Click here for pi-Stomp Core
Finally, you can build your own high-definition multi-effects pedal!
pi Stomp is an open source high definition multi-effects stompbox platform. The base install contains over 350 plugins - effects, modeled amps, loopers and sound generators. It was designed for guitar and bass, but works great for processing electronic instruments as well.
It sports 24-bit, 48 to 96kHz stereo audio and a Raspberry Pi 64-bit quad core processor running at 1.4 GHz
Numerous virtual pedalboards containing up to dozen or more plugins, can be constructed via MOD, a super powerful yet easy to use drag-n-drop web user interface. Each pedalboard can be saved with multiple “presets”, each being a snapshot of all the parameters for a given sound.
Once your pedalboards are saved, only the pi Stomp is needed on-stage or in the studio.
An LCD shows an overview of the current pedalboard, navigation via rotary encoder.
When it comes to amp modeling and effect processing, we’re in a golden age for guitarists. The choices for gear are almost endless. Why do we need another?
Well, almost all of the available solutions are based on proprietary platforms. pi Stomp is open source software running on hardware that You built.
Being a more open and general purpose platform, you can hack or extend it by:
It certainly is more hackable and upgrade-able! Performance wise, it's very close in many regards, and even has some unique features. But in general, if you're not the DIY type, or if you want a pro quality product, please buy one those. Each was designed by a large team, in a well funded company, and assembled in a production factory.
pi Stomp is a hobbyist project For hobbyists. If you’ve always wanted to build your own multi-effects unit, here’s your chance. I put my blood sweat and tears into it, so you can have the same enjoyment I have when I plug in and make awesome sounds thru something that I built. If you’ve ever built your own effect or amp, you know what I mean. Now imagine an entire do-anything pedalboard that conforms to your crazy musical ideas!
The flip-side is that you will need to invest some time and effort. Although the wiring is similar or even simpler than many stomp boxes, the circuit board assembly is rather advanced. Please see Building pi Stomp before purchasing parts.
|pi-Stomp Core||pi Stomp v1 (superseded by pi-Stomp Core)||MOD Duo||HX Stomp||Headrush Gigaboard|
|Audio||24-bit 48kHz or 96kHz||24-bit 48kHz or 96kHz||24-bit 48kHz||24-bit 96kHz||24-bit 96kHz|
|Number of Plugins (FX, Models, etc.)||358+ (user upgrade-able)||358+ (user upgrade-able)||330+ (user upgrade-able)||200 (not upgrade-able)||107 (not upgrade-able)|
|Simultaneous Plugins||Typ 12+ (depends on CPU demand)||Typ 12+ (depends on CPU demand)||Typ 12+ (depends on CPU demand)||6||12?|
|Plugin Routing||Completely flexible||Completely flexible||Completely flexible||Serial or two parallel||Serial or two parallel|
|Plugin types||Effects, Models, Generators, Loopers||Effects, Models, Generators, Loopers||Effects, Models, Generators, Loopers||Effects, Models, Looper||Effects, Models, Looper|
|DIN (5-pin) MIDI||Optional In and/or Out||In||In & Out||In & Out/Thru||In & Out/Thru|
|USB MIDI||In & Out||In & Out||In & Out||None||None|
|Expression Pedal Input||Optional (up to 8 Analog controls)||Yes||No||Yes||Yes|
|Footswitches||Optional (up to 13)||3 (user assignable)||2 (user assignable)||3 (multiple modes)||4 (multiple modes)|
|True Bypass||Yes for Channel 1, Chan 2 always on||Yes (latching relays - save state when powered off)||Yes (mechanical relays)||Yes (mechanical relays)||Apparently Not|
|Audio Ins/Outs||2 in / 2 out (independent or stereo)||2 in / 2 out (independent or stereo)||2 in / 2 out (independent or stereo)||2 in / 2 out (stereo)||1 in / 2 out (stereo)|
|LCD||Color!||Monochromatic||2x Monochromatic||Color||Color / Touch|
|Can use as a USB audio interface||Not currently (OTG required)||Not currently (OTG required)||Yes||Yes||Yes|
|Wireless Connectivity||WiFi & Bluetooth||WiFi & Bluetooth||WiFi & Bluetooth||None||None|
|Software/Firmware||Open Source/Hackable/Upgrade-able||Open Source/Hackable/Upgrade-able||Open Source/Upgrade-able||Proprietary/Upgrade-able||Proprietary/Upgrade-able|
|Hardware||Very Hackable/Upgrade-able||Hackable/Upgrade-able||Proprietary/Expandable via port||Fixed Proprietary||Fixed Proprietary|
|Dimensions (in)||4 x 2.7 x 1.75 (w/o enclosure), 4.7 x 3.7 x 2.0 (smallest enclosure)||7.4 x 4.7 x 2.0||7.1 x 6.3 x 2.9||7.0 x 5.0 x 2.6||13.0 x 8.9 x 2.6|
|Cost||$159 (without enclosure or other options)||$198 (depends on sources)||$550||$650||$599|
Another product by the great folks at blokas.io named “pisound” (https://blokas.io/pisound/) is similar in core functionality to pi Stomp and MOD Duo. It's not listed in the table above because it lacks features which are generally required for a stomp box form factor. Pisound has only one footswitch, no bypass, no LCD, no robust enclosure, and only stereo (TRS) jacks with rather low input impedance (100k ohm). But, for a table based mutlti-effect unit, or if keyboards are more your game, it's worth checking out.
