the performance of the Revox A77 in all respects, and very few that even come close".

In 1978, the Japanese specialist magazine "Audio Specialist", awarded the Revox A77 1st prize as the best "non-Japanese reel-to-reel tape machine".



REVOX PERFORMANCE SPECIFICATIONS
FOR REVOX A77 MK I / REVOX A77 MK II / REVOX A77 MK III / REVOX A77 MK IV



Mechanical
Tape TransportThree 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 DiameterMaximum 10.5" (26,5cm)
(Minimum hub diameter 23/8 inches)
Forward / RewindFast winding time for 1800' (1100m) is 92 seconds
Tape HeadsThree (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
Electrical
MonitoringIndividual stereo record and playback heads with separate preamps, plus separate record and play circuits permit full source-tape monitoring.
Equalization: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:2-Track:
15 ips - better than 66 dB
7.5 ips - better than 66 dB
3.75 ips - better than 63 dB
4-Track:
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 channelMicrophone, 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 channelOUTPUT: 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
Dimensions:
(Wooden Cabinet)
161/4" W x 141/8" H x 81/2" D.
(Measurements include knobs but not reels.)
Weight:Approximately 34 pounds (» 15 kg)
All figures quoted are minimum performance values as measured with REVOX 601 tape normally exceeded by all units.