yea so i know someone just posted this for themselves...but i actually have the same question...

i need new tubes for my peavey xxx...its been almost 2 years and i havent changed em. and im getting a slight feedback-ish hum from my amp lately. brian says its the tubes. i dunno. what should i do?

Ya your tubes have probably gone microphonic.....2 years of moderate use is probably enough to do it....Id say change em out, if you have the money.
How many tubes do those things have?
I know my amp has 12 or 14 tubes in total, so its expensive to trade em out.

definitely tubes, with regular use you should have your amp re-tubed and biased every year. if you play loud. it will fuck with your sound (volume + EQ) if you don't.
if you're broke, replace the preamp tubes. you don't need to re-bias the amp if you replace those.

Whatever you do, don't buy the tubes that were originally in it (groove tubes)

Try some JJ bottles.

if you buy new bottles offline from american musical or soemthing, you can get monthly payment plans with no interest. it's more affordable than dumping 300$ on new tubes.

A 2 year old could rebias an XXX. You can figure it out.

yeah, the tubes have definetly gone microphonic. like niccolai said, get some JJs. I put a set in my 5150 and it was like night and day. i went through http://eurotubes.com for mine, bob is the man as far as this stuff is concerned. he has high gain tube kits that'll make the thing scream, not to mention his prices are the best on the net (seriously). A retube kit cost me barely over 100 bucks, which is dirt cheap.

Wow that IS cheap.

thanks doods

ahh, the word is out about eurotubes....