joule la150mkII- preamp

Also, maybe call Rich at signature sound. He's the guy that does my part of the repairs on those at this point. He'll know and likely be able to tell you what to use to clean them as well. 

To clean the knobs while on the unit, try a mild soap and water solution such as dishwashing liquid on a cloth. If this does not remove the "dirt", it is probably because some of the thin plating has worn off the knob from the oil on your fingers. Consider it "patina" and continue to enjoy the music.

Thank you so much guys, really appreciate all your help.

sy

Either 3% vinegar or h2o2. Apply then let soak a minute or so then clear with clean water/distilled or RO

yes , but to do that i need to remove the knobs and for some reason, they do not come off. . i am trying, but afraid i will break them