Hey, I'm lookin for some advice. I have a peavey valveking 212, and whenever i try use my clean channel it lets out a high pitch squeal that gets louder quickly. My lead channel, however, works fine. any help would be appreciated, thanks.
Bad preamp tube? Easiest way to find this out is to switch your preamp tubes around and see if the problem changes channels.
Hi, I'm Peter
for sure a bad tube eh, i just had em checked out a week ago. thanks tho i'll try that.
This may sound really rare and stupid, but I have a backlit keyboard that when the light's on and I'm playing guitar I get the high pitched squeal.

If you by any possible chance have a backlit keyboard then turn it off...