Re: vox tubes
If a power tube goes down in a bad way, it can take some bits with it, and a HT fuse if you're lucky.
And, yes, inside are more than a single tube. A tech is best.
Your'e looking at 12ax7 and EL84 valves, and numbers depend on which Vox you have.
Oh, of course, you might have one of those AD amps with just the one little tube for the preamp. In that case, go get three various ones, and taste them to your liking. Theyre cheap.