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 speakersare 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 790

Will Studer developed the revolutionary Revox b790 true tangential tracking turntable. It replaces the conventional tonearm and all its problems with a unique, patented opto-electronic playback servo-system. The cartridge moves up, down and laterally guided by a beam of light. It's easy on your record grooves and easy on your nerves. It's so simple and goof-proof even a child can safely play your most treasured records.

The new revox B790 looks and performs better than any turntable you've ever seen or heard. ...

The Revox B790 record player with quartz-controlled direct drive and tangential pick-up arm was not just exciting because of its advanced design but because of a complete range of functional innovations. The B790 united security and simplicity of operation and essentially offered new solutions to old problems.

The B790 features adjustable speed over a '7% range and a four-digit LED indicator which displays the measured rate of rotation, but otherwise the two models are the same. The tonearm design provides straight line (tangential) tracking which maintains a constant lateral tracking angle and thereby reduces certain forms of playback distortion, since record masters are always cut with tangential heads. Distortion due to skating is said to be eliminated by this design as well. Another goal of the Revox design was for the moving system to have very low effective mass. This was achieved by hanging the cartridge from a horizontal rail system. The "arm" on which the cartridge is mounted is just four centimeters long and its dynamic mass is claimed to be only 3.75 grams.

The Revox system is sold at present with either an Ortofon or an AKG cartridge. Users can buy a kit which facilitates the installation of other cartridges. Tests by Revox have shown that the fundamental resonance of this arm with most cartridges lies between 10 and 11 hertz where it would not readily be stimulated either by record warps or recorded audio signals.

The arm and cartridge are guided along the rail system by a small motorized carriage. A block assembly which contains these rails and the carriage, arm, and cartridge is then pivoted in much the same way as a conventional tonearm. To put on or to remove a record, one sets the block assembly into its "at rest" position out of the way of the platter. And to play a record, one sets the assembly over the record's surface into a detent with a claimed repeatability of ± 0. 01 mm! This starts the turntable motor, but the stylus stays lifted above the record's edge until the user presses a button to lower it. While it is lifted, cuing can be accomplished with two other push buttons.

As a record is played, the carriage is propelled forward in response to signals from an ingenious optical and electronic system. Time constants of the system are chosen so that the arm moves smoothly, and so that an eccentric groove is tracked about in the center of its range of excursion. (The back-motion is absorbed by the free-swinging arm, not the servo. )

The little tonearm has only one point of contact with the motorized carriage, a jeweled bearing which forms the lower pivot point. The vertical shaft of the tonearm is held captive by the field of a small, oblong, concave, permanent magnet. This magnet keeps the arm from rocking laterally, yet adds no friction to the system.

The mechanical suspension for the overall turntable system has its basic resonance at or below 3 Hz, rendering it quite insensitive to feedback even if it is set directly atop a subwoofer cabinet. This was demonstrated.

The dustcover, which is transparent and removable, is contoured such that it can be opened or closed even when the turntable is placed flush against a wall, and is sprung to "stay put" in any position. All operating controls are outside the locus of the dustcover.

Specifications

Turntable drive: Quartz-controlled direct drive

Speeds: 33,33 and 45 rpm, crystal accurate

Speed accuracy: ±0,01 %

Speed indication: 4-digit LED readout, quartz precise

Manual fine adjustment: ±7%

Platter diameter: 313 mm (12,32 inch)

Platter weight: 1,1 kg (2 lbs 7 ozs)

Run-up time: better than 2 sec. at 45 rpm

Braking time: better than 1,5 sec. from 45 to 33,33 rpm

Wow and Flutter: better than 0.05 % (weighted); 0,1% (unweighted)

Signal-to-noise ratio: better than 65 dB

Rumble to signal ratio:

A weighting: better than 48 dB

A weighting +20 Hz high-pass: better than 51 dB

Bweighting: better than 68 dB

Transmission characteristic for rumble measurement: Replay response -3 dB at 20 Hz

Tonearm: Linear tracking tonearm with servo electronic follow-up control

Tangential tracking angle error: less than 0.5 degrees

Tracking force: adjustable of 5... 20 mN (0.5... 2 p)

Tonearm lowering: electronically controlled, pneumatically damped

Muting: electronically muted, until the stylus contacts the record

Tonearm follow-up: Opto-electronic sensing with LED as light source, servo-electronics and DC motor

Run-out switch: automatically activated via servo-electronics

Operating controls:

Turntable drive:

3 tactile feedback keys for 33,33 and 45 rpm as well as for variable speed operation

Tonearm:

3 tactile feedback keys for fast inward or outward movement plus lowering and lifting of the pick-up cartridge; cartridge illumination built-in

Automatic functions:

Swinging the tonearm support in: Platter stsrts to rotate at the selected speed

Swinging the tonearm support out:

Immediate lifting of the cartridge

Tonearm returns to start pposition (run-in groove of a 12 inch disk)

Electronic braking of the platter

Components: 29 ICs, 30 transistors, 24 diodes, 1 LED, 4 seven segment displays and 3 bridge rectifier

Power supply: 100/110/120/200/220/240 V, 50/60 Hz

Dimensions (W x H x D): 452 x 142 x 382 mm (17,8 x 5,6 x 15,03 inches)

Weight: 11 kg 924 lbs 4 ozs)

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