Building a Wah Pedal From Scratch #2

Created 6/24/05
Last updated 9/30/06
By Paul Marossy



Having some success with my first DIY wah project , I thought it might be worth a try making a simpler version of a DIY wah - keeping the same concept with utilizing easily obtainable parts and using the most basic of tools. In building this wah pedal, I used nothing more than a hacksaw, hand drill, Dremel Tool and various files. This particular wah project is built around the Maestro Boomerang circuit.

I got the idea for this wah after seeing a picture of a DeArmond Weeper Wah. The wah shell will be based on this RadioShack plastic project enclosure measuring 8"x3"x1" (Part No. 270-1808). I am using this as a prototype. For a DIY wah pedal that will last for years, something like a die cast Hammond enclosure would work nicely. However, I can not find anyone that makes a die cast enclosure that measures 8"x3"x1".

The first step was to cut some slots into the enclosure to receive the foot paddle spindle assembly. The slots are 3/4"x1/8" and were cut with a Dremel Tool equipped with a cutting wheel.

Here is the foot paddle spindle bracket. It is made from a piece of 3/4"x1/8" aluminum. The large holes are 7/16" in diameter and the two smaller holes are for the screws which will attach the bracket to the enclosure. It was made simply by cutting it to length with a hacksaw, and then cutting the angles with a Dremel Tool equipped with a cutting wheel. I bent the piece using a vise and my hands.

This is the foot paddle spindle bracket in place with the spindle inserted. The spindle is made from 7/16" diameter aluminum tubing. The rest of the wah will be built around this basic piece.

This is the foot paddle spacer. It's cut fo fit exactly between the risers on the bracket and will serve two purposes - it will eliminate any side to side movement of the foot paddle and also allow for free movement when rocking the foot paddle.

This is how the foot paddle spindle bracket looks from the inside of the enclosure. When the bottom cover is on, this piece prevents the plastic enclosure from getting twisted or squashed when rocking the foot paddle. When this piece is bolted to the enclosure, it makes everything suprisingly sturdy. Time spent on the project so far is 1-1/2 hours.

Next, I drilled a couple of holes in the foot paddle bracket and enclosure to allow for easy attachment of the foot paddle to the spindle.

Here is a view showing the foot paddle attached to the spindle. I used nylon threaded nuts here so that once they are tightened, they won't come loose.

This is how the wah pedal looks after about three hours of effort. The foot paddle is cut from the same 1/8" thick piece of aluminum that I used for my first DIY wah project. I think this is a far superior spindle arrangement compared to my first wah project.

Here I am using a dead 3PDT switch for testing the fit of the switch inside the enclosure. The U-shaped piece of aluminum should prevent the enclosure from flexing with operation of the foot switch. This piece in conjunction with the foot paddle bracket should make the pedal feel pretty solid in spite of the base being made of plastic. My testing so far seems to indicate that it will work OK with reasonable use.

This wah pedal will follow the basic layout of the typical wah. The battery will be below my self-designed PCB, and the pot and footswitch arrangement will be similar to a CryBaby/Vox wah pedal. I'm just about ready to apply the internal shielding, but first I have to work out the pot mounting arrangement.

After I figured out exactly where the pot would be mounted, I decided that the shielding needed to go on next, so I proceeded to apply the aluminum shielding, which is called "metal repair tape". Basically, it's aluminum duct tape, and it works pretty well for shielding things such as this plastic enclosure. The foot switch bracket provides electrical continuity between the two pieces. I have also etched the PCB and have it partially populated. I spent about an hour on this step.

While I was waiting for my Fasel inductor and the rack & pinion parts to arrive, I decided to determine what the foot paddle travel should be and how to control it. This piece will limit the foot paddle travel at the heel end. At this point, I have spent about six hours on the project - not too bad considering I'm doing R&D while building this thing. Now, on to the pot mounting...

After a good nights sleep, a thought came to me about how to do the pot mounting. A simple little offset bracket that is attached to the footswitch bracket does the job effectively.

