PiFX, The Pi-Powered Pedal Board

Since the beginnings of the Raspberry Pi, [Tibbbbz] has wanted to build a DIY guitar effects board and amp simulator. A device like this, and similar ones sold by Boss and Kemper, put a bunch of processing power inside a metal enclosure with some footswitches and a pair of quarter inch jacks for input and output. Mash some buttons and wicked toanz come out the other end. Now this is actually possible with a Pi, and it’ll sound great too.

Because this is an audio application, latency is critical. It doesn’t really matter if you have 200 milliseconds of latency when scrolling through your Facebook feed, but for real-time audio processing anything over five milliseconds is disorienting and nearly unusable. [Tibbbbz] is using a standard, off-the-shelf USB audio adapter that gets the latency down to about that level. A Raspberry Pi is never going to have latency as low as a handful of transistors in a analog effects pedal, but it’s close enough.

For the audio system, it’s all about JACK audio: a wonderful frontend for the Linux audio system. The actual pedal emulation is happening with Guitarix. For the hardware part of this build, there’s actually not that much going on here apart from a USB sound card and a touch screen display. The footswitches are the most interesting as they’re wired up as buttons in a repurposed USB keyboard controller board. This repurposing of a USB keyboard is rather interesting, because it vastly simplifies the entire build. All of this is wrapped up in a wedge-shaped walnut pedalboard that’s sturdy enough to live on the stage at least part of the time. You can check out the demos here.

This Is The Delay Pedal You Can Build Yourself

If you’re looking to make money in electronics, there’s no better market than guitar pedals and modular synths. The margins are high, and all the consumers are otakus who will spend outrageous amounts of money chasing the next big thing. The products are just one step above audiophile wank with zero oxygen cables, and if your opamp sounds ‘more transparent’, you’re going to make a fortune, never mind how something can sound more transparent, whatever that is to begin with.

If you want to do something really cool, build a delay, because everyone needs another delay. If you want to build the latest in delay technology, just grab a PT2399 chip. That’s what ElectroSmash did with their Open Source Time Manipulator delay. Everything’s right there, all the parts of the circuits are described, and you too can become an effects pedal engineer.

This pedal is based on the PT2399 chip from Princeton Technology, a digital delay chip that can be used with something that sounds like an old-school bucket brigade chip or something resembling a tape echo. As a digital chip, you’ve also got the clean, clear sounds of a digital delay, with just a few tweaks of the circuit. We’ve taken a look at the PT2399 before, but surprisingly not many people are sharing their secrets.

The circuit for the ElectroSmash Time Manipulator is built around the ATMega328, the same chip in the Arduino Uno, with two PT2399s that can be configured to operate in serial or parallel for everything from a slapback echo to a 600ms digital delay. If you set everything right, you can get choruses, reverbs, or some psychobilly flange-ish sounds.

The entire circuit is open, with a board designed in KiCad, the code is right there written in C, and the only hard-to-replicate tech is the PT2399 chip itself, which can be had from the usual vendors for less than a dollar a piece. It’s a great pedal, and be sure to check out the video below.

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Simple Hack Completely Changes The Sound Of This Piano

We’re partial to musical instrument hacks around here, mainly because we find instruments to be fascinating machines. Few are more complex than the piano, and, as it turns out, few are quite so hackable. Still, we have to admit that this ragtime piano hack took us by surprise.

We always thought that the rich variety of tones that can be coaxed from a piano, from the tinny sound of an Old West saloon piano to the rich tones of a concert grand, were due mainly to the construction of the instrument and the way it’s played. Not so, apparently, as [Measured Workshop] demonstrated by installing a “mandolin rail” in a small upright piano. The instrument had seen better days, so step one was disassembly and cleaning. A wooden rail spanning the entire width of the string board was added, with a curtain of fabric draping down to the level of the hammers. The curtain was cut into a fringe in the same spacing as the hammers – marking the hammer locations with cornstarch was a nice trick – and metal clips were crimped to each fringe. The completed mandolin rail can be raised and lowered using a new foot pedal, completely changing the tone as the hammers hit the strings with the metal clips rather than their soft felt heads. It makes the piano sound a little like a harpsichord, or the aforementioned saloon instrument, and at the touch of a foot, it’s back to its original tone.

