A collection of schematic designs and modified versions of existing circuits for audio applications, such as guitar pedals, preamplifiers, power amplifiers, and other audio electronics.
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Guitar pedals
- Distortion/Fuzz
- Utility
- Guitar preamplifiers
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Power amplifiers
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Utility
The schematics are made using KiCad EDA, free & open-source software.
An example how to open a project from a command-line:
kicad wenzels-headphones-stereo-amp/headphones-amp-dual-supply.kicad_proThen you can find the schematic files in the file tree on the left.
There is a Nix configuration for the project that supplies dependencies (KiCad in particular). So you can just run from the project root:
nix-shell
kicadIt will use your system nixpkgs pin.
If you want to make sure you use the same KiCad version as me then use
pinned-nixpkgs boolean attribute:
nix-shell --arg pinned-nixpkgs true
kicadIt will read the pin from nix/nixpkgs.pin.nix.
N.B. KiCad, together with it’s components library, is big and heavy, before you enter the nix-shell for the first time, before KiCad is cached on your local machine it will take quite a bit of time and disk space to get it ready.
There are other dependencies supplied too, such as ImageMagick for example for converting PDF schematic renders to PNG format.
There are some useful scripts that help with working with the project:
- Convert schematic PDF to PNG format: dev-scripts/render-kicad-schematic-pdf-to-png.sh
All hardware design files in this repository — including KiCad project
files (.kicad_pro, .kicad_sch, .kicad_pcb), symbols, footprints, 3D
models, and any PDF & PNG renders of the schematics or boards — are
licensed under the:
CERN Open Hardware Licence Version 2 – Strongly Reciprocal (CERN-OHL-S-2.0) SPDX: CERN-OHL-S-2.0
Unless a subdirectory explicitly specifies another licence, all KiCad projects under this repository fall under this licence.
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You are free to use, study, modify, make, and sell hardware based on these designs.
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If you modify or extend the design, or create derivative works, you must:
- Share your modified source files (schematics, layouts, etc.) under the same licence.
- Preserve attribution and licence notices.
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If you manufacture or distribute a physical product derived from these designs, you must also make the corresponding design sources available under the same licence.
In short:
CERN-OHL-S for hardware is what the GNU GPL is for software — it ensures that derivatives and improvements remain open-source and freely available to others.
For the full licence text, see: https://spdx.org/licenses/CERN-OHL-S-2.0.html
Non-hardware support files — such as build scripts, shell utilities, or Nix configuration files — are licensed separately under the permissive MIT License, unless otherwise noted within their directories or file headers.
See individual files or subdirectories for their specific licence headers.
| Type of file / directory | Default licence | Notes |
|---|---|---|
.kicad_pro, .kicad_sch, .kicad_pcb, .kicad_mod, .kicad_sym |
CERN-OHL-S-2.0 | Core open-hardware design sources |
.step, .wrl, .3mf, .stl |
CERN-OHL-S-2.0 | 3D models used in hardware design |
.pdf, .png (renders of schematics or boards) |
CERN-OHL-S-2.0 | Visual renderings of open-hardware designs |
flake.nix, .nix, .sh (utility scripts) |
MIT | Supporting software/configuration only |
Any other folder with its own LICENSE |
As stated there | Overrides the repository default |
This repository collects multiple hardware projects in subdirectories.
Unless explicitly stated otherwise (e.g. with a different LICENSE file in a
specific project folder), all hardware projects are licensed under
CERN-OHL-S-2.0.
Software or configuration files accompanying those projects use the MIT License.
SPDX identifiers for clarity:
- Hardware source files:
SPDX-License-Identifier: CERN-OHL-S-2.0 - Scripts/config files:
SPDX-License-Identifier: MIT