Vacuum tubes are the ultimate in simplicity! With a dozen or so passive components, a couple transformers, and some know-how, you have an amazing sounding amplifier!
Tubes are "perfectly imperfect" - which means they exhibit qualities that alter the sound in a way that's pleasing to the human ear. - This is called Harmonics. Solid state amps also generate harmonics, but not in the same way! Most solid state amps include circuitry designed to emulate that tube sound!
I've been repairing, refurbishing and creating tubes amps since 2019, and learning more every day. I create new guitar amps from old vintage AM radios, tube reel-to-reel players, or from scratch.