Having added a Mourquiet to my SII and clones to my S.E.X. amps I want to share an experience:
After several weeks of daily use, switching the course switch suddenly caused loud static and crackling making me fear for the lives of my little Fostex drivers. At a given setting it was just beautiful music, but in-between was painful.
Reasoning that it must be the switch itself, I cleaned the contacts with a couple of blasts of Caig Degreaser Wash and a foam swab and ta-da...it's all good.
I don't know where the contamination came from, just an FYI for other users.