This circuit was found in Sgnetics documentation from the 80's. The circuit also has loudness control. The power supply must be symmetrical.
This small general purpose and RF transistor tester appeared in a February 1958 Radio Electronics...
The MC4741 integrated circuit consists of four operational amplifiers similar to the 741 in a...
We found this touch control on a Popular Electronics from 1970. The circuit makes use of an...