Hi,
Well one thing I found out for sure tonight is: using the HI OUTPUT on the MULTI circa DOUBLES the amount (level) of artifacts when the MXR CC is activated. I changed it round last night to try this different OUTPUT, and at the same time, hooked up the MXR. Bad idea because I should have eliminated each individually. But I just realized tonight that the OUTPUT was HI so I changed it back to LO, and the results were better.
I may try and make a dedicated recording tomorrow. The artifacts are ONLY in the UPPER (2’) register. And they sound almost pitch-like (ie high harmonics).
Best,
Paul