I design and build custom stomp-box style expression pedals. My analog pedals tend to follow a convention of modular circuitry while the digital pedals are much more varied in their applications and designs. This post introduces some of my stomp-box projects in both the analog and digital realms.
Modular Stomp Boxes
This work is directly inspired by the “Fuzz of 1000 faces”, the work of Randofo (the runner of the instructable design community), and the instructable community as a whole. In many ways, this work can be seen as a spiritual continuation of the Fuzz of 1000 faces project.
Modular Stomp Boxes are stomp-box style distortion pedals that let the player choose between hundreds of distinct circuit combinations to find the perfect sound. Many guitar players collect distortion or fuzz pedals because different brands, or models, have different sounds. While sometimes the sonic variance is inherent to circuit topography, often the circuitry is nearly identical between pedals of the same distortion type: occasionally the only difference between two pedals is the make and model of a single transistor.
With my performance background primarily spent as a bassist using only careful equalization, gain structuring, and occasional light compression to craft my sound, most of my experience working with effects has been inside of computers. As a programmer, and electronic musician, I am used to working with effects that allow for a large range of tonal variety. This is especially true when compared to the inherent limitations of analog effect units: which generally have a dedicated use with very specific tone shaping characteristics. As a guitar player, or bassist, I want more flexibility in my hardware.
By exploiting the wide range of components available for reasonable prices from various manufactures in the now global market for electronic components it is easy to find a dozen transistors or capacitors all designed to perform the same task but with slightly different results. It is any true musicians desire to carve out their own individual sound. To be able to be distinguished from everyone else to sound recognizable. Modular FX pedals such as the Indecision Fuzzes are able to provide the player with hundreds of different circuit combination that each have a unique sound allowing them to sample all the possibilities and choose the sound that really is right for them.
“Why not create a pedal that contains many different values and makes of different components that can be interchanged for different sounds?”. By including many different possible transistors, capacitors, and other sonically crucial components onto a single board that uses rotary knobs to ‘hot swap’ the components, we are able do just that.
The Indecision Fuzz
I decided to create four modular stages within a relatively simple diode clipping fuzz box. The input capacitor is the first stage, different values, I used 6 caps rated between .001uf through 10uf, has a noticeable effect on the incoming tone. Higher value capacitors tend to allow more bass energy through to the next stage while the smaller values will only let the higher frequencies pass. These values allows for most of the audible range through and work well for either guitars or basses. The circuit uses one BJT transistor to amplify the signal before sending it through two diode arrays (which attenuate the signal) and lastly sending it out of the unit and into the next effect or your amplifier. The transistor is the next component that is modular as well as each of the two diode banks.
After purchasing my needed components from my favorite electronics store I proceeded to solder everything into place. I assembled the board and all of the components, tested the circuit and most everything worked. I noticed considerable volume variation depending on which transistor was selected, noticeable clicks and pops while transitioning between components as well as a less than noticeable change in output tone when some diodes were switched out. Perhaps the most disabling factor to this version was its sheer size. The circuit board with all four rotary knobs, three pots, two 1/4″ jacks, 9v battery and DC power plug, poorly chosen gauge wire (22) and unnecessarily long component lead wires resulted in a conglomeration far to bulky to stuff into any standard stomp-box enclosure. Knowing the ongoing nature of the project compounded by by need to wrap the exposed components in metal of some kind lead me to haphazardly cannibalize an old internal PC CD-ROM burner creating a janky case to house the first version of the Indecision Fuzz.
Here is a short video showing the final results.
The second version was created in a much more proper fashion using EAGLE for the schematic design as well as the board layout. I kept the same design as the last version but did fiddle around with some components, switching out the main trouble components. The end result is nearly identical with a few differences. By using proper layout software (if not proper technique) did allow me to reduce the size of the board by about 30%. Additionally, I completely redesigned the wiring of the pedal’s input jack, battery, and DC jack to allow for better power conservation features.
This includes the battery being disconnected when the power jack is occupied or if there is no input cord occupying the jack as well as an LED which shows when the effect is engaged and true bypass when the effect is disengaged. I enclosed the second version in a relatively old splitter box for monitors which was deep and wide enough to accommodate the, again large profile of the circuit. I was hoping to be able to fit the circuitry into a Hammond 1590BB size enclosure but there simply were too many components. I had an extra metal box that housed a video router, tore out the insides and replaced it with the pedals circuitry.
