by Max Kingston
Project Overview
Distortion is the amplification and clipping of an input signal in a musical context. Clipping is the elimination of certain parts of the sound wave which makes it sound more distorted. This pedal circuit is designed to add fullness to the input signal with a simple phase chorus, amplify and clip with two stages of gain, and provide a variety of possible sounds with tone and volume knobs.
Tools and Materials
- 2x 47 µF
- 8x 10 kΩ
- 2x 100 pF
- 2 kΩ
- 2x 47 nF
- 4.7 kΩ
- 2x 100 kΩ Potentiometer
- 2x LM358 Op-Amp
- 3x 22 nF
- 2x 1 MΩ
- 1000 nF
- 83 pF
- 1 µF
- 680 kΩ
- 1 kΩ
- 2x LED Diode
- 2x 220 Ω
- N5457 JFET
- 10 kΩ Potentiometer
- LF411 Op-Amp
- 20 kΩ
- 2x quarter inch jack holders
- 2x quarter inch cables
- A violin pickup (for example, the Band2 or other piezo pickup)
- A violin
- A practice amplifier (or set of speakers)
Project Files
Step-by-Step Instructions
Construct the first section of the circuit, for audio signal input and filtering. This part takes the input signal from the violin, filters out frequencies above the human hearing range, and floats the signal above ground to avoid unnecessarily losing negative signals through the op amps later.
Construct the second part of the circuit, the simple phase chorus. The the capacitor helps to shift the waves slightly. Since the resistors connected to the negative op amp terminal are the same, the signal is not amplified at all.
For this third part, build the first gain stage, including a knob to adjust the amount of gain. C6 can be adjusted to change the amount of low frequencies that are amplified and distorted, and chaning C7 will adjust the amount of high frequencies that are amplified and distorted.
Now, construct the second gain stage. This includes diodes to clip the signal.
Finally, add two potentiometers to control first tone and then volume. Tone control is like volume, but frequency dependent. Then, we build a buffer to help filter the output signal slightly before a speaker can be connected to the output of this step.
