Ever wondered how to approach making your own digital guitar effects pedal? [Steven Hazel] and a friend have done exactly that, using an Adafruit Feather M4 Express board and a Teensy Audio Adapter board together to create a DIY programmable digital unit that looks ready to drop into an enclosure and get put right to work in the studio or on the stage.
[Steven] also made a custom PCB to mount everything, including all the right connectors, but the device can be up and running with not much more than the two main parts and a breadboard.
On the inside, the Adafruit Feather M4 Express board works with the audio board over I2S, a standard for sending serial digital audio between chips. Working with the audio itself is done with the Teensy Audio Library, providing a fantastic array of easy-to-use functions for processing and manipulating digital audio streams.
Looking for a hands-free way to page through sheet music on an iPad, [The_Larch] came up with this simple Bluetooth input device based on the ESP32. The microcontroller just needed to have two switches wired into the GPIO pins, in this case the same heavy-duty plungers you’d find on a guitar pedal, and a USB bulkhead pass-through to provide power. Thanks to the excellent ESP32-BLE-Keyboard library, it only took a few lines of code to fire off the appropriate key strokes when the left or right button was pressed.
While undeniably a simple project from an electronics standpoint, the wooden enclosure [The_Larch] built is an interesting change of pace from the 3D printed fare we normally see around these parts. It started life as strips of oak reclaimed from an old kitchen table, which were laminated together to make a solid block. A large spade bit was then used to bore into the block to make a void for the electronics, and a second flat piece of oak was fashioned into a front panel.
It’s a common problem: you’re at a party, there’s a guitar, and your plan to impress everyone with your Wonderwall playing skills is thwarted by the way too loud overall noise level. Well, [Muiota betarho] won’t have that issue ever again, and is going to steal the show anywhere he goes from now on with his Crazy Guitar Rig 2.0, an acoustic guitar turned electric — and so much more — that he shows off in three-part video series on his YouTube channel. For the impatient, here’s video 1, video 2, and video 3, but you’ll also find them embedded after the break.
To start off the series, [Muiota betarho] adds an electric guitar pickup, a set of speakers, and an amplifier board along with a battery pack into the body of a cheap acoustic guitar. He then dismantles a Zoom MS-50G multi-effect pedal and re-assembles it back into the guitar itself with a 3D-printed cover. Combining a guitar, effect pedal, amp and speaker into one standalone instrument would make this already an awesome project as it is, but this is only the beginning.
So, time to add a Raspberry Pi running SunVox next, and throw in a touch screen to control it on the fly. SunVox itself is a free, but unfortunately not open source, cross-platform synthesizer and tracker that [Muiota betarho] uses to add drum tracks and some extra instruments and effects. He takes it even further in the final part when he hooks SunVox up to the Raspberry Pi’s GPIO pins. This allows him to automate things like switching effects on the Zoom pedal, but also provides I/O connection for external devices like a foot switch, or an entire light show to accompany his playing.
With little more than a gutted record player, a light bulb, and the legendary 555 timer IC, [Jacob Ellzey] has constructed this very slick optical tremolo effect for his guitar. By modulating the volume of the input signal, the device creates the wavering effect demonstrated in the video after the break.
The key is a vinyl record with large tabs cut out of it. As the record spins, these voids alternately block and unblock a small incandescent bulb. A common GL5537 photoresistor, mounted on the arm that originally held the player’s needle, picks up the varying light levels and passes that on to the electronics underneath the deck. An important note here is that different spacing and sizing of the cutouts will change the sound produced by the effect. [Jacob] has already produced a few different designs and plans on experimenting with more now that the electronics are completed.
Under the hood there’s a voltage divider and low gain amplifier connected to the photoresistor, and also a 555 timer circuit that’s driving the incandescent bulb. Once he was done fiddling with them, the circuit was moved to a neat little protoboard. A pair of potentiometers mounted through the side of the record player allow for adjusting the depth of the effect itself, as well as the output volume. Naturally, there’s also an external foot pedal that allows keying the effect on and off without taking your hands from the guitar.
As is usually the case, everything was going well on this project until the final moments, when [Jacob] found that the circuit and bulb were both browning out when powered from the same transformer. As a quick fix, he gutted a Keurig and used its transformer to drive the light bulb by itself. With independent power supplies, he was ready to rock.
Over the summer [ElectroSmash] put the finishing touches on the Arduino Audio Meter, a shield for the Arduino Uno that visualizes various aspects of an incoming audio signal on a set of four 8×8 LED dot matrices. Obsentisibly it’s for use on a guitar pedalboard, but thanks to the incredible documentation and collection of example code provided by the team, the project promises to be an excellent platform for all sorts of audio experimentation.
Incoming audio is amplified with an MCP6002 and fed into the Uno’s Analog to Digital Converter, where it’s processed via whatever Sketch the user has uploaded. User input is provided by a digital encoder with push-button. A set of four MAX7219 chips control the entire 256-pixel matrix with just three pins on the Arduino. The resolution of the display allows the Arduino Audio Meter to show more than just a simple VU meter, it can even do text and basic graphics.
[ElectroSmash] provides various Sketches for use with the Arduino Audio Meter that provide the expected repertoire of audio visualizations, but they also provide a number of interesting Sketches to expand the capabilities of the device in unexpected ways. Some of them could be useful for a stage musician, such a tool to tune your guitar, whereas others are fun uses of the hardware such as a game of “Snake”.
With the entire project released as open source, users are free to run wild with the Arduino Audio Meter. Writing your own custom software is an obvious first step to making the project your own, but adding additional hardware features and functions certainly aren’t out of the question either.
Our very own [Lewin Day] once walked us through the effort involved in building boutique guitar pedals, and while the Audio Audio Meter’s capabilities are somewhat limited as it doesn’t have the ability to change the audio going through it, we’re still interested in seeing what the community will come up with once they have an easy way to bring their ideas to life.
From building your own analog effects pedal to processing audio through micro controllers, a lot of musicians love building their own boxes of sound modification. In his entry for the 2019 Hackaday Prize, [Craig Hissett] has a project to build an all-in-one multi-effects stomp box.
At the center of the box is a Raspberry Pi with an AudioInjector stereo sound card. The card takes care of stereo in and out, and passing the signal to the Pi. The software is Modep, an open source audio processor that allows the setup of a chain of digital effects plugins to be run on the Pi. After finding some foot switches, [Craig] connected them to an Arduino Pro Micro which he set up as a MIDI device that sends MIDI messages to the Modep software running on the Pi.
There are still a few steps to go, but [Craig] has the basic layout covered. Next up is wiring it up and building a proper case for it, as well as working on latency. A few years ago, another multi-effects stomp box was featured in the Hackaday Prize, and last year, this multi-effects controller was featured.
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.