Circuit Design
I designed the analogue distortion circuit topology, selecting and arranging the gain, clipping, filtering, and output stages to achieve a controllable distorted guitar tone.
Overview
As an avid guitarist, I have always enjoyed using guitar effects pedals in my playing, but purchasing high-quality pedals can be expensive. I wanted to combine my interest in guitar with my engineering background by developing my own custom pedal rather than buying one outright.
This project involved the design and construction of a fully custom analogue distortion pedal, including the circuit topology and PCB layout. The objective was to create a practical distortion circuit with controllable gain, signal filtering, and output volume that could be used on my pedalboard.
I also designed a separate test rig that can be clamped to my desk, allowing audio cables to be connected conveniently during circuit testing and evaluation. The circuit is functional and produces a distorted guitar tone, although the project is still ongoing. The next stage is to design and manufacture an enclosure, and to replace the current filter topology with a simpler low-pass filter, as I am not fully satisfied with the current filtering response.
All circuit simulations were carried out in LTspice, while the schematic capture and PCB design were completed in EasyEDA.
Gallery
Key Aspects of the Project
Simulation and Validation
I used LTspice to simulate the circuit behaviour and verify design decisions before hardware implementation, helping refine the gain and filtering response during development.
PCB Design and Assembly
I produced the schematic and PCB layout in KiCAD and assembled the circuit, including soldering SMD components and preparing the board for testing.
Test Rig Development
I also designed a desk-mounted test rig to make it easier to connect audio cables and evaluate the pedal during development, testing, and iterative refinement.
System Features
- Custom analogue distortion circuit
- Adjustable gain, filtering, and output volume
- Custom PCB designed in KiCAD
- LTspice simulation prior to hardware build
- Functional distorted guitar output
- Desk-mounted cable test rig for evaluation
- Prototype assembled and tested in hardware
- Ongoing refinement of enclosure and filter stage
Technical Skills
Analogue Audio Circuit Design
Transistor Biasing
Small-Signal Gain Stage Design
Op-Amp Configuration
Diode Clipping Design
Filter Design
PCB Design
Grounding and Decoupling
Noise Minimisation
Power Supply Design
Soldering SMD Components
LTspice Simulation
Testing and Debugging
Oscilloscopes and Multimeters
EasyEDA
Project and Development Skills
Independent Project Development
Problem Solving
Iterative Design
Prototyping
Testing and Refinement
Documentation
Technical Communication