I am wondering when do we need to change the tube inside our amp, i am using VOX AD50VT ? Where to change?

I don't really think you need to change the tubes in that Vox. But i may be wrong, don't quote me on that.

It has a pre amp tube inside ? No need to change? I thought the tube should run off after 1 year or maybe more?

If everything works alright there's no need to change it.
Pre-amp tubes should last a lifetime anyway since it's running very conservatively within its limits.

haha thing is, the preamp tube is in the poweramp section

=p

until you cant stand your tone anymore.

But for 1 12AX7 tube, it wouldn't hurt to change it every year or 2 depending on how often you play. The sound will get muddier when the tubes are old. That's how to know when to change them. Like my previous poweramp sounded so crappy but i couldnt afford to change all 8 EL34s so i just sold it off And bought myself another when i had cash again

8 tubes... is it a push/pull amp?
Can't you just bias them when it sounds muddy?

not when all the tubes are dead. It's a stereo amp and both channels were completely mud

Hmm...12AX7 tube cost how much one ? And , can i change it myself? I am in kedah now i dun think there is any shop can change for me..

ranging anywhere from RM40-100++. Depends on brand and build.
I think you should be able to change it yourself. It's like changing a fuse. Unplug old one and plug in new one. But i have seen some older tube amps where the feet are soldered. But i assume the ADs use the socket mount.

i remember seeing sovtek 12ax7 for around RM70++ at an audiofile hifi shop.

Which brand is the most recommended one ?

Hijack the topic for a bit (Mod privilege.... ).....

Anybody knows how much and where to get 6550 Power Tubes? Might pass them to Nik of Ceria Tone when he builds my JCM800

When you start to think "Hm, the sound was much better when I first got my amp". Plug in a new one, if it doesn't change much, you were probably just imagining things, but hey, then you still got one spare tube

@btrix
try octave electronics
i forgot their website

octave-electronics.com i think
if it doesn't work don't shoot me =p

they carry lots of tubes, i think =p

@threadstarter
y don't you give JJ 12ax7 tubes a try?
i heard they have higher gain, warmer and less microphonics compared to the ehx tube we have stock =p