With 24-bit 96kHz I/O and a quad core 1.4 GHz processor, pi Stomp certainly has the processing power to rival the some of the best units. A vast number of current commercial recordings have been produced within computer systems with less power than pi Stomp. And remember, rendered CD quality is 16-bit 44.1kHz.
Where commercial multi-effects are likely to excel, is in the quality of the individual effect software models. Each included effect has a whole team of sound professionals committed to creating near perfect models of popular classic and novel amplifiers, cabinets and effects. The current pi Stomp software uses the LV2 open standard for coding of plugin effect models. There are over 400 available LV2 plugins out there. However, like with any community developed open software, the quality can range from awesome to unusable.
To get a sense of what LV2 plugins are capable of, check out the example pedalboards with sound samples on the Listen page.
The LV2 standard is relatively new and the audience is smaller than the similar Windows/MacOS based audio plugin formats (VST, AU, AAX, etc.). Some of those plugins may be able to be ported to LV2. But there are also some companies/organizations/individuals creating some awesome native LV2 plugins, like guitarix and CALF. As the community grows, so will the quality. You can even be part of that! Create your own plugin (Build & deploy a LV2 plugin ), add it to your pi Stomp, share it with the world!
Although pi Stomp! can replace a full pedalboard, it can also be used quite well with your other pedals chained before, after or within the fx-loop. So your personal tone can still leverage the pedals that you love and then use pi Stomp to add effects that you don't otherwise own, wish consolidate or automate with presets, etc. One usecase, is to use it as a simple stomp box instead of a full pedalboard, providing less used effects (eg. pitch shifter, envelope follower, rotary speaker, etc.) as an alternative to cluttering your physical pedalboard with each of those.
Now we get into some geekier details. Most commercial multi-effects units are DSP based. Their processing is purpose-built to process audio in a real-time operating system (RTOS). pi Stomp! being based around Raspberry Pi and Linux, a general-purpose operating system (GPOS), is at somewhat of a disadvantage because the CPU can be busy processing tasks that a DSP doesn't have to worry itself about. The Raspbian based OS used in pi Stomp! has been optimized to eliminate or reduce many of the potential distractions that might be encountered if the Raspberry Pi was being used as a “desktop” computer, but still, buffer overruns (aka Xrun's) can be encountered when the CPU is overwhelmed and that can result in audible anomalies (eg. glitches, pops, etc.) Given the power of the Raspberry Pi 3's quad cores, Xruns are typically infrequent unless you're running a pedalboard with many plugins, greater than 8 or 10 maybe, or if quite a few of the plugins are “simulators”. The bottom line is that there's more potential for audible glitches with a GPOS based processor. A glitch here and there is usually tolerable by most recreational musicians. If you're of the more professional variety, a commercial unit might suit you better.
Digital noise is also more likely in a GPOS based system because the CPU is constantly processing requests for its many services, passing data over its various interfaces (GPIO, Wifi, etc) and radio frequency noise is just rather prevalent on development boards like Raspberry Pi. The route of digital noise into the audio path is usually via inductive coupling. Shielding and physical distance are the typical solutions applied to reduce that coupling. Experiments with shielding were done but didn't seem to reduce coupled noise by any measurable amount. Instead, I chose to keep the audio portions of the system physically sequestered to one side of the board, away from the LCD backlight and Pi as much as possible. There will be some high frequency noise noticeable when the output is sent to an amp running at high volumes. In my opinion, it's not as annoying as the noise from many gain pedals or the common 60Hz hum, but it is there and something to consider if the highest of Fi is your grail.
Actual lab test results of pi-Stomp can be found here
pi Stomp has 4 main hardware modules (circuit boards):
First, a word of caution. The required parts are a significant investment - about $195 (USD). It could easily turn into an expensive door stop if not soldered well. If you’ve not built a stomp box or similar piece of gear before, you might want to hone your skills a bit before attempting to build a pi Stomp.
Here is an excellent soldering guide: Adafruit Soldering Guide
You should be proficient with circuit board soldering and component identification. You’ll need a sharp/fine tip on your soldering iron, specifically, “pencil tip” - 1/32“ (.75mm) best but definitely no larger than 1/16” (1.5mm).
