We found this circuit in an English publication in 1976. The circuit is based on the use of a germanium transistor as a current source. The circuit has a pass-through range of 16 to 4,000 Hz.

We found this circuit in an English publication in 1976. The circuit is based on the use of a germanium transistor as a current source. The circuit has a pass-through range of 16 to 4,000 Hz.