The triode does not amplify, it regulates
I'm working on explaining the triode. Aside from the transistor it was the greatest help for the telephone system in the 20th century. Amplifiers developed from triode research enabled nation-wide calling for the first time in the mid-teens. I am drowning in pages and pages of information. A reader named Dante, a real radio expert, is helping me. I know the few sentences below won't make sense to most people, but I did want to show you that I am indeed working on what I said I would. Check back in another day or two. You'll find these paragraphs added to and modified to make them less cryptic.
I've written that a triode amplifies but this is wrong. A triode based amplifier certainly does make an audio frequency signal louder. But it takes a collection of components, arranged on a carefully designed circuit board, and, yes, the triode, to make amplifying possible. Think of the triode, for now, as a volume control, not an amplifier. The triode's "arrangement of filaments," modifies or regulates a current, it does not amplify.
When heated to incandescence the cathode begins to emit electrons, which flow from the negatively charged cathode toward the positively charged plate. The grid, where the original signal is introduced or injected , controls the electron flow. The result is that a tiny voltage, carrying the original signal, varies a much higher voltage at the plate or anode.
In our circuit high voltage drives a speaker. The amplifying, or better put, the gain, occurs when the audio frequency signals, say our voice, impinges on the existing current at the anode. These current variations act on the loudspeaker which then replicates speech. To sum up, you have a small current that varies a larger current. The triode itself regulates or modifies current, it does not amplify.
I write too much here today, it's back to work on the original article.
The grid. In this diagram the metal spiral where the unamplified signal is introduced. Located between the cathode and plate, the grid controls electrons passing through it by means of a negative electrostatic field.
Heater: Produces electrons by thermionic emission. Current passed through a filament-like heater makes it glow, boiling electrons off its surface.
Cathode: cylindrical, metal element in close proximity to and enclosing the heater. Electrons penetrate it easily and emit from its surface.
Anode or Plate: solid, cylindrical, metal element with high, positive potential, surrounding grid and heater/cathode assemblies. It accelerates electrons toward it and collects them for the external circuit.