This circuit, found in a 1964 US documentation, consists of a selective amplifier that lets only 10 Hz pass around a 400 Hz center frequency with the indicated components.
This circuit with transistors was found in an old Japanese publication, translation of an American...
This 8 W amplifier with germanium transistors was found in a Japanese documentation from 1967. The...
This circuit of the 80's makes use of components of the time. The circuit is from an American...