Ugly Face with Mix

I’m a big fan of the Tim Escobedo’s Ugly Face. This is a super fun project, sort of a. right of passage for DIY pedal makers.

The sound is unique. The best way to describe it is as a square wave oscillator that hard syncs to the guitar signal.

Since the output is either on or off and a square wave the output loses all dynamic. It’s either off or its full on square wave. There is no envelope. My idea with this project was to add a mix control to mix the input signal with the square wave.

I also had a secondary goal of getting away from the LM386 used in the original. I love this chip. It’s the easiest amplifier you can use and makes a good choice for the original design.

The LM386 has a few draw backs. It has a gain of 20 to 200 which is plenty for a lot of applications but it doesn’t have the range of gain that a regular op-amp has. It’s also hard to set the gain. The input impedance is not great. It only provides one amplifier in an 8 pin DIP.

I replaced the LM386 with a dual op-amp. Now I had two amplifiers in the same space. I could use one for the input and the other for the mixer.

I had some PCBs made through The prototyping service is inexpensive and fast. The boards were great quality.

Deforms (Ugly Face with Mix)

I designed these boards with the off board connections at the bottom and the pots, jacks and LED mounted to the board. This made for a nice clean build.

I needed a B10k pot but didn’t have one with “legs” so I soldered some wires onto a lugged pot.

This first build had a problem. I had a missed a connection from pin 6 on the 555 to the frequency control. On the initial test the basic sound was there but the Frequency, Envelope, and Threshold knobs were not working. I spent some time with the multimeter and the schematic until I spotted the problem.

The fix was not hard. I opened the box pulled everything out and ran a jumper from pin 6 to the junction of the 470 ohm resistor and the LDR. I had designed the board with the off board connections at the bottom edge, this made the process of easy as a I only had to un solder the power connections at the top and remove the nuts and washers on the pots.

After the fix everything was working! The mix knob adds something to the sound. Not huge but there is a little bit of dynamic, you turn down the square wave craziness, mostly, it’s always there in the background. I’m not sure if this op-amp distortion or if the 555 is bleeding through the mix control? I’ll need to experiment with this some more.

I wired it up with a 3PDT PCB and a ribbon cable for a clean and easy build.


Would I build this? I’d consult with your band first the Ugly Face may be an acquired taste for some. Turning this on in the middle of a song could be like walking into room wearing a strong cologne.

More seriously, the Ugly Face sound, and it’s similar to the Big Muff in this respect, lacks dynamic. There is no envelope. The sound either on or off. The result is that even though by itself it’s a loudest most obnoxious square wave fuzz you’ve ever heard, in a back context it just disappears. Seriously try it. Unless it’s a lot louder than than everything else it drops out for lack of an envelope.

Back to the question of would I build this. If I was planning the play with this effect I’d build this one. The mix control adds more options for sound and brings a little more dynamic envelope making this more flexible than the original.

If you’re just building this as part of your DIY journey, you could build this, or you might want to build the original as window into DIY pedal history.





One response to “Ugly Face with Mix”

  1. […] LM386 for a dual op-amp. I used one op-amp to replace the 386 and the other to add a mix control. You can read more about Deformis here. This version fixes an error in the original […]

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