Anonymous asked: What is a tube?

good question, a  vacuum tube is used for many different applications in electronics. in a tube amplifier (to which i think you are referring) uses 3 different type of tube ..rectifier, which changes ac current to dc current, preamp tube, which takes a small input signal amplifies it to a specific gain ratio..and output tube…takes amid size signal and amplifies it to a set output wattage..(based on plate voltage and bias