Multi fx Stomp Box

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

Public Chat
Similar projects worth following
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 create a single pedal that I can use to do all of the above.

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 × Wah Pedal To remove internal circuitry and replace with the Pro Micro
  • 1 × AudioInjector Soundcard ADC / DAC conversion. Replaces the USB interface required previously
  • 5 × Footswitches
  • 1 × bundle of wires for connecting it all together

View all 8 components

  • Enclosure Update

    Craig Hissett10/10/2019 at 20:14 0 comments

    Case assembled, sockets in place.

    Next step is to mount the 50w power supply, add the Pi on standoffs and then wire this little beauty up.

  • Another piece of the acrylic puzzle

    Craig Hissett10/03/2019 at 21:36 0 comments

    The top panel has now been machined 😎

  • Enclosure

    Craig Hissett06/23/2019 at 06:49 0 comments

  • Progress update

    Craig Hissett06/10/2019 at 16:31 0 comments

    Apologies for the lack of updates on this bad boy - progress is still slowly ticking away in the background!

    I'm currently fixing some issues in the software at present; upgrading everything to allow the use of the AudioInjector card has broken my WiFi, unfortunately. I've slowly getting to the the bottom of it, but it has been a time consuming and frustrating affair.

    I have also been doing some work on the Wah/Expression Pedal input; rather than sticking an arduino in and plugging it in I am tempted to experiment with an ESP8266 to send data wirelessly.

    I already have a python script translating GPIO pin button presses into MIDI, so adding some further code in there to translate incoming data is entirely plausible.

  • Audioinjector working

    Craig Hissett03/31/2019 at 00:45 0 comments

    My test build is almost ready to rock!

    I've updated the software to use the new audio interface, and it works brilliantly. There's scope to really improve then latency and overall performance once finished.

    All i need to do is still out back panel holes, wire up my ins and outs, then test it.

    If it all fits nicely I'll be building a proper case for it :)

  • Building | Test casing

    Craig Hissett03/20/2019 at 01:02 0 comments

    Putting together a test enclosure to see how my estimates work out. It Is looking though a 5cm height at the back and 3cm at the front will in fact leave enough space inside for the Pi and hat. I may add 1cm to each height for comfort.

    Just need to rewire my switches, adjust my code for the new audio interface and it should be ready to test. Once testing is complete it'll be rehomed in a much better case.

  • New Arrival | Audioinjector HAT

    Craig Hissett03/19/2019 at 12:09 0 comments

    Ah, isn't it beautiful?!

    Now, to crack on with assembling the test case.

  • Enclosure v1

    Craig Hissett03/11/2019 at 01:03 0 comments

    Here is the first iteration of my case:

    Tomorrow I will get this cut out at work and stick together; I have added a cut out for the Pi ports on the back, but will need to drill out the sockets for the xlr/Jack inputs x2 and the jack sockets  out x2 and a headphone jack out.

    The analog expander chips I have ordered won't work with the Pi (I need an analog pin to expand of course) so a new chop will need to be ordered.

    Not to worry though, as my expander chips will be getting put to use with an Arduino Pro Micro to make a simple electronic drum brain.

  • Finally, a build update

    Craig Hissett03/01/2019 at 01:27 0 comments

    Sorry for the long delay between updates folks.

    Build update :- I am currently working on building a little enclosure to house my Pi and the 5 switches. I have a few analog expander chips on the way, which I will use to add a potentiometer to my inputs to simulate an expression pedal.

    Today i have also ordered an audioinjector soundcard for my Pi:

    I really wanted to make my pedal all inclusive, and plugging in a USB interface to handle audio, well, it sucked.

    This soundcard will go onto my Pi, connects via SPI (leaving all my gpio pins used fornbutton handling completely free for that job) and is already supported in the Linux kernel so it shouldn't take a while lot of work to have it working with JACK.

    I'm feeling good about this build ; once my parts arrive Ibshould be able to finally build it, and for once it'll actually match what I had in my head when I first set out to build it.

  • It's alive!

    Craig Hissett02/18/2019 at 01:56 0 comments

    It's 1:55am, but I finally have some good progress to report!

    I've managed to get a few buttons connected directly to the Pi to pass MIDI instructions to the MODEP software.

    This is handled by a Python script on startup, opening a virtual MIDI port for the script to send commands.

    It works great with the software, and it's really easy to set up a control to be handled by the physical buttons.

    I've also tweaked the Jack server running on the device, reducing the issues ideas having with sound quality dramatically.

    Next step is to add a few more buttons and an encoder or two into the script, and prepare for an analog expander chip that's on its way. This will read potentiometer values from expression pedals.

    I also want to build a nice case to put this in too :)


View all 24 project logs

Enjoy this project?



Paul Burford wrote 09/08/2019 at 16:23 point

Hi Craig! After recently mentioning my guitar Arduino controlled valve amp, thought I'd send you a link to it. I haven't uploaded all the info but it's getting there.

Any news on the effects unit?

  Are you sure? yes | no

tom wrote 06/17/2019 at 22:31 point

Inspiring project.  I'd like to build one myself.  Can you tell us why you went with the AudioInjector board vs the PiSound?  

  Are you sure? yes | no

Craig Hissett wrote 06/18/2019 at 16:29 point

Thanks Tom.

The main reason for going for the AudioInjector was intrigue; I was fascinated to see what the interface could do for such a low price. The PiSound boards are great, but are quite expensive and without any real funds to throw at this I had to go cheap :)

In addition to cost I always had a vision of wanting to piece together my own pedal layout, using multiple buttons, encoder, screens etc so going with a generic card is handy.

  Are you sure? yes | no

tom wrote 06/18/2019 at 16:34 point

Price I can definitely understand.  Are you saying that Audioinjector allows you to use the GPIO pins where the PiSound doesn't?  Is there a difference in latency between the 2 audio cards?

  Are you sure? yes | no

Craig Hissett wrote 06/18/2019 at 17:31 point

The Audioinjector has all pins passed through, so it makes it easy to expand. 

As far as latency is concerned I haven't yet put it through it's paces properly but the Audioinjector forums look very promising with the performance.

It should handle the processing for the guitar software perfectly :)

  Are you sure? yes | no

tom wrote 06/18/2019 at 17:58 point

Thanks for the info.  Please let us know how it goes!  

  Are you sure? yes | no

tom wrote 06/18/2019 at 19:12 point

Sounds like you are trying to avoid adding MIDI to this project so you can roll your own buttons/pots w/ the GPIO?  Keeps it simple, though then you have to handle sampling the buttons/pots in RPI side of things?

  Are you sure? yes | no

Craig Hissett wrote 06/18/2019 at 19:21 point

Yes and no ;)

While there's no actual ports for it yet, MIDI is still an important part of this build; my python script that reads the buttons created a virtual MIDI port and sends MIDI commands when the buttons are pressed.

This will allow me to add more devices (via i2c, serial etc) and easily integrate them with a slight adjustment of the python script.

I'm also looking at a wireless expression pedal for this, having an esp8266 and a 9v battery read the potentiometer of a way pedal and use the python script to interpret that too.

  Are you sure? yes | no

castvee8 wrote 04/04/2019 at 15:30 point

Nice project Craig! got one going myself again this year. hope you do well.

  Are you sure? yes | no

Craig Hissett wrote 04/04/2019 at 19:59 point

Thanks mate! The project is shaping up nicely; just a few cables to solder, holes to cut, then a new case to be built :)

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates