Revox A77 Tape Recorder the magnetic recording masterpiece of our time (1967), and they're still going strong today!
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.
Since 1949 the Willi Studer Company have distinguished themselves by their dynamic advances
in magnetic recording equipment for the broadcast and recording industries. The all-new REVOX A77
is therefore unique in possessing studio breeding. Significant mechanical and electronic advantages
resulting from this experience are clearly evident throughout the machine. Featured here is the wood
surround version, available either with or without the optional plug-in 8 Watt per channel audio power
amplifiers. Also available is the suitcase model which incorporates four high definition loudspeakers
providing built-in stereo or mono monitoring and playback to a standard hitherto unknown in an all-in-one unit.
The REVOX A 77 will make and replay tapes to professional standards. Indeed thousands of Revox A77 machines
are used world wide for this purpose. An LP disc of outstanding quality can be cut from a carefully made
REVOX recording and the performance of the machine is a match for the finest audio equipment available
today. All facilities required in modern recording techniques are catered for, including sound on sound, multi-play,
echo, on-off tape monitoring as well as playback to both European and American equalization standards. Further,
the REVOX A77 will operate both horizontally and vertically and can accommodate even 10.5 inch diameter tape
spools. The use of relays and solenoids permits all tape transport functions to be operated by remote control,
including going, into the record mode.
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.
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. Revox A77 Only with three motors is it possible to provide each of the 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 A77 tape recorders all over the world.
The speed of the new capstan motor is no longer governed by the mains frequency as in the case of the usual synchronous
or non-synchronous motors. The speed of the motor is measured by means of a tacho head which does not touch the moving
parts and kept constant by means of the electronic governor. The new motor will run at an extremely constant speed
independent of the mains frequency.
With the development of an electronically governed capstan motor REVOX have once again pioneered in the field of
magnetic recording. The new motor is smaller, lighter and has a much lower current consumption and considerable
reserve power. Furthermore, the speed constancy is completely independent of the normal mains frequency and voltage fluctuations.
The change in the motor revolution: for the two tape speeds of 7 ips and 3 ips. 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.
The rigid die-cast head block holds three stereo heads. Two of them, the separate record and replay heads, are all-metal
professional heads. These high quality heads were specially developed for the REVOX tape recorder A77 These heads are
the result of valuable experience, which we gained in the construction of all-metal heads for studio tape recorders.
The tradition of quality at the REVOX works is based on several decades of experience in the manufacture of high quality
tape recorders. Our experienced engineers and technicians have advanced the fundamental concepts of tape recorder design
in the development of the new REVOX A77. In addition they have developed a matching range of high fidelity units which are
capable of making full use of the performance of the REVOX A77 thereby providing the discriminating music lover or professional
user, with a complete system of unparallel excellence. The system comprises a high power HI-FI amplifier of 2 x 40 Watts with silicone
planar transistors throughout. A supreme FM - tuner with ' field effect ' input stage and integrated IF circuit designed to give the highest
quality stereo FM reception, even under the most difficult conditions.
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 are heavily gold plated over a hard nickel skin. This process has already
proved highly successful in our transistorised studio machines Revox A77.
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.
It is a pleasure to report that the widely acclaimed, but no longer available, Revox G-36 Mk III tape recorder has actually been surpassed in
performance by Revox's new Model A77.
The A77 has fully solid-state electronics, a bias-oscillator frequency of 120 kHz (as opposed to 70 kHz for the G-36), and a new electronic
motor-speed control. The A77 model we tested is a three-motor, four-track, two-speed recorder; however, it is substantially lighter and
smaller than its predecessor.
The Revox A77 has its operating controls grouped into separate recording and playback areas. On the playback side there are two rotary
switches with concentric knobs. One switch establishes the playback mode - stereo, either channel through both outputs, or both channels
combined for mono. It's concentric knob controls playback level. Revox A77 other switch connects either the signal input or the signal output to the
playback amplifiers (before/after tape monitoring) routed to the output jacks on the rear of the deck. Two playback equalization characteristics
are provided: NAB or IEC (for European tape recordings). The recording equalization is to the NAB standards. The knob concentric with this switch
is a playback channel balance control.
On the right side of the recorder panel are two VU meters with real VU-meter characteristics. Adjacent to each is a red button of the push-on,
push-off type. Depressing either channel's button alone records both inputs on that channel. If both buttons are depressed, a stereo recording is
made. These supplement a record-interlock button, providing a double safety against accidental tape erasure. Recording levels may be set up
before the tape is put into motion. When the Revox A77 is in operation in the recording mode, the selected channel's VU meter (or meters) is illuminated.
