This circuit was designed to obtain a valve-like distorted sound from an electric guitar or other musical instrument.
For this purpose a very high gain, three-FET amplifier circuit, was used. The output square wave shows marked rounded corners, typical of valve-circuits when driven into saturation.
Input sensitivity: 30mV RMS.
Output square wave: 6V peak-to-peak max.
Total current drawing: about 1mA.
Circuit set-up using oscilloscope and sine wave generator:
Connect a 1KHz sine wave generator to J1 and the oscilloscope to J2.