JBL SG520 268,000yen(around the 1970 time)

Control amplifier which did not use any rotated type thumb but consisted of only straight line type controls and push-button switchpoints.

Although the model number has not changed from the early model to the second-half model, the enhancement is added to the internal circuitry.

If a 1kHz testing tone oscillator is built in and the relay control F22 is combined with this, it is possible to perform the stereo sound-volume balance control called Aural Null Balancing System.

Although a front is an aluminum panel, there is SE520E which can change supply voltage by SG520G of the gold panel set by finish of power amplifier SE400S, and an expert model. 

Form	Stereo control amplifier
Output	3V
Frequency band	20Hz - 20000Hz
Input sensitivity	Phono:6mV AUX:300mV
THD	0.15
Tone control	High region: 20kHz and +21 -17 dB Low-pass: 20Hz, ±17dB
An attached circuitry	Loudness control With an NULL BALANCE

Posted in: JBL, JBL-Amplifier, JBL-Amplifier-Control