This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
This is the traditional configuration of an AC amplifier using the 741 integrated circuit. I found...
This article is old, from 1994. But, for those who have an old PC and want to use a joystick from...
This simple circuit indicates when the two channels of stereo equipment are balanced. The diodes can...