The knob is loose, and I am not sure how to get the bugger off (no small screw in it and I can't access the inside except via the f hole). I tried pulling on it a bit, don't want to break it if that is not the best way to get at it. It doesn't feel like there is a loose nut (I can get a finger in there and turn the volume up), so I am not sure how to tighten it up. Rather annoying design! Anyone have one of these?