#1
i bought a used at-100 head, i have a new matching cab. its a great amp from what i heard, and i really love the tone. its works fine, but i know the tubes must be at least a year old. and they are ****ty chinease. also my tone breaks up at louder volumes and i know thats exactly what tubes DONT do. i know its a good amp, so can old bad tubes cause tone to break up at louder volume?
#2
It's supposed to break up at higher volumes, that's what tubes do. 1 year isn't very old and btw almost all current tubes are made in china or russia.
I don't give a shit if you listen to me or not
#3
Your tubes should still be fine. Manufacturing processes are much better these days so a tube can last quite a while. If you're after a change of tone however, new tubes can generally be the ticket. Head over to eurotubes and give them an email and see what they recommend.
AMP:
5150 combo
GSP1101 + Tech 21 PE60

GUITARS:
ESP LTD M-255 w/ SD Full Shred
Kramer Vanguard w/ JE-1000 active preamp
Douglas WF-150sn w/ GFS "Hot Lead" set

EFFECTS:
Bos SD-1 (boost)
AMT DT-2

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#4
jsut to clear things up they are like no name brand, really really bad quality.
#5
when you say break up, you mean distortion right, thats normal, the higher your amps cranked the more gain you`ll have

but if you think there a problem, send your amp into a music store and have them look at it, they can tell you in 2 seconds if it needs tubes