I agree with your other responses, I think this is not valid but I'm
not certain. I'd like to find out from an expert just to be certain.
Some consider me to be an expert... the idea that a tube preamp can do anything to a solid state amp in particular is a myth plain and simple. Coupling caps being old has nothing to do with it. Its just a myth and no matter who is trying to propagate it, its still a myth.
Solid state preamps have coupling caps too and are just as failure prone in this regard as a tube preamp.
Well the fact is that all sorts of things can cause amp-dangerous thumps! This is not a solid state/tubes thing, because solid state preamps can easily make thumps! This is why many solid state preamps often have output muting protection relays. Many tube preamps do as well. But a protection relay is just about guaranteed to mess with the sound, so many preamp designers expect the operator to have some common sense and follow the procedure below:
Its just a matter of being careful- when turning on the stereo, always turn on the preamp first and wait for it to stabilize. Then turn on the amp.
But my friend is a Dr., so I have to respect his professional even though I still regard it should be safe or little risk only.
Apparently this is an example of having a doctorate but still having no clue about what one is talking about. In this case his opinion is just that and its bunk.