Lovely piece about Jim Marshall by William Weir in The Atlantic.

When Jim Marshall designed his first amplifier in 1962, he used the 12AX7 vacuum tube, a seemingly slight deviation from the 12AY7 tubes of the popular Fender amps—because Marshall couldn’t find any in Britain at the time. This accident of geography meant that customers of his music store suddenly had a little more crunch in their guitar sound. In rock and roll—a genre forever entwined with technology—a mere vacuum tube begat a major shift in the music’s history.

Marshall, who died last week at 88, also had the fortune of having a 20-year-old Pete Townshend for a customer. Townshend told Marshall he wanted to hear himself over The Who’s audience and rhythm section. Thus was born the first 100-watt amp. Add to that two cabinets, each bearing four speakers—together, the components came to be known as the Marshall stack—and Marshall secured himself a permanent spot on any history-of-loudness timeline.

Loudness is strictly a psychological phenomenon referring to how the brain perceives the strength of a sound. But exactly why loudness appeals to so many of us is still a mystery. In his book, Your Brain on Music, neuroscientist Daniel Levitin suggests that very loud music saturates the auditory system, causing neurons to fire at maximum rates. Studies have shown that louder music causes us to shop more and work out more enthusiastically.