Distort-o-Matic XI revisited

I build this Distort-o-Matic XI a few months ago. It had a few problems. I got it out and tried to solve some of the issues. I’m working on a new PCB. I ordered the original PCBs from PCBWay.com. They have a special deal for prototyping, you get 5 or 10 boards for $5. Since it costs the same I always order 10! Which means I have 9 mores boards left over. I hate to let these go to waste.

Even though there are some imperfections I thought I could get this board to work better and make a few improvements.

First the “Bias” pot should have been a trimmer. I found a funky old trimmer that fit the footprint of the pot on the PCB if I bent the legs a little. The enclosure still has the hole for the pot but this enclosure already had some extra holes.

There was a lot of noise. The original circuit had no power supply filtering! There was no room to add this to the PCB. I took an old 100n cap and soldered it across the legs of a 100µ cap. Then soldered this across the DC power jack. This cleared up a lot of the noise.

It’s a little ugly inside the box but the noise is gone and bias pot is now an internal trimmer.

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