JMP vs JCM800 2203/4 differences

[bonano]

Are there any? I think the early JMP 2203/4 preamps did not have a cascading preamp section. But excluding these, are the master-volume models not pretty much the same amp? Yet the JCM800s seem to be more popular. I kinda like the look of the amp going across the width of the head cab of the 800s as opposed to the previous looks. I'm pretty sure the chassis of the JMP's were narrower too, which would locate the transformers closer to each other?

[greatmutah]

The 2203 was always a cascading preamp. The 2204 was not. The JMP version was a different animal. By the time the JCM800 versions came out the 2204 preamp was the same as the 2203, just at 50 watts. 2204 was a shorter chassis and that goes back to the JTM50s/JMP 1987s/1986s. 100 watt amps and the longer chassis since the JTM45/100s. That didn’t change. I think the 2203 was pretty much identical minus component quality over the years until they started making changes in the 800. Some of that was filtering amongst other things. The change from vertical inputs to horizontal signaled a bunch of changes. To my knowledge, the JCM800 2204 stayed identical even after this change.

[turbopablo]

A vertical input JMP is still the greatest amp I've ever played. It had everything going on. It sounded perfect.

[Guitarbilly]

The 2204 only had a non-cascading preamp for a very short period of time (January to September of 1976). Those amps did not sound great, so most of them have been converted to standard spec by now.

From late 76 on, they're all cascading and basically the same circuit.

As greatmutah correctly pointed out, when they switch to the horizontal inputs they changed the filtering of the 2203. But it would be very easy for a tech to change it to the vertical specs.
The 2204 never changed.