Hey I was just wanting to know, for something like a guitar amplifyer what is the inputted signal connected to on the valve (cathode, anode, filament or grid) and also what the outputed signal is connected to.
Think of an emitter (cathode) and a receptor (anode). This is a simple diode. If you put a grid between them (to make a simple triode) and hit it with an input signal, you can suppress or allow the flow of electrons from the cathode to the anode. Thus, a small input signal can be made to produce large variations in the output signal. The filament is a simple resistive heater that is used to warm to cathode so that electrons can be driven off it more easily.