Play It Loud: The Story of The Marshall Amplifier


Chief Journeyman
Sep 8, 2012

Thanks for starting the new Audio/Electronics Pioneers forum for me.

Here is my first posting:

Click on the box next to HD and watch the video full screen.

The following text was obtained from Wikipedia ( :

Jim Marshall thought he could produce a cheaper alternative to American-made guitar amplifiers, but as he had limited electrical-engineering experience he enlisted the help of his shop repairman, Ken Bran, an EMI technician, Dudley Craven, and Ken Underwood. They most liked the sound of the 4x10" Fender Bassman and made several prototypes using the Fender Bassman amplifier as a model. The sixth prototype produced, in Jim's words, the "Marshall Sound".[SUP][6]

The original idea was talked about late one night in early 1963 in a Wimpy bar in Ealing in West London. The first six production units were assembled in the garden sheds of Ken Bran, Dudley Craven,and Ken Underwood in the same year, in Heston, Hanwell and Hayes, all in West London. They were almost copies of the Bassman circuit, with American military-surplus 5881 power valves, a relative of the 6L6. Few speakers were then able to handle more than 15 watts,[SUP][citation needed][/SUP] which meant that an amplifier approaching 50 watts had to use four speakers. For their Bassman, Fender used four Jensen speakers in the same cabinet as the amplifier, but Marshall chose to separate the amplifier from the speakers, and placed four 12-inch Celestion speakers in a separate closed-back cabinet instead of the four 10-inch Jensens in an open-back combo. Other crucial differences included the use of higher-gain ECC83 valves throughout the preamp, and the introduction of a capacitor/resistor filter after the volume control. These circuit changes gave the amp more gain so that it broke into overdrive sooner on the volume control than the Bassman, and boosted the treble frequencies. This new amplifier, tentatively called the "Mark II", was eventually named the "JTM 45", after Jim and his son Terry Marshall and the maximum wattage of the amplifier.

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