P1______________10K Log. Potentiometer R1_______________1M 1/4W Resistor R2_______________3K3 1/4W Resistor R3_______________2K2 1/4W Resistor R4_______________5K 1/2W Trimmer (Cermet) R5_____________100K 1/4W Resistor C1,C4__________100nF 63V Polyester Capacitors C2_____________100pF 63V Ceramic Capacitor C3,C5___________22µF 25V Electrolytic Capacitors Q1,Q2,Q3______2N3819 General-purpose N-Channel FETs J1,J2__________6.3mm Mono Jack sockets SW1_____________DPDT Toggle - Slider or Pedal Switch SW2_____________SPST Toggle or Slider Switch B1________________9V PP3 Battery Clip for PP3 Battery
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.
Therefore, the distorted sound obtained from such a device has a peculiar tone, much loved by most leading guitarists.
- 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.
Adjust R4 until the output square wave shows equal mark-space ratio.
"By ear" circuit set-up:
Connect a musical instrument to J1 and an amplifier to J2.
Carefully adjust R4 in order to obtain as maximum output sound intensity as possible.