Hi Everyone,
I think we all have a bit of an idea how a guitar works, so I thought that I would start a thread about how a Valve Guitar amp works, I'm going to try and keep it relatively simple to understand, but I'll have to include a simple scientific principle which I think should help.
Here's the simple Scientific principle:
Like charges repel, un-like charges attract.
Okay, so, when we discuss how a Valve Guitar amp works, we need to first discuss how a Valve works, a Valve is an Electronic device which is used to control the flow of Electrons in an Electronic circuit, so what is an Electron?, an Electron is a very small atomic particle which has a Negative charge, in a basic atom, such as a Hydrogen atom, there is one Electron orbiting a nucleus made up of one Proton, a Proton is a very small atomic particle like an Electron but it has a Positive charge, so it attracts the Electron to it because the charges are un-like.
Back in around the late 1800's, Thomas Alva Edison, an American inventor, was trying to find a way to stop his recently invented Incandescent lamps from developing a black film on the insides of the glass envelope, incandescent lamps had an electrode called a Filament which glowed brightly when an electrical current was passed through it, Edison tried introducing a thin metal plate into the glass envelopes in an attempt to stop the blackening, and it was while he was doing some experiments that he noticed an interesting phenomenon, when the plate was made Negative, he noticed that nothing happened, but, when the plate was made Positive, he observed a small current-flow, this discovery led to the invention of the very first Electronic device, called a Diode (two-electrode), this new Electronic device was put to use in a device called a Radio, in 1907, Lee De Forest, another American inventor, created a new Electronic device, called a Triode (three-electrode), by placing a third electrode in between the filament and the metal plate in the glass envelope, Lee De Forest found that he could control the flow of current from the filament to the plate by applying a Negative-charge to the third electrode which he called a Grid (it was literally a grid of fine wire), he found that his new device, the Triode, could amplify, or make louder, weak signals, so it ended up being used in the early Valve Radios from the 1920's onwards, right up until the invention of a device called a Transistor in the mid 40's.
As it turns out, the Electron Valve proved to be a good device for making guitars louder, most guitarists these days seem to like the sound they get from a good Valve amplifier, although there are also some that like the sound of Solid-State amps too.
Anyway, going back to how a Valve Guitar amp works, when an electrical-current is passed through the filament, the filament heats up and glows a dull-orange colour, but something else also happens, the Electrons in the filament boil-off the surface (this process is called Thermionic Emission) much like how water-vapour boils off water when it's heated, you might have noticed this happening while making a hot cup of tea or coffee on a cold day, now because the plate is held at a high positive-charge, the Electrons (negatively charged) are attracted to the plate and a current flows, but if a negative charge is put on the grid, this repels the Electrons back to the filament, effectively stopping the current-flow.
I'll be continuing the discussion tomorrow, might also post some pics, so stay tuned
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