The cool sound of tubes

Although solid-state technology overwhelmingly dominates today's world of electronics, vacuum tubes are holding out in two small but vibrant areas - the microwave technology and the reproduction of music. Of these two, the latter is a more complicated area which stems from the fact that music is played to be heard by people, whose nonlinear ear-brain hearing systems are far from fully understood. Since no one know exactly how to model the human auditory system, no one knows exactly what engineering measurement are appropriate in evaluating the performance of an audio equipment. The importance and applications of the vacuum tubes in music are discussed.