This circuit from the 60's uses germanium transistors of the time. Listening is done on high impedance headphones.
This circuit was found in a 1963 publication. Its purpose is to test general purpose NPN and PNP...
This circuit provides a pulse train of 4 MHz or at another frequency determined by the crystal during...
TL series and CA3140 operational amplifier can be used in this bass and treble control circuit. We found...