This wired control circuit serves both volume and balance between channels. We found it in Radio Electronics magazine from August 1968. Transistors are common general-purpose types
This circuit consists of a small inverter that can generate a few hundred volts of DC voltage...
The use of a detector bridge instead of a single diode, as is normally done in common galena...
The LM150, 250 and 350 series of 3 A are manufactured by several semiconductor industries that...