Brach,
It’s been awhile since I assembled my Quaverato and I confess that I’m not sure what the “pwm rail” is. I reviewed the assembly instructions but it didn’t pop out at me. I guess I could send the pedal to you so that you could have a gander, but I live in Hawaii! I seem to remember that I initially assembled the Quaverato without placing the paper sheets under the pots to insulate their backs from the components. I opened it up again and inserted the sheets and that reduced the noise considerably. I then slid in some flattened heat-shrink insulation material thinking that that would help even more, but this didn’t reduce the noise anymore than the the paper separators already had.
I could attach some photos of both sides of the board so that you could at least have a look, not sure if that would help—I guess I’d have to upload them to an image hosting site? I can’t seem to upload them from my hard drive here. Though the pedal seems to work properly, it would be nice to be sure that any extraneous noise is at a minimum.
Mike