Tubes and their problems

I agree that microphonic tubes do not indicate failure but in fact I have used these tubes with great success, some of which sound pretty darn good. If they are too microphonic you can tame them a bit with tube dampers.

Does anyone know for sure what a tube exhibits before it dies. Maybe that can vary from one piece of gear to another. In my case the tubes in a preamp slowly lost gain and the gain would suddenly drop. I have heard that tubes in power amps can go out with a big bang and would require more frequent testing to ensure safety.

Atmasphere, thank you for your in depth answer. I was hoping that you could explain arc-over and its cause.

Bifwynne, of course, let us pray!

Daveyf, lets hope the bad tubes if any are in the preamp. I think you have some concerns but more importantly you are picking up a station I've never heard of.