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Modern Distortion Effect Pedal
Pilot PCB design for a guitar distortion pedal, created as an open hardware platform for experimenting with analog distortion, overdrive-style clipping, tone shaping, relay bypass switching, off-board wiring, and enclosure-friendly pedal development.
Video
Watch the project video:
Project Overview
Distortion is a PCB-level guitar/audio effects project built around the idea of creating a practical, understandable, and modifiable analog distortion pedal.
The project is designed as a pilot hardware platform for:
  • shaping the sound of an analog distortion/overdrive circuit;
  • experimenting with clipping stages and tone filtering;
  • testing different gain, tone, and level control schemes;
  • using external potentiometers, jacks, LEDs, and footswitches;
  • adapting the PCB to different pedal enclosures;
  • improving the circuit through measurements, listening tests, and future revisions.
This is not only a distortion effect. It is also a learning and development board for understanding how real guitar pedals are built: input stage, gain stage, clipping behavior, tone filtering, output stage, power filtering, switching, grounding, connectors, and mechanical integration.

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Key idea
The PCB is intentionally designed with connectors for external wiring.
Instead of placing potentiometers, audio jacks, and the footswitch directly on the board, these elements are connected through headers or connectors and can be mounted off-board.
This decision was made because the final enclosure was not fixed during the first design stage. Using connectors gives more freedom:
  • the board can be tested on the bench;
  • the same circuit can be installed in different cases;
  • knob spacing can be changed later;
  • jacks can be placed on the side, top, or another panel;
  • the footswitch position can be adjusted;
  • the PCB can be modified without redesigning the whole mechanical layout every time.
This makes the first revision more practical as a development platform.

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Why I built this
Most guitar distortion pedals and low-cost effect modules are finished products. They can sound good, but they do not always show why they sound that way.
You turn the knobs, but the circuit remains hidden.
I wanted to build the opposite: a distortion project that can be understood, modified, measured, improved, and turned into something personal.
This is a pilot project. The goal is not to claim that this is the final perfect distortion pedal. The goal is to create a solid starting point: a working hardware base that can later evolve into different sound versions, better filtering, improved mechanical design, cleaner measurements, and a polished enclosure-ready revision.
The first version focuses on the core idea:
  • create a distortion circuit on a custom PCB;
  • keep the mechanical part flexible;
  • avoid locking the design to one enclosure too early;
  • use modern and available components where possible;
  • leave space for future improvements;
  • build something that can be tested, listened to, measured, and developed further.
For me, this project is not only about making a sound effect. It is about learning how to turn a circuit into a real device.
Design philosophy

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The philosophy of this project is simple:
  1. Build the core distortion circuit first.
  2. Keep the mechanical part flexible.
  3. Test the sound.
  4. Measure the signal.
  5. Improve the filtering.
  6. Then turn it into a finished pedal.
This first version is not meant to be the final commercial product. It is a living prototype.
It is designed to answer practical questions:
  • How does this distortion stage sound?
  • Is the gain range useful?
  • Is the tone/filter section effective?
  • Is the output signal clean enough?
  • Is the noise level acceptable?
  • Does the power filtering need improvement?
  • Which potentiometers feel better in real use?
  • Which enclosure layout makes the most sense?
  • Should the next version include one sound mode or two?

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Main features
  • Analog guitar/audio distortion circuit.
  • Connector-based design for external controls and wiring.
  • Flexible off-board potentiometer connection.
  • Off-board input and output jack support.
  • Footswitch connection support.
  • LED indicator support.
  • Power input and filtering section.
  • Suitable as a learning PCB for guitar effects and analog audio.
  • Designed as a first revision that can be measured, modified, and improved.
Why these components
The component choice is based on several practical goals:
  • use modern and available components instead of relying only on old or hard-to-find parts;
  • keep the circuit suitable for PCB assembly and future manufacturing;
  • choose stable passive components for the audio path;
  • keep the design easy to modify;
  • make the board realistic for ordering, soldering, testing, and future revisions.
For the signal path, the goal is to use components that are suitable for audio work: stable resistors, appropriate capacitors, reliable connectors, and parts that are easy to source from modern distributors.
For the control section, the design intentionally uses external potentiometers connected through headers. This makes it possible to test different potentiometer values, shaft types, knob spacing, and enclosure layouts without changing the main PCB.
For the switching and mechanical interface, the footswitch and audio jacks are also kept off-board. This gives more flexibility because pedal enclosures can have different hole positions, internal heights, wall thicknesses, and connector layouts.
This approach makes the first revision more practical as a development platform. It may not be the most compact possible layout, but it is much easier to test, modify, and adapt.
Issues Found and Next Steps
prototype-bring-up-status-issues-found-and-next-steps
Off-board connectors and enclosure flexibility
One of the key design decisions in this project is the use of connectors instead of mounting everything directly on the PCB.
The following parts are intended for off-board wiring:
  • potentiometers;
  • input jack;
  • output jack;
  • footswitch;
  • LED indicator;
  • external power connector, depending on the final enclosure design;
  • optional mode switch in future versions.

