Introduction: DIY USB Pedal Board for Live Looping

About: Warthog-faced buffoon.

I wanted to try out live looping, but I didn't want to spend $200+ on a piece of gear that might never make it to a gig. So I put together a fairly useable rig using a netbook, a USB audio interface, and this homemade pedal board. 

Live Looping:
It's a somewhat gimmicky but potentially amazing approach to musical performance: you make a noise into a magic box which records the noise and plays it back repeatedly, then you make another noise and another, and pretty soon you've piled up several noises and they are playing at the same time and you didn't have to grow extra arms or clone yourself.

Here are a couple of folks who have really made some cool noises using this technique:
Casey Driessen:
Walk Off The Earth:

These folks use big piles of nifty gear, but I didn't want to invest in a piece of equipment until I had the chance to experiment with loopiness. Enter Mobius: Free (donations accepted), robust looping software. I got it running on my trusty little workhorse of a netbook (along with my USB audio interface), and quickly noted 2 things: 1. Mobius is awesome, and 2. there is no practical way to use it for live looping without foot pedals. So I decided to make them.

Step 1: The Plan, Materials

Exploiting the fact that Mobius accepts keyboard input, I decided to build a pedal board using a busted USB keyboard and some miscellaneous hardware.

This is far from a new idea, lots of folks have done it; here are a few 'ibles using similar principles, dealing with pedals and keyboards and whatnot:

Basically you are taking a keyboard and replacing a few of its little buttons with bigger buttons.  

Similar pedals have been made to trigger MIDI events, scroll through sheet music, and enable users to do any number of other swell things with their lower appendages. This design could be easily adapted to any of those uses. Have a laser cutter or CNC router? Then your pedals will look way cooler than mine!

-thick plywood (I used 3/4" but thinner would be fine).
-thin plywood, les than 1/4" (I repurposed a sliding panel from a defunct cabinet)
-other wood scraps
-PVC pipe, cut in half lengthwise
-momentary pushbutton switches
-logic board and USB cable from a USB keyboard (these usually die of mechanical problems, so the parts we need here are fine)
-insulated copper wire
-springy electrical contact thingamabobs, salvaged from an old learning-about-electronics kit (optional: you could just as easily solder all your connections together. I used these because at first I wanted to make a fully reconfigurable board. Gave up on that idea, but the springy things remained).

-saws: circular, jig
-hot glue gun
-Gorilla glue
-soldering stuff
-wire cutters, strippers
-paint & brushes
-volt meter (continuity tester)

Note: I will be providing no real measurements, because I didn't do much measuring: it was all eyeballing and trial and using one thing as a template to trace the next thing so that both things are the same size.

Step 2: The Build

I made the thick plywood base, shaved an approximate angle off of the front edge for the hinges, and cut the sides and pedals out of thin veneered plywood.

The sides are attached with short plywood screws. The stock screws that came with the hinges were a bit too long and wanted to poke through the thin pedals, so I used much shorter screws I had in the junk drawer, fortified with a little glue.

I cut a top panel to match the top edge of the side panel, overlapping the pedals so they stay put.

The back panel has a small notch for the USB cable to escape.

The back and top are one piece and can be easily removed from the base by pulling out a few screws, for access to the wiring and such.

Step 3: The Guts

My initial goal was to make all of the pedals completely reconfigurable, so I (or my kids) could easily switch around some wires and end up with five new keyboard buttons. I had a handful of little springs scavenged from an old electronics experiment kit that would have been perfect for attaching attaching different  wires to each other to "make" new buttons. I also planned to make plexiglass "windows" above each pedal, under which I would slide a piece of paper with the button or function printed or drawn on it. But as the soldering progressed, the wires became so unruly that I abandoned reconfigurability. If I were buying the materials instead of using what I already had, I would have gone with much smaller gauge wire. 

In any case, once reconfigurability was abandoned, I focused on just soldering the points required to make the specific buttons I guessed I would need for basic operation. Here are the pre-configured keyboard bindings in Mobius:
...and here's what I used:
R: press once - Mobious starts recording. Press again - recording stops, looping playback begins
Arrow keys: right, left, up - for moving between tracks and the loops within tracks
U: mutes a track.
One button that might be worth adding: F1 or F12, to reset or clear all of the loops. It's not so bad to reach over and hit the key with your hand, but it would be nice to be able to do it hands-free. Maybe just a button sticking out of the side? still kickable, but no full-sized "pedal" needed.

I figured out which wires to fiddle with using some of the methods described in the links I provided a few steps back: I first determined the location of the desired key on the two sheets of transparent plastic from the keyboard - each key has one circular spot on each sheet, and the computer "sees" a key press when the two circles are smooshed together to make a momentary connection. I placed one lead from a continuity tester on one of the two circular pads, and gently dragged the other lead across the solder connections on the circuit board. When the needle jumped, I knew I found the right solder point. I repeated that process until I had found all of the solder points for each key.

Step 4: Putting It All Together

I soldered each wire to a post on the appropriate pushbutton switch, so that the wires for each key terminated in a switch that shorts them together when pressed.

To get the pushbuttons at the right angle for the pedals to land on them squarely, I mounted all five buttons to a piece of PVC pipe I'd cut in two, then screwed the assembly to a wooden block. This, like many of my methods, was mainly a math-dodging maneuver: it allowed me to eyeball the correct angle instead of determining it through honest measurement.  

Springs were added so the pedals would bounce back up after each press, and the narrow top panel keeps the bounce in check.

I drilled holes in the PVC pipe to match the mounting holes on the circuit board, and zip-tied the board to the PVC.

I carefully routed and stuffed all the wires in so they wouldn't contact each other (relatively easy since the wire I used is stiff enough to bend into place and stay put), and closed up the back panel.   

Step 5: Aesthetics, Trial Run

I painted various surfaces with glossy black, effectively hiding some of the shoddy workmanship. The veneer on the the back and top panels was still looking decent so I left that showing.

I added wooden disks with symbols on them to identify the pedals.

All in all it wouldn't look too silly if I were bringing it to a gig, and that's a high enough standard for me, coming as I do from a long tradition of gigging with silly-looking home-made crap:

Now it works. So now all that's left is to try it out, right?

I hooked up a Shure SM-58 and my guitar into my USB audio box, fired up the netbook with Mobius, plugged in the pedal board, and started messing around making noises. Preliminary findings:

-Okay, this is the hard part. It's clear that I need to grow a few more wrinkles in my brain to be able to think about music in "live looping" terms. Casey Driessen makes it look so easy!
-Happily, after you set the first looping noise, it's easier than I thought it would be to play another one on top of it in time, because you can jump over to a new track, press R, and the new loop is not recorded until the first loop comes around. Similarly, when you hit R again to stop that new loop "early," it waits to play back until the right time.
-you can make a loop that's twice as long as another one, and they will live in peace

baby steps: I started with a song that I know has a part that repeats a lot: the Who's "Eminence Front." 
I recorded a bass drum sound from a crappy little conga I have, and layered in some cymbals and hi-hat courtesy of pointing the mic at my pocket full of keys and change and tapping with my fingertips.
With the drums looping away, I hopped over a track and played the two-note bass part.
Then I did the riff that repeats throughout the song.
Basically that worked, and I could play some percussive rhythm guitar over the tracks I'd recorded moments before and sing!

That was really fun and promising, but then it all fell apart at the bridge: I needed to mute the bass part and the riff, play the bridge intro, then start the two muted loops again... and that's going to take practice!

However: Bill Withers' "Use Me" might just work... I think that's next.

No video of the looper in action yet, but here are some other noises I make:, more here: and here:

Thanks for reading!


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