Help with my Genz Shuttle 9.0 making a new noise

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?

 

Great!
I'm assuming the pre tube swap is an easy move. I'll try it in the next day or three.

 

nailed it. the seller had swapped in a Groove Tubes 12AX7R which must have gone bad. he included an Electro Harmonix AX127EHwith the purchase, which i must assume is stock. it solved the noise issue. it also gave me a bunch of clean headroom. i can't push the pre into overdrive now, but it is a very nice glassy clean. i think i like it better.

 

Might be. I don't know.

Looks like the EHX tube isn't the silver bullet. I'm still getting some low level scratchy static with each note. Time to PM agedhorse.

 

Agedhorse to the rescue. After the tube swap, I still had a little static noise. He pointed me right to the culprit and everything is functioning again.

Now I'm thinking about rolling some tubes through there...

 

aside from the bad tube, there was a connection point by the Master which had jiggled too much. i gave it a gentle push to tighten up the connection, and that seemed to do the trick.