REVOX A77

Professional Tape Recorders

Rugged 3-Motor Tape Drive

with its 3 motors on a solid die-cast chassis, the A77 possesses the basic design features of a professional tape recorder. Due to the direct drive principle, there are no friction wheels, clutches or belts needed. This makes for a mechanically simple drive system with only a few movable parts. Thus, wear is reduced to a minimum, a point of vital importance for the long life of a tape recorder.

Electronically Regulated Capstan Motor

Uniform motor speed - and with it even tape motion - does not rely on utilizing the power line frequency, but is controlled instead by an internal electronic regulating system. Tape speed is thus stable and to a high degree independent of any variation in power line voltage or frequency. Therefore, the A77 may also be used by driving it from batteries (via an inverter with sine wave output) and nothing whatsoever has to be changed when moving from a 50 Hz to a 60 Hz electric supply area or vice versa. The change of tape speed is also achieved electronically, free of any mechanically wearing parts, and free of any influence on the characteristics of the tape drive mechanism.

Electronic Control of Tape Drive Functions

All functions of the tape drive mechanism are controlled by a simple relay logic. This makes possible soft "finger touch" switching, as well as remote control of all operating modes. Solenoid activated servo-brakes ensure safe and positive stopping of the tape even from the highest winding speed.

REVODUR Sound Heads

The REVODUR sound heads have improved magnetic characteristics and a much higher life expectancy. Consistent quality is thus assured since STUDER REVOX designs and builds their own magnetic heads.

Exact Calibration

Separate calibration controls for each speed and channel permit precise bias and equalization adjustments of the A77. This forms the basis for the excellent recording characteristics of all A77 recorders, because our published specifications are minimum values, which must be met by each and every recorder.

A77 Professional Inputs

The A77 professional recorder is available in 7 ½/15 IPS half & full track configuration and is fitted with Cannon XLR connectors on inputs and outputs. Inputs are balanced, line level and require +8dBM for full tape modulation. The input levels are preset and no front panel adjustments are provided. The outputs have independent line amplifiers providing a balanced +8dBM preset line level. In addition an adjustable output is provided to feed headphones or unbalanced equipment. Optional plug in 8 watt amplifiers are available for the half track machine to drive external speakers or the 4 internal speakers included in the suitcase version. Specifications

Line: balanced; sensitivity +8dBM (preset for full modulation; Cannon XLR3 connectors.

A77 S. L. S.
(Super Low Speed)

The A77 is available ina super low speed of 15/16 & 1-7/8 IPS. With the A77 super low speed 15/16 IPS version Revox reliability is now available for all logging applications. Over 12 hours can be recorded in one pass on two tracks, with 3,600 feet of tape. With a modification to the end of tape lamp circuits, two machines can be linked to provide automatic logging for 24 hours.

The S. L. S. model combines mechanical simplicity and proven reliability with a very reasonable cost. A true alternative to complex and costly loggers.

The A77 S. L. S. is available in half and quarter track formats.

A77 Autostart (Vox)

The A77 Autostart machine automatically goes into the record mode in the presence of a signal. It will continue to record for up to 7 seconds (variable) after the signal has been removed and then stops. (Trigger sensitivity is variable for each channel). The A77 Autostart is ideal for any operator unattended monitoring application where good recording quality (7½ IPS) is required. For example Radio stations can use this Revox machine to receive network news feeds automatically. Security firms who must record telephone calls can do so backed up by Revox dependability.

The A77 Autostart has the same fine specifications as the regular model 11102 (a push for Manual button disables the auto start circuitry for normal operation) and is available in quarter and half track formats at 3¾ and 7½ IPS. All figures quoted are minimum performance values as measured with REVOX 601 professional tape.

Tape Drive Mechanism Design principle:
3-motor tape drive mechanism, electronically regulated servo capstan motor

Tape speeds: 3¾ and 7½ ips, selected by electronic switching. Deviation from nominal ±0.2%
Wow and flutter: weighted,
at 7½ ips, less than ±0.08%
at 3¾ ips. less than ±0.1%

Measured in accordance with IEEE standard 193-1971 (consistent with DIN 45507)

Tape slip: not exceeding 0.2%

Tape reel dimension: up to 10½" outside diameter (minimum hub diameter 2 3/8 ")

Uninterrupted playing time:
with long playing tape 3600 feet, 3 hours 12 mins. at 3¾ ips. 1 hour 36 mins. at 7½ ips

Operating positions: horizontal, vertical or inclined. Remote control: momentary contact switching for all functions

Electronics
Semi Conductor Complement: 54 transistors, 32 diodes. 4 silicon rectifiers, 1 light dependent resistor. 4 relays

Amplifier: plug-in printed circuit boards

Frequency response: measured via tape at 7½ ips.
30-20,000 Hz ±2/-3dB
50-15,000 Hz ±1.5 dB
at 3¾ ips.
30-16.000 Hz +2/-3dB
50-10.000 Hz ±1.5 dB

Equalization: recording as per NAB*, playback as per NAB* or IEC (switchable)
•(consistent with DIN 45513/H)

