I called SWR about a vibration coming from the control panel on top. I noticed, esp. when hitting low notes, that I would get a rattling sound. If I applied pressue to the input jacks (head phone, etc.), then the vibration would stop. SWR explained that this is kind of a known glitch that the SWR WM10 at one time had. There is no wall inside the little cab separting the controls and interal chamber, so air can escape through the holes. Poor design? Maybe, but at least SWR is sending me some plugs for the unused input jacks which I"m told will fix the problem. I guess they had plugs for the WM10 problem when it was around.