I've got a Genz Shuttle 9.0 which I bought used. It's done mainly lower volume work as a practice amp since I bought it, and it's been trouble free. It has had an occasional scratchy noise when turning some of the pots, but nothing major. I recently took it to a jam session and powered up my Barefaced Compact and Midget stack. It seemed find then. Though when I attempted to run just the Midget it did hit the limit light a few times, so I quickly stopped doing that. It seemed fine the rest of the night. Last night I fired my rig back up and with the power on and the mute switch engaged I got a loud crackling static noise through my cabs. I tried each cab individually, and I tried swapping speakon cables, but the crackling hiss was always there. Out of curiosity, I tried turning the dials. With the gain and master levels down, the sound went away, but came back as I turned up. I found turning the EQ knobs made the tone of the crackling change; sweeping the mids gave me a wah like effect. All of this was with the mute switch on. I tried the cabs with my Mess Buster and I had no issues. I think I've narrowed this down to being a Genz head issue. Does this sound familiar? Did I fry a component? Is this an issue with the pre tube? I do need to try swapping that since I do have another tube. Any other suggestions on what to look for and how to deal with this?