1966 Marshall JTM45 MKII
Contact for all details!
The Marshall JTM45, based on the 1950's Fender Bassman, is the first guitar amplifier made by Marshall and possibly one of the most famous amplifiers around as it launched British Blues/Rock in the '60's.
It was first built in 1963 in an all-aluminum chassis by Ken Bran, Dudley Craven and Ken Underwood. Because of its power, Marshall decided early on to build it as a head with a separate 4×12 cabinet with Celestion speakers. Early versions had used 6L6 or 5881 tubes (a US version of the 6L6 in the output stage, later models used KT66 (from 1964), EL34 (from 1966) and ECC83/12AX7 valves in the pre-amplification stage. Dudley was responsible for the changes from the Fender to what is now known as the JTM45.
Significant differences between the Bassman and the JTM include the all-aluminum chassis, a 12AX7 valve as the first in the chain (the Bassman has a 12AY7), the 4x12 Celestion speakers with a closed cabinet (compared to open-backed 4x10 Jensen speakers), and a modified negative feedback circuit which affects the harmonics produced by the amplifier. As Ken Bran later said, "The JTM also had different harmonic content, and this was due to the large amount of feedback that Dudley Craven had given it."
By the mid '60s, the JTM45 had become so popular that it began to supplant the ubiquitous VOX amps, even their AC50, though it was just as powerful.
The JTM 45 became the basis for many subsequent Marshalls, most notably the Marshall 1962 combo, later referred to as the "Bluesbreaker" due to its use by Eric Clapton with John Mayall's Bluesbreakers.