Under each meter is a recording input-selector switch with a concentric recording-level control. There are inputs for high and low-impedance
microphones (with front-panel jacks in parallel with rear phono connectors), radio (via a rear DIN connector), and auxiliary inputs with connectors
in the rear. In addition, each switch has a position for recording the output of that channel combined with any additional source on to the other
channel (multi tracking).
The transport mechanism is operated by a row of five pushbuttons, activating relays to control fast speeds, stop, play and recording. A connector
in the rear permits the use of an accessory remote control unit for these functions. The tape speeds (7 and 3 ips) are selected by a switch
that also controls a.c. power to the recorder. Each speed setting has two switch positions that set the tape back-tension to optimum values for
either 10 inch or smaller reels.
The servo-controlled drive system of the Revox A77 is unique and effective. An eddy-current motor that delivers a high torque, free of the
pulsations that are inevitable with any motor having a pole structure, powers the tape-drive capstan. The speed of this motor can be adjusted
by varying a d.c. control voltage, with relatively little torque variation. The motor has a built-in tone generator that produces an a.c. signal whose
frequency is proportional to motor speed. This signal is amplified, limited, and applied to a discriminator, whose d.c. output is proportional to speed.
This is further amplified and used to correct the motor speed. The change between 7 and 3 ips is accomplished electronically by shifting the
resonant frequency of the discriminator circuit. The chief advantages of this technique are independence from power-line voltage and frequency
variations, as well as reduced flutter. Flutter of the A77 motor is inherently so low that the capstan can be driven directly from the motor shaft instead
of through a separate belt-driven flywheel. According to the manufacturer, line voltage fluctuations of +/-20% cause a speed change of only +/-0.05%,
and a change in the a.c. line frequency of 50 to 60 Hz also causes a speed change of less than 0.05%. Thus, the Revox A77 is a truly universal machine,
capable of operating from 110 volts to 240 volts, simply by adjusting a switch at the rear of the recorder regardless of either a 50 or 60 Hz supply.
When the full-width head cover is swung down, two more pushbuttons are revealed. One cuts off the signal to external speakers, and the
other switches off the power to the reel motors. This Revox A77 "tape dump" facility is for convenience in editing. When the reel motors are turned off,
and the recorder placed in a fast speed mode, the reels may be turned by hand with the tape in contact with the playback head. At the desired point,
the tape may be lifted from the heads and placed in the tape splicing guide which is molded into the fixed portion of the head cover. The only problem
with this arrangement is the possibility that one may spill tape by forgetting to turn on the reel motors before placing the machine back into normal operation.
We stated that the A77 surpassed the older G-36 in performance. This is best illustrated by its phenomenally flat record/playback frequency
response of Revox A77, measured with Scotch 203 tape, for which the machine's bias was adjusted. At 7 ips, the response was within + 0.5, - 2.0 dB from
20 to 20,000 Hz. This has never been equalled by any other recorder we have ever tested. Perhaps even more impressive is the response at 3 ips,
which was + 2.5 - 5.5 dB from 20 to 20,000 Hz. The high end falls off smoothly and is perfectly usable all the way to 20,000 Hz. The NAB playback response,
with the Ampex 31321-04 test tape, was+ 1.5, - 0.5 dB from 50 to 15,000 Hz.
The signal-to-noise ratio was very good, 51 dB at 7 ips and 48.5 dB at 3 ips, referred to a 0-VU recoding level. Noting that the distortion
at 0 VU was a mere 0.65%, we increased the recording level until a more typical distortion level was achieved, approximately 3%, which occurred
at +10 VU for the higher tape speed and +9 VU for the lower speed. At these levels Revox A77, the signal-to-noise ratio was increased to 59 dB at 7 ips
and 54.5 dB at 3 ips, figures that closely approach true professional performance.
The transport worked smoothly and with complete silence. Except for the turning of the reels, one could not tell the machine was operating
from a distance greater than about 12 inches. Wow was 0.01% (actually the residual inherent in our instruments) and flutter was 0.09% at 3 ips
and 0.07% at 7 ips. In fast speeds 1,800 feet of tape was handled in about 90 seconds, and the machine could be brought to a stop in about 2
The Revox A77 is housed in a teak cabinet with a foldaway carrying handle. It is one of the handsomest, as well as best performing, tape
recorders we have ever seen. We have never seen a recorder that could match the performance of the Revox A 77 in all respects, and very few
that even come close. It sounds as good as it tests, which speaks for itself. The Revox A77 is offered in a variety of configurations. It is available
with either half or quarter track heads, in either the teak cabinet or a portable carrying case.