This old configuration of an audio amplifier has a push-pull two-transistor output stage. Output power is low and the critical components are the transformers. The circuit was found in an 1958’s publication.
Found in an American 1980s documentation, this circuit makes use of a sensor of the era uncommon...
This interesting configuration of optical triggering using an oscillator was found in a 90s...
This headphone amplifier has good gain and high input impedance. The circuit is from Electronics Now and...