Revox A77 Dolby

REVOXA 77 MK III - DOLBY B (click to enlarge)

Special version REVOX Dolby A 77 Tape Recorder containing entirely new Dolby B circuits to achieve the ultimate in noise reduction: even the softest pianissimo can be free of tape noise.

Even the best professional tape ,recorders have their dynamic range limited by tape hiss. This hiss may take on a high nuisance value during quiet passages or when low level sounds are present, especially if slower tape speeds are employed with quarter track tape width. Furthermore, this hiss level increases in tape dubbing with each subsequent copy of the tape. However, by applying a new electronic process developed by Ray Dolby, the inherent tape hiss can be rendered inaudible. In conjunction with the excellent recording and playback

characteristics of the REVOX-namely no hum, no clicks, no wow or flutter outstanding recordings of highest possible dynamic range are easily attained. Soft passages become even more dramatic, standing out against a perfectly quiet background.

Þ Revox A77 Critic's Choice

Þ Operating Instructions for the Revox A77 with Dolby B System

The A 77 Dolby B System

In contrast to recorders with switchable Dolby processors, the REVOX Dolby A 77 employs separate record and playback processors in each channel Containing 39 Transistors alone for the Dolby noise reduction processors,

Dolby encoded multiple transfers and off tape monitoring becomes possible without restrictions or compromise. In operation, the low level medium and high frequencies are boosted in the record processor with subsequent complementary attenuation during playback. This results in an appreciable reduction of tape hiss. Dolby circuitry in tape recording has achieved considerable popularity of late. However, only in the REVOX Dolby A 77 has the incorporation been so simplified that the sole adjustment required by the user is the setting for individual tape efficiency. In addition,

a switchable MPX- filter is provided to suppress interference when recording stereo FM broadcasts. By simple operation of a switch any A 77 Dolby will operate like a standard machine. A point to note on the Dolby model is that the spooling motors cannot be switched off. Further, it is not equipped with power amplifiers and the equalization characteristics are permanently set to the NAß standard. The specification reflects the improved signal to noise performance while all other data are the same as that for the A 77 MK III standard version.

Revox B77 MK IV with Dolby B

(click to enlarge)

REVOX A77 with Dolby Noise Reduction System, Additional Technical Data
All mesurements taken with Revox 601 tape. Dolby electronics switched on.
2-Track Version (values for the 4-Track Version are shown in parenthesis)

Signal to Noise Ratio
off tape, weighted as per CCIT

At 7 1/2 ips. better than 67 dB (65 dB)
At 3 3/4 ips. better than 64 dB (62 dB)

Signal to Noise Ratio
weighted as per ASA A

At 7 1/2 ips. better than 70 dB (67 dB)
At 3 3/4 ips. better than 67 dB (65 dB)

measured off tape, 500 Hz peak Level
(assumed to be +6 VU)

At 7 1/2 ips. better than 1% (1.5%)
At 3 3/4 ips. better than 1.5% (2%)

Operating Levekl 0 dB (100%)

At 7 1/2 ips. better than 0.5% (0.5%)
At 3 3/4 ips. better than 0.5% (1.5%)

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