This DIY Guitar Pedal Is Ready for the Next Stage

Guitarists have long been able to use effect pedals to modify the sounds emanating from their amplifiers, which traditionally use a variety of discreet electronics to create interesting sounds. They can typically be adjusted up to a point, or chained together with other devices.

With the advent of small and inexpensive computing hardware, it's now possible to make a programmable effects pedal that can change how it works via software. Although still a prototype, Steven Hazel built a prototype guitar pedal based on the Adafruit Feather M4 Express. A Teensy Audio Adapter board with an SGTL5000 chip acts as its audio codec.

The Feather and Audio Adapter were first tested on a breadboard, then transferred to a pedal PCB, with the addition of quarter-inch jacks and a foot switch. The PCB is based on an obsolete SparkFun Proto Pedal design, which was modified in KiCad for use in this setup.

To finish the build, Hazel needed to program it with a guitar effect. While example code/effects worked, he instead programmed a tremolo effect from scratch, which uses an LFO to turn the volume up and down. More info on programming effects can be found here, and code for this particular sound is up on GitHub. The PCB design appears to be unpublished as of this writing, but if you ask nicely they may actually send you one!

This is the first PCB Hazel made, and he found getting a board back to hold in your hands to be a magical experience. I’d certainly agree with this assessment, though plan for the first one to be a learning process one way or another! If you’re more experienced, don't forget to savor the joy of your design, whether it's PCB number 1 or 100.