Quote Originally Posted by SemiHollow
Like spudman said, the rattling could also be a microphonic tube

Thanks for the suggestions. My amp is a crate v50 with two GT 6L6 power tubes and 3 12AX7 WB preamp tubes. I got the amp used, but was told that the tubes were pretty new (they are not original).

I took off the springs off the power tubes as I thought that was what was buzzing, but the buzz is still there. But it is sort of hard to tell exactly where the buzzing is coming from.

So, I cranked up the gain then I lightly tapped on the preamp tubes with a chopstick and got a chiming noise out of one of them - almost a clean feedback note. I am guessing that this preamp tube is microphonic.

This is my first tube amp (always had line6 amps before) and my first tube issue. I am perfectly capable of swapping out a tube but I don't know anything about biasing etc.

Assuming that I should replace the preamp tubes, what should be my course of action? Do it myself, or is this something my local guitar shop should do for me? Also is the amp playable, or will it do permanent damage to keep using it?

Thanks

Rich