There are over 50 components and approximately 270 solder pads which need soldering. 120 of those are for the four 40-pin two-row connectors, with a distance of 0.1 inch between adjacent pads. If you can cleanly solder those without shorting pads or creating cold joints, you should be fine to build the rest.
If you're ready, you'll first need to buy the parts…
It should be possible to get all parts from just two vendors: mouser.com and treefallsound.com (or Tindie).
All required parts are listed in the: Full Bill of Materials
For your convenience, the mouser.com sourced parts are stored as a BoM on their site: Mouser pi Stomp 1.0.2 BOM
If you don't need everything in the BoM, you can still add it to your mouser.com cart, then remove the specific items you don't need.
The remaining parts (circuit board, pre-drilled enclosure, footswitches, Led's, etc.) are available from: Tree Fall Sound Store. Some parts which tend to have low stock or long lead times from mouser.com may also be available there. The same bundles are also available on Tindie
Parts were chosen to be as common and available as possible. If a specific part is not available at mouser.com or treefallsound.com, check digikey.com, newark.com for general components. adafruit.com for Pi's, LCD, etc. guitarpedalparts.com for pedal specific parts. Feel free to email email@example.com for suggestions or possible access to our stock.
If you've acquired the parts and you're ready to build, go to: Full Build Instructions
Come back here when your hardware build is complete.
Please heed these if you plan to power with anything other than the recommend power supply (listed in the BOM)
The operating system currently supported for pi-Stomp is PatchboxOS created by Blokas Labs and based on Rpi OS Lite. On top of that, you need to install the pi-stomp specific software/firmware.
PatchboxOS will either present an adhoc hotspot or it will try to connect to a router, not both. It initially will present the hotspot (named Patchbox). We'll use this so we can connect then configure wifi networking for connecting to your router which we'll need for downloading software.
patchbox wifi connect --name “SSID” --country “CC” --password “PASSWORD”
This will restart wifi on the pi (switching from hotspot to router). Your current session will end.
If your pi-Stomp connected to your home router successfully, you likely won't need to know the actual IP address and you can use
patchbox.local for the following steps. If you cannot ssh using
patchbox.local, then come back here and try some of these discovery methods. Fing, Ping or AngryIP are recommended.
If you are not able to discover the IP, it's possible that your pi is not within range of your router, you have restrictive security settings (eg. whitelisted devices), or your patchbox wifi config info is incorrect. To try again, power cycle the pi-stomp, then repeat steps #2 through #6 above.
Once you know the IP, start a new SSH session:
ssh patch@YOUR-IP-ADDRESS (password:
IP Address from above, Login:
Once connected, run the following commands to download, setup and install the software and audio plugins. It could take about a half hour.
git clone https://github.com/TreeFallSound/pi-stomp.git cd pi-stomp ./setup.sh
If all went well, now you can reboot
On first boot, after a few seconds (more than 15, but hopefully less than 40), the LCD backlight should light and the system should execute a series of hardware tests, so watch the LCD and do what it says. It will ask for you to push a footswitch, turn a knob, etc. In that sense, it's also serving to familiarize you with the controls. If it receives the input it expects within 10 seconds, it'll move on to the next. If all tests pass, it will restart the pi-Stomp software and you should be good to go.
If it fails any test, there might be a wiring issue or defective part that you'll probably want to investigate. If you just want to move on despite a failed test, run the following via your ssh client:
For optimal processing, you want the input signal to be strong enough, but not to the point of clipping. Distortion and dynamics plugins will perform less ideally if the signal is weak, and clipping just sounds like crap. When first installed, the gain is set to unity, meaning no extra gain or reduction. This might be fine for most instruments, but if your guitar has extra hot or low-output pickups, you'll want to change the gain. Here's how:
You should be able to use your pi-Stomp indefinitely without updates, but should you decide you require bug-fixes, new features or new starter pedalboards, the following should get you there.
In order to pull from the internet, updates can only be done when the pi-Stomp is in “router” wifi mode, not “hotspot” mode.
To switch modes:
Updates can currently only be done via ssh:
The pi-Stomp software changes frequently and you are generally encouraged to pull new updates.
Once connected via ssh, run:
cd pi-stomp git pull sudo systemctl restart jack
To improve the out-of-box experience we will be adding starter pedalboards occasionally. These aren't meant to be spot-on, but get you in the ballpark so you can start tweaking your own tone.
Once connected via ssh, run:
cd /var/modep/pedalboards sudo -u modep git pull sudo systemctl restart jack
Patchbox is the base operating system created by blokas.io. It doesn't change often and unless there is a specific problem, updates are generally not necessary or recommended.
