However, tubes are still used in several specialized applications such as guitar amplifiers (also called a valve amp outside the U.
The electrodes are attached to leads which pass through the envelope via an air tight seal.
On most tubes, the leads are designed to plug into a tube socket for easy replacement.
The next time you get into a Fender Bassman discussion you should narrow down exact which era, model and circuit you’re discussing. The tube charts are not very useful for determining the circuit model.
A lof of blackface Bassman amps with AA864 tube charts are actually AA165’s, and a lot of AA165 charts are glued into AB165 amps.
Vacuum tubes, or thermionic valves, are arrangements of electrodes in a vacuum within an insulating, temperature-resistant envelope.