#1
I have no replacement valves at the moment and my amp has two preamp and two power amp valves in. Can I just take these out and turn it on or is that something that would blow the thing up...

#2
People recommend you change them all at the same time, but you could remove the preamp ones first as I'd imagine that's safer.
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#3
Quote by MacMan2001
People recommend you change them all at the same time, but you could remove the preamp ones first as I'd imagine that's safer.

Do you know if i could remove say one of the preamp valves and turn it on to see if the rattle is still there? Or is that not a good thing to be doing?
#4
I vaguely recall hearing something about (gently) tapping the tubes to check for microphonic properties. The one that is microphonic, will obviously have a loud, distinctive bell-type sound. Check/read up on this before you try though...
#6
power amp tubes rarely go microphonic the same way that preamp tubes do.

also, the pencil tapping test is not really that accurate. Tap the first tube of any amp and you'll hear the tap through the speaker, they're all microphonic to a degree, you just don't want them to be microphonic to the point where it's bothersome. The best way to really see if a preamp tube has gone bad is to keep a good one on hand and swap it out of each position. Preamp tubes are cathode biased so you don't need to worry about biasing, just swap and listen.
Last edited by al112987 at Sep 10, 2009,