Nomad 45 slight hum related to output knob

[Sir Punk]

I recently got a Mesa 45 and this thing sounds fantastic, so many sounds out of it. Everything works just fine but I am just wondering about a hum I get when the output knob goes past 11. Is this normal?
First I had it plug through an outlet strip and I thought it was that. So I plugged it straight into the wall plug and that reduced it. It's the same across all channels and it increases slightly when I plug in the guitar cable.
It's only related to the output knob. Maybe I am just being too paranoid but I read a few threads about hum but none of them were only related to the output knob.

any ideas? Could it be a bad pre-amp tube, dirty AC, bad grounding? I will give mesa a call.

thanks

 

[Sir Punk]

so I think I found the culprit, the ground prong was finnicky and broken, I removed it and that solved the problem. Now I am replacing the whole cable, I already tried the new cable and the amp is silent now.

i am just concerned about this cable is not as big as the stock one.