>> no heat.
> Studer capstan motor drive amplifier that just roasted a hole in its circuit board!
Any power system can be made to overheat. Linear power amps are pretty sure to run hot. One small advantage of tubes is: between heater power and very poor conduction, they run hot at best and not much hotter when abused. Transistors need no (extra) heat to get started, and will happily eat all the power they can suck until they soften and quit or burst.
> Tubes use heat to make electrons to go thru them. - Transistors take 3 pieces of sand, glue them together, and a small signal going into the middle piece of sand makes a bigger signal flow thru the outside pieces.
It is hard to make electrons move from metal to vacuum. Heat is one way to make them move. The threshold temperature for a small usable flow is far above room temperature.
I think conventional transistor action also depends on heat. But if you glue that de-oxified sand together tight enough, the threshold temperature is far below room temperature. Ambient thermal energy plus a small voltage will flow big current. So there is heat needed, but anyplace you want to use a transistor probably has ample heat laying around.
Like: to get a steam engine started, you have to raise the temperature of some key parts to 100 deg C. To start a car engine on natural gasoline, the engine can be at 0 deg C or less (much less with refined gasoline blended for winter use).
> lesson on transistors
Travelers in St Louis want to go to San Francisco to work. There is an infinite supply of them. They can't cross by themselves. They need a Guide. One Guide can escort many Travelers.
The travelers stand in a place called "emitter". When Guides run out of money and are thrown out of the bar, they go to a place called "base", which is next to "emitter". Each Guide grabs 20 to 200 travelers and escorts them from Emitter to Collector, in San Fransisco.
The number of travelers who pass from Emitter to Collector is limited by the number of Guides you put in the Base. You can have a thin trickle or a massive flood of travelers.
The work done (pay to the guides) is the distance (2,345 miles, or 40 volts) times the number of travelers (or Amps). Obviously you could imagine a lower-pay low-power situation where Guides only escorted Travelers through, say, a small museum instead of across a great desert.
One monster flaw with this analogy: the Guides actually don't go to San Francisco, they only go Base to Emitter. And if you take that direction as given (it is ambivalent) then the travelers must go Collector to Base. The Guides take a short-cut and still manage to escort a large number of Travelers across a long distance.
And if that don't confuse you....