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This was done because the final pedal enclosure was not selected at the beginning of the project.
If potentiometers and jacks are placed directly on the PCB, the entire board becomes dependent on one exact enclosure, one exact drilling pattern, and one exact mechanical layout. That can be risky in a pilot project.
Using connectors gives more freedom:
  • the PCB can fit different enclosures;
  • the knob layout can be changed later;
  • the footswitch position can be adjusted;
  • the jacks can be placed on the side, top, or another panel;
  • the board can be tested outside the case;
  • future revisions can reuse the same electrical design with a different mechanical layout.
This makes the project more flexible and easier to develop step by step.
Input, output, controls, and connectors
The project is built around a flexible connector-based structure.
Possible external elements include:
  • guitar/audio input jack;
  • output jack;
  • footswitch;
  • potentiometers for sound control;
  • LED indicator;
  • power input;
  • optional mode switch in future versions.
The exact control names can be adjusted depending on the final schematic, but the project can support typical distortion pedal controls such as:
  • Drive / Gain — controls how strongly the signal is amplified and clipped.
  • Tone / Filter — shapes the frequency response of the distorted signal.
  • Level / Volume — controls the final output level.
  • Mode switch — optional future switch for different clipping or filter modes.
  • Overdrive / Distortion selector — possible future dual-mode feature.
Because these parts are connected off-board, the layout can be changed without redesigning the main circuit immediately.
Current limitations and things to improve
This is a pilot project, so several areas still need more work.
Output filtering
The output filtering should be reviewed and improved. The circuit may need a cleaner or more controlled filter stage after the distortion section to shape the final sound better and reduce unwanted harshness or noise.
Power filtering
The power filtering should be tested carefully. Distortion circuits can amplify not only the guitar signal but also power noise, grounding issues, and switching noise from external adapters.
Potentiometers
The potentiometers should be tested in real use. The final version may need higher-quality potentiometers with better mechanical feel, better tolerance, and more reliable long-term performance.
Grounding and wiring
The grounding and wiring strategy should be checked after the board is placed into a real enclosure. Off-board wiring gives flexibility, but it also requires careful attention to noise, shielding, ground loops, and cable routing.
Validation
The project still needs proper validation:
  • oscilloscope measurements;
  • input and output waveform comparison;
  • clipping behavior analysis;
  • frequency response testing;
  • noise testing;
  • audio samples;
  • real guitar tests;
  • testing with different amplifiers or audio interfaces.
Testing and validation
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This project should be validated not only by listening but also by measurement.
Recommended validation steps:
  1. Check all component values before soldering.
  2. Check polarity of electrolytic capacitors.
  3. Check diode orientation.
  4. Check IC orientation.
  5. Check power connector polarity.
  6. Inspect solder joints.
  7. Test for shorts between power and ground.
  8. Power the board with current limiting if possible.
  9. Measure the supply voltage on the board.
  10. Check current consumption without an audio signal.
  11. Inject a clean sine wave into the input.
  12. Compare input and output waveforms on an oscilloscope.
  13. Observe how the waveform changes when Gain/Drive is adjusted.
  14. Check the tone/filter response.
  15. Test noise level with no input signal.
  16. Test the pedal with a real guitar.
  17. Record audio samples for different control positions.
  18. Compare overdrive/distortion behavior if future modes are added.
Oscilloscope screenshots and audio samples will be important for the next stage of documentation.
Modern Pedal Distortion — custom guitar pedal sound created with Flux.ai
Safety and first power-up notes
Before first power-up:
  • check all component values;
  • check polarity of electrolytic capacitors;
  • check diode orientation;
  • check IC orientation;
  • check power connector polarity;
  • inspect solder joints;
  • test for shorts between power and ground;
  • power the board with current limiting if possible;
  • do not connect expensive audio equipment before the basic electrical checks are complete.
Because this is a distortion circuit, wrong wiring, grounding problems, or incorrect power connection can create noise, hum, unstable behavior, or component damage.
The first version should be tested carefully and documented step by step.
Manufacturing notes
This project is intended to be suitable for PCB manufacturing and future assembly.
The next documentation package should include:
  • schematic export;
  • PCB render;
  • Gerber files;
  • BOM;
  • component placement file;
  • assembly notes;
  • off-board wiring diagram;
  • enclosure drilling guide;
  • potentiometer wiring diagram;
  • jack and footswitch wiring diagram.
Since this version uses off-board wiring, the wiring diagram is especially important. The PCB itself is only one part of the pedal. The final device also depends on how the external controls, jacks, LED, power, and footswitch are connected.
