This circuit was found in American documentation from 1966, but it can be assembled with a modern equivalent transistor. The circuit is based on a mechanical tuning fork with a coil feedback system.
Found in a Popular Electronics from the 90s, this theremin is played by the position of the hand...
The frequency of this circuit can be programmed by a control voltage. The control circuit is CMOS...
This preamp was found in an old English publication. Any usage JFET can be employed. The output is high...