software

Im thinking about getting a 1979 Marshall JMP master model head but I read somewhere that they had the same circuits as the early JCM800s which I dont want. Does anyone know if thats true and if it is what years have the same circuits as the JCM800s? Thanks.

all the older Marshall stuff carried over...the early Metal Fronts were the same as a Plexi and the early JCM 800 were the same as the later Metal front MV's and the list goes on...also keep in mine Marshall's have always been somewhat inconsistant...they used whatever parts were less costly and there were lots of minor changes to the circuts that were never mentioned in books...

What are you looking for exactally?

I want a JMP mastermodel head that doesnt have the JCM800 circuit so what years would that be?

According to the Marshall book, the early JCM 800's were just cosmetic upgrades of the JMP MV amps, the post 1972 Marshalls are by far more agressive that the pre 1972's and the master volume amps came out in 1974, if I were you I'd grab any MV JMP amp I could find my book says that none of them would have the JCM 800 circut...

Do you think if it did have the JCM800 circuit than I could have it changed to the JMP circuit?

The early JCM800 were JMP in different clothes! The later 800's had diodes in the distortion channel, I assume this is the circuit you are refering to? If so you are correct in avoiding the later series 800's but I would go with the JMP!

So youre saying that all JMP master model heads were the same as the early JCM800s?


Originally Posted by guitarplayerSo youre saying that all JMP master model heads were the same as the early JCM800s?Thats correct...read post number 4...if you want the tone of a JMP MV amp get a post 74 MV, there was never a JMP amp that had t he circut if a JCM 800...

IIRC, the main change from JMP's to JCM 800's was more filtering in the 800's. But you look at the 2203/ 2004 circuit from JMP through JCM 800 through today's reissues and they are all virtually the same circuit. But...different transformers, cap types, etc over the years will make a difference in the sound. Try before you buy.