More about tubes
Vacuum tubes are amplification devices. You have to amplify the signal coming
from a guitar or CD player in order to play it through a speaker. A basic power
tube works like a valve by using a metal grid to control the flow of
power going between 2 plates, the cathode and plate(anode). The power goes from
cathode to anode, and the power from the anode is what drives the speaker. The
power from a cathode comes from electrons given off when the cathode is heated.
Usually there’s a little heater right next to the cathode, or the cathode can
be the heater itself. If you put a positive (opposite) charge on the anode, the
electrons are attracted to it. But the electrons won’t become music until you
attach a signal source to the grid, which will control the flow of electrons to
the anode(plate) depending on the music signal. You then have a “more power”
version of the music signal coming off the anode. Since a few hundred volts are
needed to attract those electrons, you need a transformer to convert the high
voltage to something a speaker can handle, like 10 volts or so.
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