This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent components. The transistors may be BC558 and the transformer is obtained from a disused transistor radio.
Found in ancient American documentation, this circuit uses some components from the time, such as...
A JFET is used in this circuit to maintain constant gain. The circuit is from an Electronics Now...
This very low power amplifier is designed by Amperex for hearing aids. It is based on TAA370 which is...