OK. I have used both single coils and humbuckers and apart from the obvious sonic differences I have not experienced the distortion problem. I have read that the Worm can be noisy but that is a different issue. I have only used it with a Laney Cub 10 which is all tube I will plug into a transistor combo and check that out but it does seem strange !!!!!
I use the worm at the front of my fx chain – I have noticed some problems when it sits in the middle of a chain but distortion was not the issue. does the problem occur on all of the worm sounds ? Also what guitar are you using? single coils ? Humbuckers?