Marshall's 40th Anniversary JTM45/100 head reissue. Photo courtesy of Marshall Amplification.

It’s the stuff of rock legend: In the summer of 1965, Pete Townshend asked Jim Marshall to build an amp even larger and louder than Marshall’s current JTM45 model. Marshall delivered with model 1959, sometimes called the JTM45/100 due to the fact that early models featured the JTM45’s distinctive front-panel. It featured four output tubes in place of the JTM45’s two tubes. The Who first used the new model—with a colossal 8x12 cabinet—sometime around November 12, 1965. Finally, the band had amplifiers loud enough to compete with Keith Moon’s explosive drumming.

But there’s more to the story of the first 100-watt stack. Jim Marshall (who passed away in April 2012 at the age of 88) and his visionary colleagues, Ken Bran and Dudley Craven, had to surmount countless design hurdles and battle the technical limitations of available components. It’s a tale of ingenuity, dogged determination, and sheer lust for power.

But to tell it, we must back up a few years.

The Genesis of Crunch
It was probably just a matter of time before someone realized that rock ’n’ roll needed another voice for its guitars in addition to clean Fender amplifier tone. But who would have thought that someone would be a drummer? A drum teacher, Marshall began selling drums on July 7, 1960, at his new shop at 76 Uxbridge Road in Hanwell, a town in the London borough of Ealing. “All the drummers used to bring their groups in with them, which is how I got to meet guitarists like Pete Townshend and Ritchie Blackmore,” Jim later said. “They kept pestering me to stock guitars and amps, so I decided to give it a go.” As a result, Jim expanded to electric guitars, basses, and amplifiers—a wise move due to the booming rock ’n’ roll market.

In 1965 Pete Townshend and John Entwistle of the Who were trying any amp that might be heard over Keith Moon’s drums.

In 1962, Jim hired Ken Bran as his repair engineer. Marshall’s shop was selling Fender and Selmer amplifiers, but Fenders were expensive in the UK, and Selmers broke down too often. In conversations with players who came to his shop, Jim realized many were searching for a sound they couldn’t quite get from amps available at the time. “Listening to what they were saying gave me a very good idea of what they wanted,” Jim recalled. “So, I decided to put together a small team to build a valve amplified with the specific sound the lads were after.” As a result, Marshall and Bran discussed producing their own amplifier. Bran told Marshall that he was comfortable doing repairs, but could not create a complete circuit. He recommended Dudley Craven, an electronics apprentice then working at EMI Electronics. Craven, 18, was known as the “Whiz Kid” because of his youth and skill with electronics. He jumped at the challenge of realizing Marshall’s vision of a rock ’n’ roll guitar amp. Ken Flegg also joined the team as an engineer who assembled the components on tag boards.

Marshall's 40th Anniversary JTM45/100 head and 4x12 cab reissues. Photos courtesy of Marshall Amplification.

Creating the First Marshall Amplifier
In the fall of 1962 Craven was living at 202C Uxbridge Road while working for Marshall. Behind the house was the tiny ham radio shack where Craven broadcast as “G3PUN.” Here Craven conducted most of the original testing of the JTM45, Marshall’s first amplifier. Friends would sometimes find Craven asleep at the workbench, exhausted from trying to keep up with amplifier orders.

JTM45 prototyping began in September 1962. In those early days Marshall would fabricate the aluminum chassis, preparing it for component mounting. Bran would obtain and install the bolt-on components, at which point Craven, the chief designing engineer, would take over the build, installing the circuit board, wiring everything, installing tubes, and setting the bias. The team produced about one amplifier per week. When a prototype was completed, Marshall would ask Pete Townshend or Ritchie Blackmore to demo the amplifier at his shop. After five prototypes, a sixth was chosen to become the production model. “As soon as I heard it I said, ‘that’s it – that’s the Marshall sound.’” Jim later remembered. “It was the sound I could hear in my head based on what the boys told me they were looking for.” This unit would become known as the “#1 amp.” Its circuitry essentially mimicked that of the 5F6-A Fender Bassman amp, though with some subtle departures that resulted in different gain, loading, brightness, and harmonic content.

By June 1964 the first Marshall factory had opened on Silverdale Road in Hayes. The 5,000 square foot facility was staffed by 15 employees who produced about 20 amps a week. Celebrities like Brian Poole & the Tremeloes and the Who would drop by, creating an exciting work environment.

Enter the Who
In 1965 Pete Townshend and John Entwistle of the Who were trying any amp that might be heard over Keith Moon’s drums. They briefly used Vox amplifiers, though they were ultimately deemed unsatisfactory.

At the time most amplifier components were rated up to 450 volts of direct current (VDC) and would fail at higher voltages. Said Townshend in an August 1996 interview with (now-defunct) British magazine Guitar, “Fender didn’t go any further with it after the late ’50s. The theory was if you went any further, literally all the other components would melt because they’d been designed for much lower voltages.” Marshall built a 50-watt amplifier known as model 1987 for Townshend, but it wasn’t loud enough. “I went back and said, ‘No, I want it even louder, even bigger,’” he told Guitar.