Having learned more about how to properly layout simple circuits, and the usage of appropriate package-sets for designing boards i was able to create the third, and more streamlined version of the Indecision Fuzz. This time i started the design process with the enclosure. I chose the 1590BB size metal enclosure box for the pedal. The 1590BB is a relatively common size enclosure for large more complex stomp boxes but is still about half the size of the original CD-ROM drive I used for my first enclosure. I printed out true-to-size cutouts of the rotary knobs and pots I wanted to use and started to experiment with placing them on the enclosure trying to find a configurations that would allow for the most control while still leaving room for the battery and circuit board to live. I found that if I abandoned one rotary knob and one potentiometer i would be able to have enough room for everything to fit, given i am able to reduce the size of the board significantly. I chose to place the rotary knobs in the back of the enclosure, where the DC adaptor usually is. This freed up more space inside while also simplifying the UI.
While examining my past boards I noticed that the two diode arrays (consisting of a total of 24 diodes) consumed nearly half of the boards size. I removed the diode arrays, and assigned my newfound extra rotary knob to the output Capacitor. I then fiddled around with a few resistors allowing for larger gain values from the transistors, to give back some of the grit the diode arrays created. I changed the values of my capacitors in both the input and output arrays to accommodate a wider range of values and thus tonal characteristic. Now that the diode arrays are gone I am also able to remove the pot that blends between the two arrays allowing me to meet my quota.
Over the course of several months the Indecision Fuzz project has come a long way and is temporarily on hold(not dead). on Fuzz project evolved into my work on designing a BeagleBone powered digital FX pedal, this project is coincidently my BFA final project at CalArts. You can expect more info in 2015.
Before my work with modular circuitry I began by designing simple distortion, overdrive, fuzz, boost and tremolo pedals. This tremolo pedal was my first attempt at making a durable lasting FX pedal myself. The circuit is unremarkable just a generic 555 time circuit modulating the amplitude of the incoming signal. The circuit is a combination of several online tutorials and, to be honest, only works half-way properly. Additionally, unintentionally, the pedal doubles as a cliche sci-fi synthesizer as the circuit will oscillate on its own if no input is present. The fix for this issue is easy, its just a matter of upgrading the input and output circuitry to include a true bypass but I consider the project closed, it served my learning quota. I spent a good deal of time ensuring that everything would properly fit into the enclosure. I wrapped the circuit in cellophane to isolate it from any possible shorts and was able to fit everything nicely inside.
In fact, the primary goal in constructing the Tremolo pedal was just at, construction. I used a professional aluminum enclosure that is a standard size for FX pedals. I added cardboard (I use cork board now) between the components and the enclosure to better fasten the components. I added a proper power LED, an option for using regulated wall power (9v) in place of an onboard battery. I attempted to drill my holes evenly and intelligently design all the inputs outputs and throughputs. It is by no means a professional job, but was an important project as in it helped to set a standard for my construction methods.
Here is a really spotty video demonstrating the pedal as it was intended, a Tremolo Pedal.
Much more interesting, in my opinion, is this video showcasing the Tremolo Pedal hooked up as a simple synthesizer. I leave the output plugged in but remove the input and the circuit oscillates on its own, it can me modulated to provide varied pitches and rhythms. Fun stuff!
I collaborated in late August of 2014 with composer Lucas Martin to build a digital stomp-box capable of sending bangs into MAX MSP. He wrote a piece titled Undoing, Moving: I’ll Go On for solo bass and electronics in which the player would have the option at certain points in the piece to press the pedal to trigger certain signal processing and recorded sounds. After talking about the possibility of using unconventional means to trigger the bangs we settled on a simple two button design. Lucas wanted the device to have the same strait forward interaction found in traditional pedals. The BangBox was born over the following weekend.
The BangBox is designed to be as simple and harmess as possible. It has two stomp switches on the top and a USB cable for interfacing with Max patches being run on a host computer. The Max Banger is not limited to only interacting with MAX MSP, as a matter of fact, with some simple code modification it can be used with any other programming environment or DAW. The pedal worked as planned for the performance banging max as needed. The piece was beautifully composed and performed, you can watch a clip from the performance below (ironically enough I did all the filming as well as I was working the Live Webcast for the concert that night).