Vacuum tube

A vacuum tube is like a special kind of light bulb that doesn't have any air inside it. Instead it's completely empty, like a straw that you suck all the air out of.

When electricity flows through the tube, it heats up a special plate inside called the cathode. This makes tiny particles called electrons break away from the surface of the cathode and shoot out into the empty space inside the tube.

The electrons then crash into another special plate, called the anode or plate, at the other end of the tube. This makes more electrons break away from the anode and keep the flow of electricity going.

Vacuum tubes were used a long time ago in things like radios, computers, and TVs. They've been mostly replaced by newer technology like transistors and microchips, but some people still think they sound better for music and audio.