I went through a ham radio phase in the late sixties, as a boy, built a few kit recievers and a transmitter, then moved on to bigger and better things, engines and motor bikes, then went through electronics training for the Marine Corps, in the mid seventies, had tube theory, but was told by instructors not to worry about it, we'd never see a tube out "in the fleet". I retired out of the Corps in '97, my last tour as Non-Commissioned Officer in Charge of the same exact electronics shop I had for my first duty station, right here in North Carolina, and when I left, we still had half the six hundred odd systems we maintained for communications and navigations were tube driven, with solid state pre-amps and the like. At the same time, my new techs, checking in to the shop, mostly had never seen a tube and were shocked. Our radar units were up in the three to six thousand volt range for their finals, that didn't so much hurt as laid you out and got you a visit to the hospital, and two or three days bedrest. I hit 1500 volts of dc/rf out of a transponder, and had a small hole blown in my finger, right down to the bone, took about a year to heal, and almost six months to even start healing.
Working with solid state is very nice and much less painful now, I don't need to go back to tubes or valves as you chaps like to call them, over the pond, although they were easier to troubleshoot, and almost impossible to blow up, unlike the touchy little transistors. Tube amplifiers still produce the warmest sound and are much prefered by the "real audiophile", or so I've been told.