When necessary, once connected via ssh, run:
If you run into any hardware or software problems, first, consult the troubleshooting guide
It's important to understand the 4 P's…
A pedalboard is a collection of plugins (effects, modelers, generators) and their parameter settings, routing, controller assignments, etc. Numerous pedalboards can be constructed and saved. Only one pedalboard is active at any given time.
A preset is a snapshot of all parameter settings for the current pedalboard. This allows for instantaneous tweaks of multiple parameters, just by changing the current preset. Each pedalboard has a “Default” preset. Others are created as needed and saved with the pedalboard. Presets are great for switching between parts of a song: Verse has light overdrive, tremolo and reverb. Chorus turns up the gain, turns off the trem, boots the mids, etc. all by hitting one footswitch (mapped to “Pre+”) or by tweaking the preset knob. The name “Snapshot” has replaced the name “Preset” from older versions of the Mod software.
Plugins (aka Effects/Modelers/Generators) are the LV2 units (similar to VST plugins) which do the sound generation or processing and are routed together with other plugins to create a Pedalboard.
The settings which control a Plugin.
Pedalboards are created and edited using a web browser via the MOD web UI. You connect to the pi Stomp over Wi-Fi. Just point a browser on your computer to
You can check the wifi mode and IP address from the System menu:
hotspot_active indicates whether pi-Stomp is available via hotspot or via router
The IP address to point your browser to is also displayed. For hotspot mode, this will likely be “22.214.171.124”. For router mode, it'll be the address space assigned by your router (eg. “192.168.1.150”)
The wifi mode can be toggled between hotspot and router modes by selecting Enable Hotspot or Disable Hotspot then clicking. It may take a few seconds to complete the connection.
Hotspot mode is generally preferred because it makes it more portable. Software download/updates require an internet connection and thus won't work in hotspot mode.
You should see something like the following showing your currently active pedalboard:
For detailed usage, see the MOD User Guide: https://wiki.moddevices.com/wiki/MOD_Web_GUI_User_Guide
Saving your pedalboards writes them to the pi Stomp SD Micro drive. No computer is required from that point while accessing your pedalboard(s) from the pi Stomp.
Please note that while you are editing pedalboards, it's best to use the MOD web UI for switching pedalboards, not the knob on the pi-Stomp. If you use the knob, it's likely that the web UI will not track correctly and any saves could end up overwriting a previous pedalboard. This is a known issue with the MOD web UI when controlled via REST. Hopefully, it can be resolved in a future update.
The pi-Stomp software setup procedure installs a set of starter pedalboards. To hear some of them in action, check out the Tree Fall SoundListen page
More examples can be found on the Mod Devices Pedalboard site. Just keep in mind that those are meant to work with the Mod Duo which includes plugins which may not be available on pi-Stomp.
The LCD shows an overview of the currently loaded Pedalboard.
Two rotary encoders are used to navigate and change settings. General encoder operation:
The upper encoder is used to browse or change the current pedalboard or preset.
The lower encoder is used to make plugin changes (toggle on/off, change parameter settings, etc.)
Upper encoder knob: click > click > select > click
Upper encoder knob: click > select > click
Lower encoder knob: select > click
From main screen, Lower encoder knob: select > long-press
pi-Stomp is intended to be a platform. MOD is the current recommended software for audio processing and configuration, but other Linux audio software, especially if it uses Jack for audio routing, might “just work”.
Here we'll explore some possibilities: Other Software running on pi-Stomp hardware
Tree Fall Sound will continue to develop both software and hardware. Software/Firmware updates are possible without reinstalling.
On top of that, all of the things the community contributes. Should be exciting.
So far, we're a company of one. My name is Randall Reichenbach.
My “day jobs” have been in Electrical and Software Engineering, but my main passion has always been music. I’ve been building effects pedals and other musical gadgets since the 1980’s (read “experienced”, not “old”). I’ve always been obsessed with tone, usability and clever features. I love my (mostly analog) pedalboard, but like many musicians, I’ve long desired the ability to store awesome presets, recall them in real time, and control the effects in unique ways. As a programmer/tinkerer, I've also always wanted to be able to code (not just tweak) my own effects.
How cool would it be to create a do-everything open expandable platform, easily modifyable by anyone not too afraid of Linux, Python, etc. ? That's the idea that got me rolling on this project. Raspberry Pi and high def sound cards along with some open source software like LV2 (plugin format) and MOD/MODEP, have finally made such an endeavor possible.
I'm creating this project because I know there are others like me that would be waaay more excited playing with a piece of gear they built and can modify by getting under the hood of the hardware and software. It's been my obsession for many months and has been a blast. I spend well over 20 hours on it every week and will continue to as long as there is new functionality and features to explore. I’m hoping others will join me in this endeavor and take this platform (or their own) to places I’ve not even considered.
Some of my music can be heard at: https://soundcloud.com/user-368371534
An extensive interview and more pi-Stomp background on Blokas Reads