Deformis

Deformis

Deformis is my take on Tim Escobedo’s Ugly Face. I put this in a wah shell with the pedal controlling the frequency. The envelope was removed, and I’ve added a mix control.

Design

Here’s a schematic I came up with With some help from the friendly people over at DIYStompboxes.com.

Deformis Schematic

I wanted to add a mix control. The original Ugly Face uses an LM386 as the input stage to drive the 555. The LM386 is setup with a gain of 200. I figured I could replace the LM386 with a dual op-amp. I can easily get a gain 200 out of one op-ampm which leaves the other op-amp for mixing and output. And all in the same footprint as the LM386.

I put this on the breadboard it seemed to be working. I didn’t do a full test since it was hard to test the foot pedal with the circuit on the breadboard.

I designed a PCB in Eagle and ordered some boards from PCBWay.com. The boards came out great and were inexpensive. PCBWay’s prototyping service is $5 for boards smaller than 100mm, and you get 10 boards! PCBWay FTW! 🙌

PCBx from PCBWay.com

Build

I soldered all of the parts, including the jacks. I used sockets since this was the first build and had not been tested.

A test fit shows everything will fit the enclosure!

Now that the board is assembled I soldered the pots with some ribbon cable. The Frequency pot is a Hot Potz wah pot, the others are Volume, Mix, and Threshold. I used these nifty 12mm pots I found loitering out in my parts bin.

I wired the switch with one these 3PDT PCBs I made and a ribbon cable. With the switch wired I could test the circuit outside the box to make sure everything was working before assembling.

Everything seemed to be working. The LED is missing. I’ll add that later. The frequency sweep seems to be bunched up at one end. I found that a reverse log (C100K) pot works best. The Hot Potz pot has a custom taper. I might have to use a different pot.

Next I assembled the wah enclosure. See my post about this is you’re curious about the process.

I fit the board into the enclosure. It’s held in place by the input and output jack, nut and bolt through the enclosure.

The jacks come with a beveled washer that goes on the outside. I left this off because it seemed like the nut was sitting too far outboard, and the plug could not be inserted all the way.

I mounted the pots and switch.

At this point I realized that the order of the off board connections to the switch should have been reversed! 🤦‍♂️ I usually put them at the bottom of the board, and here they are at the top. I fixed this by twisting the cable 180 degrees. You can see a twist in the cable.

Looked pretty good and laid out very clean. On closer inspection, I notice the rack gear hits the ribbon cable to the switch. I should have made this long enough to route it round the side of the switch!

The last step was to put the knob on (I left the feet off for these pictures since I had some more work to do).

After testing everything seems to be working 🤘. There are still a few things that need to be taken care of.

The biggest problem is the pot gear and the rack gear not interfacing well. The Hot Potz gear has a different tooth pitch than the rack gear that came with the wah. This makes the motion rough. It also seems to slip sometimes but this could also be a problem with the tensioner.

The second problem, the tensioner doesn’t seem to be providing enough tension. I wrapped one cable tie around another to try to fix this.

Getting this into a functional state revealed another problem. The pot sweep seems to bunched up near the end of the travel. The most audibly interesting part end of the sweep is at the very end of the pedal travel. It’s hard to get a good feel for this when the gear is not working well, so that needs to be fixed first.

Would I call this a success? Yes! I think this went pretty well. I wanted to redesign the Ugly Face and the changes were successful. The op-amp and mix control are working. I also wanted to put the circuit into a wah enclosure. While the pedal isn’t working well, it is working and all of the issues seem fixable.

How does it sound?

More or less like the Ugly Face or Crash Sync. The op-amp gain stage is pretty hot with a gain of 200 and it has a little op-amp clipping. While this might not sound that great in your boutique overdrive here it sounds fine and compliments the square wave from the 555.

This is not finished yet, it has some potential but I have a few problems to solve.

  • The two gears do not mesh. This cause the pedal action to be rough. The gear also skips which puts moves the rotation of the pot out of the sweet spot.
  • The “interesting” sweep of the pot is very narrow. There is a tight spot where the pedal action is fun and interesting and a wide area where there isn’t much happening.

After solving the problems aboveI think this could be a very fun pedal!


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