Building a Wah Pedal From Scratch


Last updated 6/14/05
By Paul Marossy

 

 

This project started out as a curiousity about how the Colorsound inductorless wah circuit might sound. I built this twin-T wah circuit and decided that I liked it, but I didn't have an empty wah shell lying around, so I thought it would be a challenge to make my own wah assembly out of easy to obtain parts that you can get at your local hardware store. I have seen some people's DIY wah/volume pedals, and a lot of them look rather primitive not to mention ugly! I chose to try and find something that looked good, was strong, reliable, and could be be made using the most rudimentary tools. Obviously, there are some real challenges presented in attempting something like this, but I like a challenge in these sorts of areas.

Outlined below are the steps involved in building this wah project. It was built using nothing more than a vise, hand drill, Dremel Tool, hacksaw and a couple of different kinds of files.



This started out the way most of my other original projects did - an idea. I woke up the day after I built the circuitry, and had this concept of how to make the wah shell. I made a quick sketch of my idea before I did anything else.

The key to the whole thing are these brackets - everything is pretty much built around them. They are constructed of 3/4"x1/8" aluminum. I cut them to the lengths needed and I bent them to my requirements using a vise and muscle power. The bottom pieces are 3/4"x1/2" L-shaped extruded aluminum. About 45 minutes worth of effort.

I made the foot paddle from a 10"x10"x1/8" aluminum plate that was given to me. I cut it down to get a 4"x10" piece. Next, I had to sand off the black paint that was on it. It took about 20 minutes to completely remove the paint.

Here I have sanded the foot paddle down to bare metal and have also cut the bottom piece, which is composed of a piece of 1/4" plywood painted flat black. All those holes on the foot paddle will be covered up, so I am not worrying about that at this point. Now it's starting to take shape. So far, I am about 2 hours into the project.

These are the basic parts. The main brackets are now fastened to the plywood and the L-shaped pieces form the edges of the base of the shell while stiffening up the whole assembly. The two short pieces will hold the foot paddle spindle in place.

Here the foot paddle spindle is being tested for fit. Overall size will be 4"x10"x2", roughly the same size as an Ernie Ball volume pedal, but a little lighter. When assembled, this is quite strong due to the nature of the construction. This part took about an hour, mainly because I was trying to optimize things as much as possible.

Here I am determining the best way to attach the spindle to the foot paddle and also what kind of clearances will be required for proper operation. I spent probably 1/2 an hour on this part.

Finally, the basic assembly is together. The "test jacks" are in place and the circuit is ready to be installed. But first, I have to tackle the mounting of the pot and bypass switch. As I am writing this, ideas are coming to me on how to go about those items. At this point, I am about 4.5 hours into the project.

Here is a closer view of the spindle assembly. I found that the end caps on the spindle help to make the foot paddle operation smoother and will also, in theory, help keep the grease from the spindle contact area from getting on anything. So far, I have spent about 6.5 hours on the project.

Here is a better view of how the foot paddle is attached to the spindle. There is a spacer and a nut between the spindle and the foot paddle to provide adequate clearance from the brackets. The nuts on the other side of the spindle are equipped with nylon bushings to prevent them from ever coming loose. On the other side of the paddle, the screws are countersunk to provide a flush surface. So far, the operation of the foot paddle is smooth and predictable, with no binding. Now on to the hard part: determining footpaddle/pot travel and the mounting of the bypass switch...

Having the bulk of the difficult mechanical stuff out of the way, I decided to take a break from that and concentrate on the electronics portion. My self-designed PCB fits perfectly. A happy coincidence since I didn't really do any planning beforehand with regard to the physical size of the board, I just made it as small as possible. At this point, I was still contemplating how to do the pot arrangement - I had a few ideas, but didn't really like any of them. This step took about two hours.

Here is how the PCB looks when inside the fully assembled wah, looking in from the front of the pedal. It sits on some spacers and is attached to the the plywood base. I also installed some aluminum shielding under the PCB. A wire is connected from the PCB ground to the 1"x1" angle piece where the output jack is. Since the bulk of the pedal is metallic, I think the the circuit shouldn't have any problems with extraneous noise.

I also installed a control knob next to the input jack for a little mod that I instituted - a pot on the emitter of the transistor to adjust the Q softness/sharpness as desired. I used a 10K pot to start with, but later changed it to a 500 ohm pot because a 10K pot was simply too large a value. A 1K pot would also be a suitable choice. For the rest of the components, I used a 2N5089 transistor, metal film resistors and mylar film caps.

I woke up from a nap and had another brilliant idea about how to do the pot arrangement. I was leaning torwards the way it's done in the CryBaby wah, but I thought it would be cool to do something different. After about 1.5 hours of effort, this is what I came up with - a piece of 1/8" thick aluminum cut at a specific radius to follow the rotation of the pot's gear.

The pot itself is attached to the bracket with a 1"x1" L-shaped piece of aluminum, cut and notched to receive the pot gear in the same manner as the CryBaby wah. I know, you might be thinking "how the heck did he make that work?!", but it's really not as hard as it sounds. Believe it or not, it is actually possible to make adjustments to the pot travel without dismantling any part of the pedal - only a little bit of muscle power is required.

