Every forum I have ever read and anyone I have ever talked to says the circuit for the early JCM & JMP 2204's are the same except for the power trannies where the JCM's have a higher output voltage as compared to the JMP's. This 2x12” combo reissue has the legendary deep blues tone created by the GZ34 valve rectifier, similar to the JTM45. stm_aix("p0i25","p0i9",[0,"Home Page","","",-1,-1,0,"https://www.amprepairparts.com/index.htm"]); I borrowed my "History of Marshall" book to my brother but I'm thinking the 2104 was simply the combo version of a JMP 2204. Marshall manuals | You will find on this page the manuals and instructions for use for musical instruments, Marshall PA Equipment, studio, lighting and sound equipment. Posts: 17135 Joined: Wed Aug 01, 2007 3:02 am ... ↳ Marshall JMD1 ↳ Marshall JMP ↳ Marshall JTM ↳ Marshall JVM ↳ Marshall MA ↳ Marshall Origin ↳ Marshall Signature Series ↳ Marshall SL-5 $250.00. Here you will find our collection of Marshall schematics. The Rat is one of the earliest distortion pedals, arriving on the market in 1978. El Jefe. I have big problems with this terrible Popping sound then I turn it on and off.. stm_aix("p0i50","p0i9",[0,"Tube Accessories","","",-1,-1,0,"https://www.amprepairparts.com/tubeaccess.htm"]); Some people might doubt that, but after 20+ years of playing guitar, I am convinced this is the most versatile pre-amp in the business. The footswitch is hard-wired to patches 1, 2, 3, and 4, but it is simple to use the MIDI mapping and assign them to any other patch. "}})});