Want to remix this?
The first version is only the beginning. There are several possible future directions.
Dual sound version
A future version could include two sound characters:
  • one softer overdrive mode;
  • one heavier distortion mode.
This could be done with switchable clipping stages, different diode combinations, different gain ranges, or a mode switch that changes the behavior of the circuit.
Overdrive + Distortion version
Instead of one fixed distortion sound, the pedal could become a hybrid effect:
  • overdrive for warmer, lighter breakup;
  • distortion for stronger, more aggressive clipping.
This would make the project more versatile and useful for different playing styles.
Improved tone/filter section
The output filter and tone-shaping section can be developed further. A better filter could make the sound smoother, reduce unwanted high-frequency harshness, or give the pedal a more recognizable character.
Future versions could include:
  • simple tone control;
  • active filter;
  • switchable filter modes;
  • bass/treble shaping;
  • mid-frequency emphasis;
  • output buffer improvements.
Better mechanical version
Once the enclosure is selected, a future PCB version could place some elements directly on the board:
  • board-mounted potentiometers;
  • board-mounted jacks;
  • fixed footswitch position;
  • LED position matched to the case;
  • compact layout for a specific pedal enclosure.
The current version keeps everything flexible. A future version can become more polished and enclosure-specific.
Measurement-focused version
Another future direction is to make the project better documented with real test data:
  • oscilloscope screenshots;
  • waveform before and after clipping;
  • frequency response graphs;
  • noise measurements;
  • audio demos;
  • comparison between diode/clipping options;
  • comparison between overdrive and distortion modes.
Who this is for
This project is for people who want to understand and build guitar/audio effects at the circuit level.
It is for:
  • guitar pedal builders;
  • electronics learners;
  • audio experimenters;
  • PCB design beginners;
  • makers who want to build a real device;
  • people who want to modify the circuit instead of only buying a ready-made pedal;
  • anyone interested in distortion, clipping, filtering, and analog sound shaping.
It is not intended to be a final “perfect boutique pedal” in the first revision.
It is a starting point: a pilot PCB that can be tested, improved, remixed, and turned into a more complete effect pedal.
Project Status
This is a pilot hardware project.
The current goal is to create and validate the first working version of the Distortion PCB. The design is intentionally flexible and uses connectors for the parts that depend on the final enclosure: potentiometers, jacks, footswitch, LED, and other external controls.
The project is alive and still evolving.
The next important improvements are:
  • validate the core distortion circuit;
  • improve output filtering;
  • test different potentiometers;
  • check noise and grounding;
  • capture oscilloscope measurements;
  • prepare audio samples;
  • document off-board wiring;
  • consider a future dual-mode version with overdrive and distortion;
  • prepare a more polished enclosure-ready revision.
This is not the final version.
It is the first strong step toward a custom, understandable, modifiable distortion pedal.
Fork it, test it, measure it, make it noisy, make it musical, and then make it better.
Project Documentation
This project includes additional documentation for firmware, flashing, relay-path debugging, and prototype bring-up.
Final Firmware & Flashing Instructions
Complete ATtiny212 firmware guide, Arduino IDE setup, megaTinyCore configuration, jtag2updi flashing steps, and final firmware behavior.
Open Final Firmware & Flashing Instructions
Relay Distortion Path Debug Analysis
Debug analysis of the relay bypass path, D2 flyback diode orientation, K2 relay contact mapping, U4 anti-pop mute, power rails, and output signal path.
Open Relay Distortion Path Debug Analysis
Firmware Starter — ATtiny212 Relay Bypass Pedal
Starter firmware documentation for the ATtiny212 relay bypass pedal, including schematic-derived pin mapping and basic relay / LED control logic.
Open Firmware Starter — ATtiny212 Relay Bypass Pedal
License
This project is released as open hardware.
Recommended first-publication license:
  • Hardware design files: MIT License, unless otherwise stated.
  • Documentation and images: MIT License, unless otherwise stated.

  • README

  • Modern Distortion Effect Pedal

  • Video

  • Project Overview

  • Key idea

  • Why I built this

  • Design philosophy

  • Main features

  • Why these components

  • Issues Found and Next Steps

  • Off-board connectors and enclosure flexibility

  • Input, output, controls, and connectors

  • Current limitations and things to improve

  • Output filtering

  • Power filtering

  • Potentiometers

  • Grounding and wiring

  • Validation

  • Testing and validation

  • Modern Pedal Distortion — custom guitar pedal sound created with Flux.ai

  • Safety and first power-up notes

  • Manufacturing notes

  • Want to remix this?

  • Dual sound version

  • Overdrive + Distortion version

  • Improved tone/filter section

  • Better mechanical version

  • Measurement-focused version

  • Who this is for

  • Project Status

  • Project Documentation

  • Final Firmware & Flashing Instructions

  • Relay Distortion Path Debug Analysis

  • Firmware Starter — ATtiny212 Relay Bypass Pedal

  • License