Weird amp noise, trebley..

[jvhc]

Hey

 

I've got a Peavey Classic 30 and after about a minute, it starts making this high pitched ringing noise, like feedback. Even when I play over it, it's quite prominent.

 

It's not the cables, guitar or pedals - I unplugged everything and it still made the noise. It still does it when the volume is on 0.

 

However, it does get quieter as I turn down the treble knob. I dunno if that's just because turning down the treble cuts down the treble range and so it pretty much eq's it out..? It isn't really really high pitched, but it's quite high.

 

With the treble boost switch on it gets louder. Basically, the only thing that affects it is the treble knob and treble boost switch. With everything on 0 it doesn't make the noise, but if treble gets turned up, the noise comes back.

 

Anyone know why it's making the noise and how to get rid of it?

 

Thanks alot.

[Herald of Light]

Try changing the tubes.

[jvhc]

Wow, you got it in one!

 

I had one spare tube - swapped it with the first tube on there and it worked!

 

Also, there was no loudish bang noise when I turned the amp off, like there was before I switched tubes.

 

Thanks alot