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PS: a vacuum tube, controls electrons going from a hot metal to a metal plate. The flow of electrons is a current, like water from a faucet. The current is controlled by the electrons going through a grid. a grid is wires strung across the current-flow, which repel the electrons like magnets do. Just as you can control water by turning a faucet, you can control electric currents with a vacuum tube, by changing voltages on its grid. Old radios and TV's, very old computers, used vacuum tubes.
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One notable exception - Many of the best new production guitar and bass amps still use tubes. It's not a nostalgia thing, they often sound better and there is a market for the "tube sound" because solid state amps can't seem to reproduce it. I use both tube and solid state amplifiers. Many have tubes as pre-amps, there are also guitar pedals with tubes in them, same purpose. They warm up the sound before the post-gain power amplifier pushes the sound signal to the speakers. Bill