Distortion: measured via tape at 1 kHz peak level and 0 VU respectively at 7½ ips, less than 2% or 0.6% respectively
at 3¾ ips, less than 3% or 1% respectively

Signal to noise ratio: measured via tape,
weighted as per ASA - A:
at 7½ ips, better than 66 dB
4-track better than 62 dB
at 3¾ ips, better than 63 dB
4-track better than 59 dB

Crosstalk: at 1000 Hz for monophonic operation, better than 60 dB, stereophonic operation, better than 45 dB

Oscillator frequency: 120 kHz (push-pull oscillator)

Overload margin for each input: 40 dB

Inputs per channel

Microphone (switchable for high and low impedance microphones): Sensitivity for 50-600 ohms low impedance microphones: 0. 15 mV. maximum 15 mV
Input impedance 2. 2 k ohms

Sensitivity for high impedance microphones up to 100 k ohms: 2. 5 mV. maximum 250 mV. Input impedance: 220 k ohms
Input connectors RCA-phono sockets and phone jacks
Radio: sensitivity 2.5 mV. maximum 250 mV, input impedance 33 k ohms
Input connector 5-pin DIN socket

Auxiliary input: sensitivity 35 mV, maximum 3. 5 V,
input impedance 1 M ohm
Input connectors RCA-Phono sockets

Outputs per channel

Output for amplifier: maximum output voltage 2. 5 V. source impedance 600 ohms
Output connector RCA-phono socket
Output for radio: maximum output voltage 1.2 V, internal impedance 2. 5 k ohms
Output connector 5-pin DIN socket
Output for headphones: recommended load impedance 200 ohms or higher, volume adjustable
Output connector phone jack

Power output stages: optional plug-in amplifiers, all performance characteristics conform to DIN 45500
8 watts continuous average power per channel, measured with a load impedance of 8 ohms at a maximum total harmonic distortion of 1%. Loudspeakers having a nominal impedance of 4 to 16 ohms may be connected.

Loudspeakers (2 per channel in the suitcase model) will be automatically disconnected when plugging external loudspeakers into the respective DIN output sockets.

Power requirement: electronically regulated power supply.

Operation on 50 to 60 Hz power line without the need for change-over. Power consumption without power stages 70 W approximately, with power stages 70 to 100 W. fuse rating.
110 to 150V: 1 amp, slo-blo

Weight: approximately 33 pounds

Model variations: walnut cabinet or metal case with or without power amplifiers, suitcase model with built-in loudspeakers, 2-track or 4-track version
Technical Specifications (General)

With 26.5 cm (10.5 inch) reels (all models), max. width 539 (21.22), max. height 442 (17.40).


STUDER INTERNATIONAL AG
CH-8105 Regensdorf, Switzerland
Althardstrasse 150
Phone 01 8402960
Telex 58489stuich

Other important advantages of the new REVOX tape recorder A77 are calibrated VU-meters, a photo-electric end-of-tape switch, a four-digit tape position indicator and a separate output for stereo headphones with its own volume and balance controls. Facilities for switching off the spooling motors and a special button for tape editing.

3 MOTOR TAPE TRANSPORT SYSTEM

The new REVOX A77 employs the classic three motor tape-transport system. The recently developed capstan motor drives the tape at constant speed.

Two further motors provide back tension from the feed spool and a constant take-up tension for the take-up spool. Furthermore, these motors, which are of original low weight-high torque design, permit a very smooth and fast tape wind. Only with three motors is it possible to provide each of the tape drive functions with the optimum characteristics. The same applies to the electro-magnetically operated servo-assisted brakes, which have proven themselves in the professional studio machines, as well as in previous REVOX.

ELECTRONICALLY GOVERNED CAPSTAN MOTOR

With the development of an electronically governed capstan motor REVOX have once again pioneered in the field of magnetic recording. The new motors are smaller, lighter and has much lower current consumption and considerable reserve power. Furthermore, the speed constancy is completely independent of the normal mains frequency and voltage fluctuations.

ELECTRONIC SPEED CHANGE

The change in the motor revolution: for the two tape speeds of 7 1/2 ips (19 cm/sec) and 3 3/4 ips (9,5 cm/sec) is effected by means of the electronic governor. The speed change is effected by means of one single low current switch ensuring high reliability and long life.

SILICON PLANAR TRANSISTORS

are used throughout the series A77. The types used are all metal cased thus ensuring maximum stability and long life. Where condenser values are critical tantalum has been chosen. All the amplifier electronics are built on plug-in printed circuit boards. The contacts do not have the usual tinned coating, but ere heavily gold plated over a hard nickel skin. This process has already proved highly successful in our transistorised studio machines.

The cable connections between the individual sub-assemblies are also made via plugs and sockets. Although an expensive method of construction we can thereby guarantee high reliability and serviceability. The electronic stabilisation of the supply voltage to the amplifiers and the oscillator make the performance of the machine independent of mains voltage fluctuations. Together with the electronically governed capstan motor this ensures important advantages when driving the machine from a battery by means of vibrators or rotary converters.