Hi, I am new to tube amps, and I have a Peavey Vypyr 120W All tube 2x12 Combo. I have two guitars, a Schecter C-1 hellraiser and a schecter C-1 classic. I've had it since the summer and i play it a few times a week for a couple hours. I mostly play metalcore.

recently I noticed 2 things about my amp. first is when I am playing on the 6505 setting or any heavy distortion setting for that matter, when I am playing high notes, the note will crack out after a few seconds if i hold it. I am assuming this is just the tubes and I need to change them. I've never changed tubes, how do I go about this? I know I need 6l6GCs and that JJ is a good brand, but is there any special kind of subtubes I need or anything special I need to do besides just plug them in?

the second thing I have noticed is something I just noticed today. I was playing around with the sounds and I went to a preset that came with the amp which was very soft, deep and lots of reverb. was playing my classic on it and I noticed a buzzing sound in the amp. It wasn't coming from the speakers, but from the back of the amp. It did not sound like it was coming form a tube, but rather the electrical box on top. It seemed to happen when I played very low notes, and wouldn't even happen if I put the volume at 2 or 3. any idea what this could be? is it something that probably needs to be fixed?

i doubt you need to change your tubes, you don't use your amp enough to need trube replacements at the moment, since you're hearing a rattle it might be wise taking it to a tech and get them to look at both problems
Alright I'm gunna bring it in to a local store. Thanks for the advice, even though i prolly woulda ended up doin it anyways lol.