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 speakers are 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

JBL SG 520

 A perfectionist's instrument, featuring unparalleled flexibility of inputs, outputs, mixing, and professional linear actuated controls, the Graphic Controller offers the flatest frequency response, lowest distortion, lowest noise level and greatest operating convenience of any preamplifier. Additional controls, tape monitor switch and convenience inputs and outputs are located behind special hinged front panel.
 Special Features:
Professional linear-actuated controls allow precise adjustment and give instant visual recognition of exact settings. Illuminated push-buttons permit instantaneous switching from any function to any other function. Seledom-used controls are concealed behind a hinged lower panel, out of sight when not needed, yet directly accessible from the front.
Included in the secondary control bank are output level set controls, gain controls for both phono inputs, high frequency filter, low frequency filter, tape monitor witch, and an auxiliary "trim" balance control for the phono input. (Whit this, the residual unbalance in any particular pickup cartridge can be eliminated without disturbing normal settings for other program material) the hinged panel also conceals input and output jacks for convenient connection of temporary auxiliary equipment.
 Aural Null Stereo Balancing System
By adding the F22 remote relay (available as an accessory), the Graphic Controller becomes more than a fine stereo control center ,  it can be used as a sensitive instrument for balancing channels and checking the performance of your stereo component installation.
(All specifications are measured with AC line voltage of 117 volts at 60 cycles. Line voltage fluctuations between 105 and 127 volts do not affect the performance at the Graphic Controller.)

Output:  3 Volts (more than sufficient to drive a JBL Energizer or any conventional power amplifier)
Frequency Response:  Typical response is within ¼ dB through the entire audible range from 20 - 20,000 cps. (the smallest deviation which can be detected by the human ear is approximately one dB.)
Distortion (these are typical specifications under ambient temperatures which would normally be encountered in a home installation):
Total Harmonic Distortion  (at full rated output):  less than 0,15% at any frequency from 20 - 20,000 cps
Intermodulation Distortion:  less than 0,05% at 3 volts output
Hum and Noise:  1 mV or less referred to the low level phono input. From high level inputs, noise is 90 dB below rated output.
Low level inputs:  54 dB
High level inputs:  2 dB (require 0,3 volts for rated output)
Tone Controls:
Treble :  17 dB boost or cut at 20,000 cps
Bass :  21 dB boost or cut at 20 cps
Control Tracking Accuracy: 
Through their full range of operation, the linear actuated controls of the Sg-520 exhibit variations typically less than one decibel from laboratory specifications. This means that you enjoy the unlimited flexibility of continuously variable controls, yet with a degree of tracking accuracy normally obtainable only with individual calibrated switch-type attenuators.
Tempearature Stability:
The SG-520 is considerably less sensitive to temperature changes than ordinary transistorized preamplifiers. So long as sufficient ventilation is provided to keep air temperature in its immediate vicinity below 110° F, it can be left on indefinitely without affecting the quoted specifiactions.

Dimensions (W x H x D):  15-9/16" x 6-1/2" x 13"

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