this post was submitted on 08 Mar 2024
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No problem. It’s nice to talk about this stuff. If you want the skinny on amplifiers:
There’s two parts: the volume control and the amplifier. The volume control sits in between the input and the amplifier circuit itself. The amplifier circuit can be thought of as a fixed multiplier of whatever signal goes in. If there’s x50 gain then it’ll make an input of 20 into 1000 arbitrary units(tm). An input of 2 would be made into an output if 100au and you choose between those two inputs or any number you like with the volume control, acting as an attenuator before the amplifier starts multiplying the signal.
To look a little closer, the amplifier takes a big dc voltage and modulates it based on the small input voltage. If it was a tube amplifier, all the dc voltage gets put on the plate of the tube, the input is sent to the grid (a literal grid of wire in between the plate and cathode) and electrons jump through the grid to the cathode in proportion to the grid current. If the grid current is a song, then the massive amounts of electrons gathered at the high voltage plate will jump across to the cathode in proportion to it and if an enterprising person were to put a transformer and speaker in between the cathode and their path to ground those electrons could be used to move it back and forth!
Of course, they only do that in a vacuum and when heated up, so all that takes place inside an evacuated glass tube with those parts crammed into it next to a light bulb filament to make them toasty.
Point is: you’re not even getting the same electrons!
Your solid state amplifiers are doing the same thing but with transistors instead of vacuum tubes. Feed the input into the base of the right kind of transistor and it’ll let more or less voltage move in the direction of its arrow.
You get a few of the input electrons with a transistor, but it’s mostly electrons from the big dc voltage.
Ahh ok, that makes more sense. I think I never saw the connection between a transistor and an amp until now. Using a small signal to modulate a different, larger signal. Or like a relay.