Re: marshall JCM800 2203/04, JCM900 mk 6l6, or JCM2000 DSL?
I've seen that schematic before, and think it's a very early circut, from around 1975. I have a copy of a 2203 schematic dated Nov 1976 that is as the JCM 800 schematics. However, the 50 watt MV circut from that early period is still like that lower gain version in the schematics. The Schematic may not match how the amp's were actually wired either. I'm not sure when exactly the 50 watt Master Volumes became like the 100 watt Master Volumes, and the later JCM 800's Master Volumes, but I'm pretty sure it was prior to introduction of the JCM800 models.
When the JCM800 came out in 1981 the changes were cosmetic, but the guts and the tone remained the same. Rose Morris (distributors) held a large inventory of JMP Marshalls, and Marshall had just terminated their contract with Rose Morris. Marshall came out with the JCM800 look, and that made the RM inventory obsolete. Eveybody wanted to buy the newer JCM800 looking amps through Marshall's new distribution network instead of the older looking RM inventory. It actually kept Marshall in bussiness at the time.
All 2204's that I've seen are electronically about the same regardless, if it's got the JMP or the JCM800 look. JCM800 is really a look, not a specific sound.
The real gainy JCM800's that people associate with 80's metal are probably the 2205/2210 JCM800 models, not the 2204 JCM800 models. Those have comparitively a lot of distortion at any volume. You usually have to use an overdrive/distortion device on an unmodded 2203/2204, to do metal at a reasonable volume.
50 watts of pure Rock N' Roll tone.:smokin:
