What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Revox B 77

A well designed tape transport mechanism will not distort mechanically. It is insensitive to shocks and vibrations and will retain these qualities over a wide range of temperatures. Therefore, REVOX B77 tape recorders use diecast parts for the motor chassis, the side bearers, the crossmember and for the head block and the pinch roller arm. This ensures exceptional stability for the precision tape guiding system and the sound heads, as well as for the motors and the brake assembly. The motors are sturdy AC asynchronous types - unbeatable in simplicity and reliability - thus especially suited for heavy duty use.

Magnetic tape recorders are an outstanding example of the perfect combination of precision mechanics and top performing electronics. Even the best electronic circuitry would soon become worthless if the original precision in tape guiding is lost as a result of insufficient long term stability. One of the basic requirements, therefore, is to ensure stable performance for years with a rigid mechanical design which disregards the possible advantages that may lie in 'such tempting advertising claims as 'feather weight' and "slim line?!

Speed control via servo electronics

In 1967 STUDER REVOX had already ushered in the age of electronic capstan speed control for domestic tape recorders. Ever since then many have tried to copy it yet they have never been able to match its simplicity and effectiveness. The principle of electronically regulating a sturdy asynchronous motor by means of a separate precision reference has stood the test so well that it has been adopted for the STUDER professional tape recorders years ago. The capstan motor and its precision reference combined with the inductive speed sensor and its control circuits form a regulating loop which is highly insensitive to variations in power line voltage and frequency or changes in load. This system, which has proven its reliability in more than half a million tape drives, combined with ideal tape guiding results in outstanding motion stability (freedom from wow and flutter which remains unchanged for years. The remarkable mechanical and electronic stability of the complete tape transport mechanism makes it well suited for mobile operation by powering from car batteries in conjunction with an inverter.

For pitch matching or to achieve special effects, motor speed can also be varied continuously over a wide range with the help of an external speed control. The Revodur all metal heads for recording and playback, the erase head, the infrared tape sensor and the tape guides; all these components are mounted on a rigid die-cast frame. A fourth magnetic head can be fitted to record automatic slide synchronizing control signals (DIA/DHA/FH). These signals are recorded within the guard band of the tape allowing their use with normal stereo signals. As far as development of magnetic sound heads is concerned, STUDER REVOX is looking back on an experience which equals that of building tape recorders. Our experts manufacture all metal heads for REVOX B77 tape recorders and for professional sound recorders. The special alloy Revodur ensures excellent magnetic properties and outstanding wear characteristics. The shape of the head's face is designed to ensure a "ruler flat" response down to the lowest audio frequencies. Ease of editing

The practical edit facility is standard equipment on each Revox B77 recorder. By operating the sliding button, the tape is brought into contact with the heads, the playback amplifiers become activated and the fast wind buttons respond only as long as they are held depressed. This facilitates motor assisted searching for the edit point while final tape positioning is then performed manually. The thoughtful design of the lower control panel facilitates easy access to tape heads for accurate tape marking. An ingenuously conceived edit mode facilitates motor assisted tape shuttling and final manual locating of the exact edit point. B77 versions

Part of the B77 head block, showing the roller bearing tape guide and infra red tape end detector. The integrated tape cutter helps to make editing a simple task. Track configurations: Half track (S2):

Half track models are always selected when tape splicing (editing) is required. Because of the large track width of 2mm, these models feature excellent ratings with respect to frequency response and treble dynamic range. The half track version can be equipped with slide control electronics and an additional sound head. The high-speed version of the half track machine is ideally suited for applications requiring maximum audio quality (e.g. as effects machine in audio or film production). The quarter track (S4): The advantage of quarter track machines over half track machines is the double tape capacity. The quarter track B77 is suited for applications where long playing times (up to six hours on the standard speed B77) combined with excellent audio quality is essential. The quarter track machines can also be equipped with side control electronics and an additional sound head. Because of the narrower track width, the audio specifications are in certain areas slightly inferior to those of half track machines. The quarter track configuration interleaves the two stereo tracks. This allows the reels to be "turned over" allowing double the recording time The half track configuration uses the full width of the tape to lay down a stereo image. (excluding the guard band) Standard version of B77

Direct drive capstan motor with tacho generator and servo electronics to ensure outstanding speed stability independent of variations in load or changes in the electrical supply voltage or frequency. Magnetic tape recorders are an outstanding example of the perfect combination of precision mechanics and top performing electronics. Even the best electronic circuitry would soon become worthless if the original precision in tape guiding is lost as a result of insufficient long-term stability. One of the basic requirements therefore, was to ensure Revox B77 stable performance for years, achieved with a rigid mechanical design, which disregards the possible advantages that may lie in such tempting advertising claims as "feather weight" and "slim line"! Precision cannot be realized without ruggedness. This is the reason why all important parts of the B77 transport mechanism are made from solid die-castings. Speed control via servo electronics

Tape transport mechanism:

Three motors; 2 AC reel motors; 1 AC capstan motor, electronically regulated

Tape speeds:

9,5 and 19 cm/s, electronic switching, speed accuracy ±0.2%

6,5 and 28 cm/s external speed variation

Wow and flutter (DIN 45507):

At 9,5 cm/s <0.1%,

At 19 cm/s <0.08%

Tape slip: Maximum 0.2%

Reel size:

Up to 26,5 cm (10.5”) diameter, minimum hub diameter 6 cm (2.36”)

Tape tension switchable for small hub diameters

Rewind time:

Approximately 135 seconds for 1100 m (3,600 ft) of tape

Tape transport control:

Integrated control logic with tape motion sensor provides for any desired transition between different operating modes. Electronic motor control (without brushes); all functions can be remote controlled

Equalization (NAB):

9,5 cm/s (3.75 ips): 90/3180 microsec

19 cm/s (7.5 ips): 50/3180 microsec

Frequency response (measured via tape at -20 dB VU):

9,5 cm/s (3.75 ips): 30 Hz - 16 kHz +2, -3 dB and 50 Hz - 10 kHz ±1.5 dB

19 cm/s (7.5 ips): 30 Hz - 20 kHz +2, -3 dB and 50 Hz - 15 kHz ±1.5 dB

Max. recording level: 514 nWb/m corresponds to +6 dB VU

Level metering:

VU meter to the ASA standard, with LED peak level indicators


9,5 cm/s (3.75 ips): <1% (0 dB VU, 257 nWb/m); <2,5%, (6 dB VU, 514 nWb/m)

19 cm/s (7.5 ips): <0,6% (0 dB VU,257 nWb/m); <2%, (6 dB VU, 514 nWb/m)

Signal to noise ratio (ASA A weighted):

Half track

9,5 cm/s (3.75 ips) >63 dB

19 cm/s (7.5 ips) >69 dB

Quarter track

9,5 cm/s (3.75 ips) >60 dB

19 cm/s (7.5 ips) >63 dB

Crosstalk (at 1 kHz):

Stereo >45 dB,

Mono >60 dB

Erase depth: >75dB at 19 cm/s (7.5 ips)

Inputs per channel:

Mic Low: 0.15 mV/2,2 kΩ for 50 - 600 Ω impedance microphones

Mic High: 2.8 mV/220 kΩ for high impedance microphones

Radio: 2.8 mV/20 kΩ

AUX: 40 mV/1M Ω

Outputs per channel (Level at 6 dB VU, 514 nWb/m):

Output: 1.55 V/390 Ω

Radio: 1.55 V/4,7 kΩ

Phones: 5.6 V/220 Ω

Connectors for:

Remote control mechanism

Remote control of variable tape speed

Slide projector or crossfade unit (electronics optional)


11 ICs, 1 opto-coupler, 4 triacs, 60 transistors, 33 diodes, 5 LEDs, 2 full wave rectifiers, 3 relays

Electric current supply:

100 - 240V 50/60 Hz

Voltage selector for 100V, 120V, 140V, 200V, 220V, 240V

Maximum consumption power: 80 watts

Main fuse 120V 1A slow-blow, 240V 0.5A slow-blow

Dimensions (W x H x D): 452 x 414 x 207 mm

Clearance required for 10.5” reels height 464 mm, width 538 mm

Weight: Approx. 17 kg

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