Part 5/7:
A key aspect of vacuum tubes is their ability to modulate signals. For example, connecting a weak AC signal (such as from a guitar pickup) to the grid can alter the electron flow between the heater and the plate. Consequently, the output current becomes a stronger AC signal that mirrors the input—this is the essence of amplification.
Clarifying a Common Misconception
It’s important to note that the stronger output signal isn’t simply a boosted version of the weak input signal in the traditional sense. Instead, the weak input signal modulates the flow of electrons—controlling how many reach the plate—resulting in a larger, stronger AC signal at the output.
An Analogy: Modulating Water Flow
To better understand this process, consider an analogy: