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The Studer ReVox B77 open-reel recorder retains the advantages of the A77, eliminates limitations of the earlier models, and adds features of its own. (The A77 remains in the product line, at least for the time being.)

The frontpanel styling of this high-class audiophile recorder is similar to that of the professional A700 model.

Interlocked push-button switches select speed, 3 3/4 or 7 1/2 ips. Below are the large-handle toggle switches for power and monitor selection and paralleled jacks for headphones.

This can be a handy feature at times, providing a front-panel output in addition to one for a set of phones. The level at these jacks is controlled by a dual-section, slip-clutch pot, which does not affect the regular line outputs on the back panel.

The output selector switch, however, does affect all outputs including metering, and can be set for stereo, reverse stereo, left channel to both outputs, right channel to both outputs, and mono which combines the two channels and feeds the mix to all jacks.

The choices provided with this switch facilitate a number of tasks without the need to change connections and use adapters. The smooth-acting input level pots have knobs of a good size, an improvement over those on the A77.

Alongside are the record presets with a large status light above each switch, illuminated when the recording process starts. The large toggle handles are convenient, but were judged to be subject to inadvertent switching.

The input selector switches have positions for both low- and high-impedance single ended microphones, Radio (DIN), AUX, and for feeding in the output of the other channel for sound-on-sound recording.

Mike inputs are standard phone jacks, and it might be noted that mike/line or other mixing is possible, if recording is done on just one channel.

Studer ReVox claims for superior head design are graphically illustrated with the extended low-frequency response with just the slightest indication of head contour effects, superb performance.

Similar plots were made using Memorex Quantum at 3 3/4 ips (Fig. 2). At reference level, response was from 20Hz to 13kHz. At the -20dB record level, the upper limit moved out to 23.5kHz (average), but there was a peak in the response around 17kHz.

With Maxell UD at 7 1/2 ips, the responses extended further than with Scotch 206, but at the expense of excessive peaking at the highest frequencies (Fig.3).

This deviation could be reduced greatly with a slight increase in bias. The small discrepancies between the two channels could be eliminated in similar fashion. Studer ReVox, however, takes the position that bias switches or pots should not be readily accessible because of possible abuse by unqualified users.

That is a valid point, but I suspect that the more technically oriented owners will drill access holes in the bottom of the cabinet, just as many have done with the A77s.

The playback of a recorded 10kHz tone had a 30 degree phase discrepancy between channels, evidence of very good alignment between the heads.

Phase jitter at 7 1/2 ips was 15 degrees, also very good. The bias residual in the output was down into tape noise, excellent design and adjustment.

The playback of a recorded 1 kHz square wave had relatively small tilt (Fig. 4), another demonstration of the superb low-frequency response, and some short-duration ringing at the EQ peaking-frequency. Some momentary, partial dropouts appeared in the stored waveform.

Plots were made of HDL3 vs. record level for Scotch 206 at both speeds and Maxell UD at just 7 1/2 ips (Fig. 5). On a dB-dB basis, the functions were the most linear ever measured, with just a slight upturn near the 3% points.

At the low end, HDL3 continued to reduce to the noise limits of the test equipment, with little evidence of distortion in the electronics.

From 30Hz to 7kHz, HDL3 was very low, particularly at 10dB below reference level. Throughout this entire range, other harmonics were consistently very low, excellent magnetic design.

Signal-to-noise ratios with IEC "A" weighting at 7 1/2 ips were 58.7 dBA for Scotch 206 and 59.3 dBA for Memorex Quantum at reference level, and 67.0 and 70.0 dBA for the same tapes for HDL3 = 3%.

At 3 3/4 ips using the Memorex tape, the figures were 57.1 dBA at reference level and 65.2 dBA at the 3 per cent point.

All indications from test tapes and a strobe were that the recorder tape speeds were close to exact. There were no indications whatsoever of speed changes from 100 to 130 line voltage.

At 3 3/4 ips, the typical weighted peak flutter was 0.06%. At 7 1/2 ips, the flutter was 0.028% on the average, with a maximum value of 0.04% (Fig. 6).

• Anmerkung : Das sind Specs, über die wir uns hier bei uns nie Gedanken gemacht hatten, weil die Bandgeschwindigkeit über die 50Hz Netzfrequenz und dann über die Motorachse, die mechanischen Abmessungen der Reibräder oder Riemen-Umlenkrollen bestimmt wurde. In den USA schien das aber anders zu sein oder man traute den Europäern nicht über den Weg.

These results are well within the specifications and are direct evidence of superb tape motion. There were substantially no shifts in record-to-playback speed, and a slight shift plotted in one case was from drift in the metering.

The wind times for a 3600-foot 10 1/2" reel was 132 seconds. The time required to go from fast wind to play was less than two seconds at all times, smooth and fast.

Tape loading was easy and direct with little to snag the tape on, and there was good access for regular cleaning and demagnetization.

Snapping off the head assembly cover did improve access to the capstan and scrape flutter filter. There was a good feel to all of the pots and switches during all phases of the testing.

The logic-controlled, tape-motion switching performed without error, including the usual "torture" test. As stated before, a latch-in pause control did seem a definite lack at times. There was good meter action, and the placement of the overload LEDs seemed ideal in actual use.
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There were some troubles with tape motion, but the major difficulties disappeared with use. When first started in play, there was a scraping noise from the right reel turntable. Removing the front panel aided in making the tentative conclusion that some brake lining glue was rubbing against the brake band.
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The 44-page trilingual instruction book is logical and thorough with good descriptions complemented by clear illustrations.

No schematic is included, but there is an excellent signal-flow block, and circuits are given of the remote control units, so you could even make your own.
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Die Specs standen in der Beschreibung (dem Artikel) ursprünglich ganz am Anfang.

Frequency Response:
30 Hz to 16 kHz @ 3 3/4 ips,
30 Hz to 20 kHz @ 7 1/2 ips.
Harmonic Distortion:
1 per cent @ 3 3/4 ips, and
0.6 percent® 7 1/2 ips.
S/N Ratio:
59 dBA @ 3 3/4 ips,
62 dBA @ 71/2 ips.

Crosstalk: -45 dB - Erasure: 75 dB.

Input Sensitivity: Mike, Lo Z, 0.15mV, Hi Z, 2.8mV, Line 40mV. Overload Margin: 40dB
Output Level: Line 1.55V; Headphone 5.6V (open circuit) for 200- to 600-ohm phones.
Flutter: 0.1% wtd. peak @ 3 3/4 ips, 0.08 percent wtd. peak @ 7 1/2 ips.
Speed Tolerance: 0.2%
Wind Times: 135 seconds for 3600 feet.
Dimensions: 17.8" (45.2cm)W x 16.3" (41.4cm)H x 8.14" (20.7cm)D.
Weight: 37.4 lbs. (17 kg).

Price: US $ 1,295.00.