This crystal or galena radio was found in documentation from the 1990s. The earpiece must be a high impedance crystal or magnetic earpiece and D1 can be any germanium diode.
This circuit came out in an American magazine that no longer exists. It's the Electronic...
This circuit originally came out in a Budget Electronics from 1981. The American magazine no...
This is the traditional audio preamp configuration with the National Semiconductor LM382. The...