Introduction: Proto Pedal for DIY Guitar Effects

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Designing and building your own guitar effects is a great way to combine a passion for electronics and guitar.  However, when testing new designs, I found the fragile circuit on the solderless breadboard was difficult to connect to patch cords and control the potentiometers.

The answer was simple: build a guitar pedal just for prototyping!

UPDATE:  The wire pin sockets I was using for signal in/out broke on me, so I made use of the spare holes and put in binding posts for them.  Definitely a great improvement.

Some great guitar pedal building references:

http://www.diystompboxes.com/wpress/   <- great forum

http://tonepad.com/projects.asp?projectType=fx <- well-documented projects

http://generalguitargadgets.com/ <- projects and kits available

http://www.geofex.com/ <- more good pedals and amp designs

http://www.diyguitarist.com/<- lots of pedal stuff

http://runoffgroove.com/ <- a good few more schematics and projects

Step 1: Materials and Tools

You will need:

- 20 gauge aluminum sheet
- Solderless breadboard with adhesive backing
- 3x 100k ohm potentiometers (optional)
- 1M ohm potentiometer (optional)
- 4x knobs (optional)
- 2x Bolt on binding posts
- 2x 1/4" mono cable jacks
- 2.5mm DC power jack
- 9V/12V power brick w/ 2.5mm connector
- LED and holder
- 1k resistor
- DPDT footswitch
- 2x SPDT toggle switches (optional)
- Self-tapping screws
- Wire
- Solder

Tools:
- Drill or drill press
- Sheet metal bender (aka brake press)
- Nibbler, notcher or tin snips
- Screwdriver
- Pliers
- Soldering Iron
- Scribing tool
- Center punch
- Hammer
- Wire cutters
-

Step 2: Schematic and Design

The circuitry inside the pedal is mostly incomplete, because you will be hooking up components on the breadboard on the surface.

The potentiometers and switches are all wired up to connectors so that they can be used on the breadboard however you want.  DC power coming in from the power brick is connected to the binding posts, and the footswitch controls signal routing and power.

A LED indicates power, and also indicates short circuits.

Here is a link to a higher-resolution schematic:

Schematic

The box will be comprised of two three-sided segments which will fit together like a handshake.  My plan was originally to do a 5-sided box, but that turned into major troubles and I didn't like the outcome.  I redid it doing two three-sided shapes and it was a much better result.   For this reason, a couple images depict the original design and attempt, and the rest are of the two piece that worked much nicer.  The old ones are included just for some additional information.

My template in the photos is for a 5-sided box, but it can be very easily followed for 3-sided shapes instead.  I've drawn over top of it to show the shapes and holes you need for the two 3-sided shapes.

The dimensions are 8.5"x4"x1", using 1/4" graphing paper to make everything nice and easy.  The pots, switches and binding posts are in a line across the top, spaced "1 apart each.  The footswitch and LED are 1" from the nearest side and 1" apart.  Take into account the dimensions of your breadboard before punching and drilling holes. 

Follow the image below.  It shows the flat shape of the two segments we want to make, and outlines the holes to drill.

Cut out the design and tape it to your aluminum sheet.  Mark your cutting lines around the perimeter with a sharp metal implement. A nail or scribing tool works nicely.

Mark the center of each component hole with the center punch and hammer.  Remove the template.

Step 3: Cut, Drill and Fold

First, cut out the two pieces using tin snips, a nibbler or a notcher.  Tin snips are the best route if you don't have more heavy machinery, but a big metal shear and notcher is ideal.

Once its cut out, drill appropriately sized holes for each component.  You can use a caliper to find the diameter of each, then drill with the next size up imperial drill bit.

Also drill a line of 1/4" diameter holes beneath the potentiometer holes, and file them out to make a slot for potentiometer and switch wires to pass out of.

Using the break press, bend the flanges at the end of each 3-sided piece, then make the bends to separate the sides from the top.  Repeat for the second piece.

Now, fit them together with a little bit of flexing.  Drill four tiny holes in the top panel along the top and bottom, near the corners.  The hole should be slightly smaller diameter than the self-tapping screws you have to hold the box together.  Once a hole is drilled through the top piece and through the second piece below (but not all the way through the box, of course) then disassemble the halves and drill out the top hole again using a bit slightly larger than your screw diameter.  Now you will be able to screw the two halves together firmly once everything is done.

Step 4: Paint and Assembly

Spray on a coat of paint to make it pretty, and let it cure.

Insert all the components through their respective holes and affix with nuts.  The small wire pin holes will need to be cut to shape with wire cutters and hot-glued in place from beneath.

Solder all the connectors and things together according to the schematic from Step 2.

Plug in 9V from a wall adapter and hit the footswitch, you should see the LED turn on and a voltmeter will show that 9V exists on the binding posts.  If so, great job!

Unplug the unit and screw the two halves together.  You're done!

Step 5: Conclusion

Now, you'll notice I didn't include the test pots and switches like I planned for.  I decided, circuits are so diverse, and you'll always actually need the pots later for the actual assembly of whatever you're prototyping, that maybe affixing permanent pots isn't such a great idea.  Maybe a permanent master volume control would be a good improvement, but I had a change of heart against the fixed pots.  The slots and holes are still great for future improvements and built-in features though, definitely.

This design can definitely be modified to suit any specialized prototyping purpose.  The exact same thing sans footswitch and signal jacks would be perfect as a regular prototyping platform.  Incorporating a power supply inside the unit would be very cool.  There's lots to tinker with here.

Please feel free to ask any questions.  Thanks for reading!