Here is another view of the pot mounting bracket. I am using a standard 1/2 watt linear Alpha pot for now, as I don't know where to get a heavy duty 25K pot similar to the 100K ones used in the typical wah pedals available today.

A couple of pieces cut from a 3/4"x1/2" L-shaped extruded aluminum angle will hold the rack.

Here is how the assembly looks when installed in the enclosure. This step took about 2 hours to get things to my liking.

With the pot mounting worked out, there was nothing to prevent me from wrapping up the project. Here I have finished all of the wiring and worked out the pot rack and pinion arrangement. It took a few trys to get it right - the challenge being limited height in the enclosure. At the lower part of the PCB, you can see the yellow reissue Fasel inductor I used.

This is an overall view of the interior of the completed project. When the bottom cover is on, the entire enclosure is shielded. The battery compartment is lined with some self-adhesive 1/16" thick foam rubber to prevent the battery from moving anywhere and also to keep the battery snap from shorting out on the shielding. There is a also some pieces on the bottom cover to prevent any possible shorts.

This is how it looks when all buttoned up. I decided to paint the exposed aluminum parts flat black. It makes for a nice looking project. Total time spent building the project is somewhere around ten hours. A lot of that time was spent on the fly finding the best way to do what I wanted to accomplish. That doesn't count the time spent pondering how to accomplish certain things and debugging it.

Here's a front view. For the opening at the pot, I used measurements taken from my CryBaby and cut the opening to those dimensions. Getting the footswitch activation point worked out was a little problematic. The two pieces above the foot switch helped to get it just the way I wanted it. There is a cork pad at the point where the foot switch meets the foot paddle.

Here is a side view of the rack and pinion arrangement. One could find a way to install some rubber bumpers to prevent the footswitch from being unintentionally switched with movement of the foot paddle, but so far it hasn't been a problem for me. I had to cut a small hole in the bottom cover to relieve the rack to enable proper switching as the rack needs just a little more room in the maximum up position. With the paddle in the full forward position, the tip of the rack is perfectly flush with the bottom of the enclosure. It just works!

This is the hole I cut in the bottom of the enclosure. This is how it looks with the foot paddle fully depressed, at the point where no more travel is possible.

To officially complete the project, I made this little nameplate to put on the front. It gives it a nice touch.

Here is a size comparison between my first DIY wah project, my Vox wah and this new project. This is a really compact little wah! I personally would have no problem using it regularly, as it is really quite sturdy and reliable.

The objective of this project was to come up with a simpler DIY wah project than my first one, which really is a hardcore DIY project. This project is very simple in comparison, and I think is within the grasp of the average do-it-yourselfer. I also wanted the circuit to be fully enclosed and shielded, which I have accomplished. The hardest part of the project is fabricating the ten aluminum pieces required, all of which can be created using the most basic of tools. At first, I thought that this plastic RadioShack project enclosure that I used would be kind of flimsy, but it is amazingly sturdy when everything is together. As for the circuit, it sounds really good to my ears. When I tested it for the first time, it didn't work - the volume was very low compared to the bypassed signal and the wah effect was intermittent. One of my problems was that the PCB was shorting out on the shielding, which was fixed by placing a thin piece of cardboard from a cereal box in between the foamrubber pad below the PCB and the PCB itself. The main problem was that I had the connections to my homegrown battery snap reversed! I fixed that and then it worked beautifully. Actually, I'm surprised that it even worked at all - usually, the battery gets hot if you reverse the polarity, but it didn't in this case. That made troubleshooting a little more difficult because I was looking in all the wrong places. Then I decided to check the power supply, and it was the first thing that I found - embarrassing, but true. Anyhow, I can see this wah being on my pedalboard once in a while!

Original Maestro Boomerang PCB Layout (BG-2)

My Maestro Boomerang PCB Layout (BG-1)

Maestro Boomerang Rehoused