This is why rock musicians prefer valve amps

New Delhi: Scientists have thought of an answer as to why rock musicians prefer valve amps. This is because their rich, warm sound is more pleasant to the ears of so many rock musicians than cheaper transistors.

For many guitarists, the sound of an overdriven valve amp - think AC/DC's crunchy Marshall rhythm tones or Carlos Santana's singing Mesa Boogie-fuelled leads - can not be beaten, researchers said.

David Keeports, a physics professor from Mills College, California in the US, looked at the science of valve amps to explain why their sound is 'better' to the ears of so many guitarists.

"Although solid state diodes and transistors are cheaper, more practical, and technologically more advanced than glass valves, valves survive because so many guitarists are exacting about their tone, and prefer the sound a valve amp gives them," Keeports said.

"At its most fundamental level, this is because a moderately overdriven valve amp produces strong even harmonics, which add a sweetening complexity to a sound. An overdriven transistor amp, on the other hand creates strong odd harmonics, which can cause dissonance," he said.

Keeports explored the physics of why even harmonics enrich a sound, and why the timbre of the sound from a valve amp changes when a guitar is played more loudly.

He ran a 200 hertz (Hz) sine wave - a pure wave with a single frequency - through a small Bugera hybrid amplifier, featuring a valve preamp and a solid state power amp.

(With PTI inputs)