History of the

JMP 2203 & 2204

Posted: 18th May 2023

We sat down with former design engineer Steve Dawson and product specialist Steve Smith for this Live for Music article to learn more about the all-valve JMP 2203 and 2204, 100-watt and 50-watt two-input Master Volume amplifiers.

Read time: 2 minutes


The JMP was created to keep up with the increasing demand for amplifiers with the ability to produce distortion and sustain at low volume levels for studio or home use. To create these amps, we took the base of the standard model 1959 100-watt and 1987 50-watt Lead amps and added two volume controls. The first control being a pre-amp gain control and the second a master volume control. Released in 1975 these amps, known as the JMP 2203 and 2204, became the first Marshall amplifiers to have a Master Volume control and the 2204 model quickly became one of Marshall’s most popular products.

A year after the release of the first Master Volume models a distributor at the time, Rose-Morris, requested for us to modernise and update the appearance of the amplifiers. The updates that followed were purely cosmetic and included a larger Marshall logo, thicker wood on the cabinet sides, plastic corners, and the levant was changed to elephant grain. Further updates included the toggle switches being removed and replaced with illuminated rocker switches and the ST1 internal circuit board was introduced. This circuit board changed the amps from being fully handwired to semi-handwired. Despite all these changes, the signal path remained untouched.


With two ECC83 preamp valves, four EL34 power valves and 1 balanced ECC83 for the phase inverter, the JMP 2203 and 2204 are single channel amps with one high and one low sensitivity input for varying clean and distorted tones. The low sensitivity input provides much cleaner lower gain sounds by bypassing a gain stage in the preamp, this makes it an ideal pedal platform. Whereas, the high sensitivity input provides much brighter, distorted tones. 

Hear it for yourself

Listen to Steve Smith and Steve Dawson play through the JMP 2203 and 2204 below in our From The Museum series on YouTube

From the museum takes a look back at original Marshall amps from our archives and discusses how these amps came to be. In this series you will be able to hear the amps for yourself, as product specialist Steve Smith demonstrates these iconic amps that have shaped Marshall Amplification into what it is now.