Preamplifier stage (CB8934E)

This circuit is from a 90s Popular Electronics. It appears elsewhere on this site. Q1 can be any general purpose transistor.

Digitally controlled audio switch (CB12748E)
This circuit can serve as a basis for a digital mixer or simply for a noiseless switch of audio...
Microphone mixer (CB7988E)
This traditional mixer configuration with a high input impedance was found in a 90’s Popular...
1-transistor radio (CB20247E)
This medium wave radio works with any general purpose NPN transistor. The diode must be made of...