The Marshall story is one of small shops and big names. Jim Marshall himself was not a guitarist. In fact, Jim was a drummer, whose small shop in Hanwell, London, founded in 1962, sold drums, cymbals and accessories. According to legend (and Jim Marshall himself), guitarists Ritchie Blackmore (Deep Purple) and Pete Townshend (The Who), would often come into the store to request that Marshall make guitar amplifiers to their specifications.
With no expertise himself, Marshall hired three designers to work on new type of guitar amplifier. The team took their inspiration from the 4x10-inch Fender Bassman, the sound of which they all admired greatly. They made two specific changes, however, that came to define the Marshall look and sound. Firstly, they separated the amplifier from the speaker cabinet, creating the iconic Marshall 'stack'. Secondly, they used higher-gain components in the circuitry, which caused the amplifier to 'break up', or overdrive, at lower volumes and 'scream' in the high frequency range.
That amp became the JTM 45, and the same design principles that built it lead to other iconic models such as the Bluesbreaker, Plexi, JCM 800, and Silver Jubilee. The uncompromising power and overdriven precision of Marshall amplifiers has led them to find favour with legendary guitarists like Eric Clapton, Jimi Hendrix, Joe Satriani, John Frusciante, and Slash.