Hey guys.. bought my Mashall AVT100 (used) a little over a year ago, and I suspect that its about 4 years old or so (my guess). I have started becoming more and more unsatisfied with the OD channels on this amp. And this not only because my ear for tone has been developing, because when I tried the same model amp new in a store last week, the distortion was much tighter and better than my loose-sounding, flappy, thin distortion.. Now I was thinking, maybe this has to do with the valve in the pre-amp section of my amp, could it be worn-out or something like that?

I know someone who changed the valve in his Marshall Valvestate 8100 (basically the predecessor of my AVT) to a mesa/boogie tube of some sort (cant remember which model) and the difference was quite noticable! So now Im thinking of doing the same. Would it be the solution to my seemingly deteriorating overdriven sounds?

Thanks in advance, please no flaming about AVTs/hybrid amps/other crap like that.. Yes, its not the best but its all Ive got at the moment, I will be buying an ENGL Screamer 50 when I get the $$ soon enough...
Maybe its just that your amp is unreliable and dying. The tube in hybrid amps do almost nothing so changing it shouldnt make a huge deal. Just get a new amp.
^ But when I play with an OD/Distortion pedal through the clean channel, nothing seems to be wrong?
yes, replace the tube to something else. it will solve your problem, but get a high quality one because you only have one tube so make it a good one, problaby the hotter the better. and dont let people jade your idea of hybrid amps because the tube(s) do color the sound quite a bit and most of them sound way better than ss amps.