I worked on Deformis, see my earlier post for details and schematic. In a nutshell Deformis is my version of Tim Escobedo’s Ugly Face in a wah shell with the pedal controlling the frequency sweep.
In the first pass I got everything working but, it wasn’t working well. The biggest problem was the pedal action and frequency sweep.
The pot I was using had a built in gear but the tooth spacing of this gear did not mesh with the tooth spacing of the rack gear. This caused the pedal action to feel really rough. It also caused the rack gear to skip which which shifted the sweep range out of the sweet spot.
To solve this problem I had to use the gear supplied with the wah shell. I couldn’t fit this on Dunlop Hot Potz pot since it had a D shaped shaft. The gear has a couple splines on its inner surface and fits a pot with a splined shaft.
I ended up using the 16mm pot with a splined shaft. With this pot the gear fits but not tightly. It slides on easily but also works it’s way off as you work the pedal. I’ll need to find a way to secure it!
I used a 3PDT PCB with an LED. This gave me a secure place to hold the LED. The wah shell has a hole for a 3mm LED above the switch.
I found some pots with splined shafts and tested out the gear. It seemed to fit and had a couple splines inside to keep it from slipping on the shaft. The smaller 16mm put doesn’t seem like it would last as long as the larger pot. But, this pot had a longer shaft which holds the gear better.
These changes helped get the pedal action and sweep closer to what it should be. It’s not quite there yet but mechanically it’s work much better than the first attempt.
At the moment the most interesting part of the sweep is a little tight. It would be nice to open this up a bit. To solve that might require changing the pot to something with a different taper, changing the size of the pot, playing with the timing cap, or more likely experimenting with a combination of all of these things.
This is a work in progress, stay tuned!
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