Modular Multi fx Stomp Box

I am looking to build a modular 'pedalboard in a box'.
It's so crazy it just might work...

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Disclaimer - at present this is nothing more than a silly idea that I would like to delve into and research.
I am a trombone & guitar player, and have recently been messing around with guitar effects while playing in the studio, and would love to build a custom device that can act as an effects box with some real flexibility.
The setup I have recently used has been a bit bulky; with most guitar pedals being line level I have been using an 8 channel mixer to plug my mic in, then taking the aux out of that channel through the pedals and back into another channel on the mixer. This was handy as it gave me a wet and dry signal out of the setup. The pedals I was running through was a Yamaha Magicstomp (a great programmable multi fx unit) and a line6 floorpod (great for amp sims and other additional delays, plus the volume pedal was fantastic for controlling the level of wet signal).

I'd like to use a handful of Pis/Arduinos to create a modular box for all occasions :)

After a few rehashes, the plan currently is:

An all-in-one multi fx pedal based on the Raspberry Pi.

A usb interface will handle the sound input and output, and an Arduino based footswitch will control the parameters of the software running on the Pi.

Used to make first basic images of test board

ms-publisher - 1.85 MB - 11/03/2018 at 01:52


  • 1 × Raspberry Pi To process audio
  • 1 × Raspberry Pi To process audio
  • 1 × USB Audio Interfscr ADC / DAC conversion
  • 1 × USB Audio Interfscr ADC / DAC conversion
  • 1 × Arduino Pro Micro Brains of footswitch

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  • Hmmm... Noisy

    Craig Hissett12/04/2018 at 21:17 0 comments

    I got to give my board a go today  and had mixed results.

    The board worked, however there appeared to be a lot of digital noise in my headphones.

    I'm going to do some trouble shooting and see if I can isolate the problem, as it could be an issue with my interface.

    The footswitch is an old project that I'm hoping to use as a stopgap while testing my board. Hopefully it'll be working over the next few days too.

  • A Case for the pedal

    Craig Hissett11/24/2018 at 01:37 0 comments

    I have an old Stagg case that I used to keep a some guitar stuff in.

    Its ideal for this build; the hinges separate, meaning I can build my project into the lid and just remove the rest of the case for use.

    This pic shows the Pi and interface in there, with an Arduino Pro Micro breadboard set up to test a 5 button, 2 potentiometer midi interface.

    Once I've got a script that will work with the software I'll build a footswitch into the case.

    The Pi and Arduino will be inside the footswitch, and the interface with be countersunk into the top of the angled switch. The space on the right of the picture will be where I build an expression pedal.

  • Software Success!

    Craig Hissett11/23/2018 at 00:53 0 comments

    Tonight I managed to get my Pi software configured and loading with my audio interface. Good times!

    Tomorrow at a more appropriate hour I shall put together a sample effects chain and test out latency and adjust following testing.

    After that - footswitch building and mounting in its case.

    Until then, here's the interface on my phone:)

  • MIDI Footswitch

    Craig Hissett11/21/2018 at 00:35 0 comments

    I've found the perfect style of MIDI USB footswitch for my project:

    One of these (albeit on a slightly smaller scale) will pass MIDI control signals to the Pi to control the switching on/off of pedals in the software.

    I could also like to mod this design to incorporate two potentiometers for Expression pedal input.

  • Prototyping

    Craig Hissett11/19/2018 at 21:04 0 comments

    over the next few nights i will start putting this all together in prototype form.

    I have modep image on a card, and just need to iron out some config issues to be up and running.

    For the footswitch testing I gave attached a little dual analog stick board to simulate the footswitch. The board has potentiometers to simulate an expression pedal input, and clickable buttons in the centre of the sticks to test out the footswitches in my code.

    I've also dug out an old Stagg case I used to carry a few pedals in, and this will form the base of my board.

    Once the Pi, interface and footswitch are in all that's left to do is build two expression pedals to operate pots for the Pi and enclose all the wiring for a neat finish.

  • Update | Looking good!

    Craig Hissett11/17/2018 at 23:42 0 comments

    Today I have found some great software to run on my project: Modep.

    Modep is an emulated version of some software running on a new device called a Mod Duo, which is a Linux based Stompbox with a web interface for selecting the patches and assigning controls.

    Modep will run on a Raspberry Pi and can accept controls from USB MIDI, meaning I can build the Arduino controller board part of the pedalboard using a Pro Micro (Atmega32U4).

    This will allow me a number of buttons (say 5 effect on/off buttons, 2 more for expressiin pedals on/off, some digital rotary encoders for adjusting parameters and some analogue potentiometers to mimic expression pedals).

    If the pins are spare it may be even possible to add an i2c display for feeding back midi messages.

    The Alesis io2 has two midi ports on the back of it so it is perfect for expansion in the future.

    I'm really excited to get this built this week.  I am also looking to implement some of this softeare/hardware setup into my DigiBone project too.

  • Digging

    Craig Hissett11/14/2018 at 00:02 0 comments

    I managed to find an old footswitch I built many moons ago.

    This grey monstrosity,  pictured next to a Line 6 FBV footswitch, will be ideal to modify into my input device.

    I might even squeeze the Tinkerboard inside, plus it could be modified to have a slot for the interface to fit into.

  • Collecting Parts

    Craig Hissett11/08/2018 at 00:26 0 comments

    Tinkerboard and the Alesis io2:

    I built a footswitch a few years ago to allow triggering keyboard shortcuts on my PC while in the studio recording; I plan to dig it out and remove the switches and use them to rebuild an interface for this little beauty.

    I would like to knock up two customs length USB cables in order to keep it all neat.

  • Software | Pure Data?

    Craig Hissett11/04/2018 at 07:27 0 comments

    I've been looking for some options for software to run on the Tinkerboard.

    Pure Data has cropped up in a few old examples and I think it is worth some investigation.

    This example uses PD on a Raspberry Pi, controlled via TouchOSC app on a phone:

    And this one is a project that uses PD with an Arduino (running Firmata) as an input reading Stompbox switches and a DIY expression pedal:

    I would love to take elements from both of these to come up with a setup that can operate like the second link, with a TouchOSC interface for more complex parameter editing.

  • Testing Setup

    Craig Hissett11/03/2018 at 01:45 0 comments

    Over the next week I'm going to aim to assemble a test board to start playing around with using a linux SBC to process audio, and using an Arduino to display updates on a display and pass input parameters from stompbox switches.

    While in future iterations I'd like to incorporate the XLR and jack inputs and outputs this testing setup will use an external interface mounted to the test board.

    The Alesis io2 interface is perfect for this setup; it's plug and play, has XLR inputs and line inputs, has insert points for adding more effects if necessary and a headphone out. The added bonus is I have one spare :)

    For the SBC I have opted for an Asus Tinkerboard. It's more powerful specs will help keep latency to a minimum.

    I will look for various examples of software to try out; I'm looking for something I can run headless and preferably use Python to manipulate parameters (this will make using the arduino a lot easier).

    Another nice feature would be to connect to the Tinker board to use a web interface for a more detailed user interface.

    While a test rig I'd love to make this device look the part. I'd like to mount everything to a base plate and place a cover over the Tinkerboard and arduino, make cutouts for the switches, the lcd screen and also a small opening for the interface USB cable to pass through. Adding some panelmount sockets for ethernet and the two spare USB ports would be great for expandability and connecting for programming and updating.

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