Vacuum Tube preamp with my KRELL KAV 250a, a no no......WHY?

I was told that vacuum tube equipment was "old 1940's technology." And that tubes created conditions and extraneous signals  that could/would fry certain components within the amp.  Is that so? 

I don't have the knowledge and understanding of electrical theory to comment on this from a technical perspective, but I would say that if you scroll through tyhe pages of this particular forum (amps and preamps) you will come across a ton of threads about, or icluding, people running tube preamps with ss amps.  I suppose there may be some, but off hand I cannot remember anyone posting about the combination damaging the amp.  But, as I typed, there may be some, but I think far and few between.  I cannot comment from my own experience because I have been running tubed preamps in front of tubed amps.  

Didn't the tech that told you not to do that tell you why?

@erik_squires  , can you explain what happens that makes that "pop" when a preamp is inadvertantly turned off before the amp?

Actually, OP, after reading @erik_squires  reply, I do now remember someone posting about losing a pair of speakers due to what @americanradiance just described.  That must be what your tech was talking about.

Thanks, @erik_squires  ; I always appreciate the tid bits of knowledge that I get from you and @atmasphere  .

@judsauce , well, we’ve got the long weekend coming up, so maybe that is having an effect on whose there to answer the phone. We’ll hope so anyway. Maybe if you give them a call on Tuesday you will get through. Have you got your eye on a pre that you are thinking you better get crap or get off the pot on? If so, I do know the feeling.