This is a side view of the gear arrangement. To find the curve required, all I had to do was measure the straight line distance from the center point of the foot paddle spindle to the valley between two adjacent gear teeth on the pot shaft gear as it would be installed in the fully assembled wah. Then using that measurement for a radius, I used a compass to draw a short curve and cut my piece of aluminum to that same curve. Next, I eyeballed the teeth with an extra fine point marker and proceeded to cut the gear teeth with my trusty Dremel Tool equipped with the ever so handy cutting wheel. I had to do a little bit of filing and fine tuning, but it pretty much worked on the first try. The foot paddle throw is just a little more than my CryBaby, and almost as smooth to operate. The actual pot rotation is about the same as my CryBaby as well.

Now that I was finished drilling holes in the foot paddle, it was time to cover it. I chose to use some self-adhesive 1/16" foam rubber on it which covers up the holes and gives a non-slip surface on the foot paddle.

Here is how it looks from the right rear quarter. Now all that is left to do is create the bracket that will hold the bypass switch in place. The electronics are basically exposed in this arrangmement. Not so much a problem where I live since it's so dry here in the desert. I am really concerned more with possible RFI/EMI problems, but being a low gain inductorless circuit, I don't anticipate that being a real problem since the circuit ground is physically connected to the wah's metal parts and because of the shielding that I placed underneath the PCB. I have a hunch that it will be fine as it is mostly surrounded by metallic parts.

Here I am using a paper template to determine the bracket shape and switch placement in a manner similar to what I did in my Shaka Tube in a Hammond 1590BB enclosure. I have now spent about 10 hours or so on the project, maybe a little more counting all the planning and stuff.

The footswitch is now in place. I had to abandon my original idea for the bracket shown in the previous frame because I don't possess the proper tools to make it per the template I made. So I found another way to do it. I used a mini DPDT switch that I had lying around for the bypass switch. This last step took about 1.5 hours, only because the first two attempts at making a bracket ended in failure.

The foot paddle contacts the footswitch actuator at just the right position. About the same amount of effort is required to switch it on/off as it takes for my CryBaby. You can also see in this picture that the pot bracket also serves as a stop for the foot paddle and helps to prevent the plastic gear from getting mangled from aggressive use.

Here is a view of the footswitch and pot bracket from the opposite side. Not shown in the pictures above are the graphics I made to mark the input/output jacks and the "Q control". The final thing left to do was to place some rubber feet on the bottom corners. And with that, the project is now complete! Well, almost. The last thing that needs to be done is the installation of a cross brace between the brackets at the front half of the pedal to make the whole assembly as rigid as possible. That will be a minimal amount of effort.

Here is one last view of the back showing the relationship between the switch bracket, the pot and the rack and pinion assembly.

The cross brace has now been installed, and it took right around twenty minutes to make and install. This should prevent any eventual problems if the plywood bottom should warp at all, and prevent any twisting of the brackets when the foot paddle is operated. Well, I guess this officially completes the project. I already have some new construction ideas to try out for my next DIY wah project, which will be based around the Maestro Boomerang circuit.

Some thoughts about this project. As has been said, building a wah is easy when it comes to the circuit part - but the mechanics are the difficult thing. Obviously, this would not be the way to mass produce a product, but it has given me some insights into the design of something like this and the challenges it can present. Knowing what I know now, I would probably build a wah a little differently from the methods I chose to use. That's really only talking about the foot paddle spindle arrangement, which would probably look something very much like the way it is done on the Ernie Ball volume pedals. Anyhow, I can see why the typical CryBaby/Vox wah shells are made from a casting and why the foot paddle arrangement is how it is. There are also other ways to rotate a pot shaft, as the Colorsound wah shows us. The method employed on the Colorsound wah was clever - it used a slotted cam style actuator. A fixed lever is attached to the foot paddle which goes up/down into the body. There is a black plastic slotted lever connected to the pot that pivots and slides along a pin in the foot paddle lever, which then turns the pot. Here is a side view of that assembly. The only disadvantage about the slotted cam style actuator is that it can create a long foot paddle travel, but on the other hand, can give you full rotation of the pot, unlike the CryBaby/Vox rack and pinion arrangement.

As for the sound of this Colorsound inductorless wah circuit, I think it sounds really nice. It is a little mellower sounding wah compared to something like a CryBaby, but with a real nice feel. I'm not real sure about the actual pot taper used in the original, but it has a good range between high and low with my 100K Hot Potz. It seems to really come alive around the maximum treble postion. The response of the pedal is different than my CryBaby or Italian Vox wah, the sweep is really noticeable with a clean guitar sound, but less distinguishable with distortion. It also seems to be more responsive when you are playing between the first position and the 12th fret as opposed to above the 12th fret region. None of these traits are severe enough to bother me, though. So far, extraneous noise hasn't been a problem.

This was really just a project I did more or less for fun, but I created this page in the hopes that it might help someone, somewhere to build their own wah pedal.



Colorsound Wah PCB Layout