Practical solid state diodes and transistors have made glass valve technology nearly obsolete.
Nevertheless, valves survive largely because electric guitar players much prefer the sound of valve
amplifiers to the sound of transistor amplifiers. This paper discusses the introductory-level
physics behind that preference. Overdriving an amplifier adds harmonics to an input sound. While a
moderately overdriven valve amplifier produces strong even harmonics that enhance a sound, an
overdriven transistor amplifier creates strong odd harmonics that can cause dissonance. The
functioning of a triode valve explains its creation of even and odd harmonics. Music production
software enables the examination of both the wave shape and the harmonic content of amplified
sounds.