Most of the piano hacks we offer tend toward the electronic variety, so it’s nice to see a purely mechanical piano hack for a change. And if the hacked piano doesn’t work out as an instrument, you can always turn it into a workbench.

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Stomping On Microcontrollers: Arduino Mega Guitar Effects Pedal

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.

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MIDI Guitar Pedals

Ever since Jimi Hendrix brought guitar distortion to the forefront of rock and roll, pedals to control the distortion have been a standard piece of equipment for almost every guitarist. Now, there are individual analog pedals for each effect or even digital pedals that have banks of effects programmed in. Distortion is just one of many effects, and if you’ve built your own set of pedals for each of these, you might end up with something like [Brian]: a modular guitar pedal rack.

ae0fmjxTaking inspiration from modular synthesizers, [Brian] built a rack out of wood to house the pedal modules. The rack uses 16U rack rails as a standard, with 3U Eurorack brackets. It looks like there’s space for 16 custom-built effects pedals to fit into the rack, and [Brian] can switch them out at will with a foot switch. Everything is tied together with MIDI and is programmed in Helix. The end result looks very polished, and helped [Brian] eliminate his rat’s nest of cables that was lying around before he built his effects rack.

MIDI is an extremely useful protocol for musicians and, despite being around since the ’80s, doesn’t show any signs of slowing down. If you want to get into it yourself, there are all kinds of ways that you can explore the studio space, even if you play an instrument that doesn’t typically use MIDI.

Busted Wah Pedal Becomes New Synth Tool

Sometimes we get lucky and find a part we need for a project in our parts drawer. [Scissorfeind] got even luckier and found a part for his project lying around in the street. It was a Crybaby Wah pedal, a classic effects pedal typically used for a guitar. Since it was somewhat damaged, [Scissorfeind] got to work creating a control voltage (CV) and volume circuit for his Korg synthesizer.

For those who aren’t synthesizer aficionados, CV is a method of controlling the pitch of a tone. A higher voltage creates a higher tone and vice-versa. The wah pedal has a rocker on it that allows one’s foot to control the effect, but this particular one has been modified for CV instead of the wah-wah sound these pedals normally make. [Scissorfeind] built in a switch that will allow it to control volume as well, which makes this pedal quite unique in the effects world.

[Scissorfeind] built the custom circuit out of other parts he had lying around (presumably not in the street) and put the entire thing together on perfboard, then fit it all back together in the pedal. Now he has a great control voltage pedal for the vintage Korg synthesizer he recently restored! [Scissorfeind] knows his way around a synth, but if you’re looking to get started on a synthesizer project we have a great tutorial for you!

A Pedal Powered Cinema

When the apocalypse hits and your power goes out, how are you going to keep yourself entertained? If you are lucky enough to be friends with [stopsendingmejunk], you can just hop on his pedal powered cinema and watch whatever movies you have stored on digital media.

This unit is built around an ordinary bicycle. A friction drive is used to generate the electricity via pedal power. In order to accomplish this, a custom steel stand was fabricated together in order to lift the rear wheel off the ground. A 24V 200W motor is used as the generator. [stopsendingmejunk] manufactured a custom spindle for the motor shaft. The spindle is made from a skateboard wheel. The motor is mounted in such a way that it can be lowered to rub the skateboard wheel against the bicycle wheel. This way when the rear bicycle wheel spins, it also rotates the motor. The motor can be lifted out of the way when cruising around if desired.

The power generated from the motor first runs through a regulator. This takes the variable voltage from the generator and smooths it out to a nice even power signal. This regulated power then charges two Goal Zero Sherpa 100 lithium batteries. The batteries allow for a buffer to allow the movie to continue playing while changing riders. The batteries then power the Optomo 750 projector as well as a set of speakers.