Old TVs, early supercomputers, and modern fancy sound equipment all use vacuum tubes. But why? What does a vacuum tube do?
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It acts as a kind of switch that can be turned on or off with a small electrical signal. (Same function as a transitor actually just takes up gobs of space in comparison)
The electrical signal can be much much weaker than the circuit you are actually turning on and off.
So let’s say I have a microphone. It can use a tiny bit of a special crystal to generate an electrical signal from sound waves. If I were to hook this up to a speaker you could barely hear it and it’s a very very small voltage(if it made it move at all)
What I can do is take that tiny signal and hook it up to the “exciter” post (the part that receives the on/off signal) of a vacuum tube and then have 120V (household plug voltage in Canada/USA) on the switched part. The speaker now can see the 120V being turned on and off at the same frequency that the microphone signal is being emmitted.
Lots of other uses for them but amplifying signals like this is one of the main ones
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