I am a Car Audio Electronics Tech, well, at least I was. Then along came the time for kidney transplant #2. I have also fixed just about everything else, including a paint shaker circuit board for the local Ace Hardware, and a special medical device brought in by a Highway Patrol trooper, (for his daughter's serious asthma) "I took that one real serious", etc. I've got repair tickets stacked to the cieling. With a 98% success rate. However, I came into the game, long after the tube stuff, and I never saw any of it. However, An associate of mine did, and he is a magician on tube equipment. I may have to talk with him. He was always talking about the industial Western Electric amps they used in theaters. I wish I could find a good tube amp to borrow around here. I'm interested...