This 5-tube hi-fi amplifier was found in an American publication from 1947; The output is in class B and the circuit uses a source with transformer.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...