I have a 2005 peavey 6505+ that when switched off of standby, it makes a sound I can only describe as white noise as well as a piercing high pitched squeal. It’ll happen sometimes when I turn it on and other times it happens 15-20 minutes into playing ( usually around 2 on the post gain).
It’ll will make this noise with nothing connected to the head other than the cabinet and the only knobs that affect the noise are the resonance and presence- turning the presence all the way down takes the high pitched squeal away but the white noise stays. I took it to my local tech and he found nothing wrong with it but a bad pre amp tube. A few months later the noises returned and are frequent than ever. Going to take it back to the tech this weekend and see if there’s anything else we can do - but I am hoping someone on here might have an idea of what might be going on
Thanks