Hello, just purchased this amp, play almost everyday and love it. When I first got it (playing for hours) I noticed there was a crackling/scratchy... almost like a loose connection sound from the amp, I played around with the cord and it didnt happen again until tonight, about 2 months later. This time it didnt just go away so here are my observations:

I was on full power, maybe 2 on volum, on the clean channle with gain. It seemed fine on e, B, G but on D is where it happened, didnt matter what fret and it seemed to do it on the A and E as well but not as much, I switched channels it did the same, I went into standby and switched cables, same thing, I plugged the guitar in another amp and the issue did not happen, I plugged the guitar back in to the marshal, the crackle was still there. I turned the amp off, put it in half power, turned it back on and no crackle. I turned the amp off, did a few things around the house. came back, put the amp back to 40W, turn it on and it is fine.

Thinking it happens if it gets warm? I have never had a tube amp... so im not sure what signs to look for with regards to a tube going bad... I'm not sure if originally leaving it at 40W and restarting it if it would have been fine. I will try and recreate and see what happens. Any thoughts?

UPDATING:

The foot switch made no difference. I'll move it to another room tonight. I have included a recording if anyone wants to hear it. In the recording you here the noise, I hit the B string 3rd fret... and it goes away, i then hit the D string 12 fret and you hear it come back.

https://drive.google.com/file/d/0B0GN6N50JSBpbTdwZUFWYVVTOU1TMFdfODdFRmdSQkxEcjNB/view?usp=sharing