This old fashioned transistor amplifier was found in a publication of the year 1958. Transformer are the critical components in the circuit and power comes from 6 D cells.
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...