This circuit uses an unusual sensor nowadays, but the configuration can be adapted to more modern types, as well as the operational amplifier. The circuit is from an 80's documentation.
This circuit produces a signal that has the waveform of the sound produced by or near the banjo....
This is a circuit with a period component that consisted of a voltage reference. The circuit is...
This circuit doubles the frequency of a rectangular signal applied to its input. The circuit has a...