Normally guitar pedals take in a signal from your instrument, then some modification to an amplifier. ElectroSmash’s open source device, however, looks like a guitar pedal, connects to a guitar and amp like a guitar pedal, but actually leaves the signal unmodified. Instead, it displays a variety of info about what you’re playing on its 16 x 16 LED matrix.

The Arduino Audio Meter uses an Uno for control and analysis, and acts as a VU meter by reading the incoming audio and creating LED animations. It also features a tuner function, visual metronome, frequency detector, and a simple lamp, which could all certainly be useful when playing. 

User input (besides the1/4-inch audio jack) is via a potentiometer and encoder, and it even has a few games available for it if you need to blow off some steam between sets! Build kits are available here if you’d like to make your own.

Effects pedals: for some an object of overwhelming addiction, but for many, an opportunity to hack. Anyone who plays guitar (or buys presents for someone who does) knows of the infinite choice of pedals available. There are so many pedals because nailing the tone you hear in your head is an addictive quest, an itch that must be scratched. Rising to meet this challenge are a generation of programmable pedals that can tweak effects in clever ways.

With this in mind, [ElectroSmash] are back at it with another open source offering: the pedalSHIELD MEGA. Aimed at musicians and hackers who want to learn more about audio, DSP and programming, this is an open-hardware/open-software shield for the Arduino MEGA which transforms it into an effects pedal.

The hardware consists of an analog input stage which amplifies and filters the incoming signal before passing it to the Arduino, as well as an output stage which does the DAC-ing from the Arduino’s PWM outputs, and some more filtering/amplifying. Two 8-bit PWM outputs are used simultaneously to make pseudo 16-bit resolution — a technique you can read more about in their handy forum guide.

The list of effects currently implemented covers all the basics you’d expect, and provides a good starting point for writing custom effects. Perhaps a library for some of the commonly used config/operations would be useful? Naturally, there are some computational constraints when using an Arduino for DSP, though it’s up to you whether this is a frustrating fact, or an opportunity to write some nicely optimised code.

[ElectroSmash] don’t just do pedals either: here’s their open source guitar amp.