Members Burstbucker Posted January 2, 2008 Members Share Posted January 2, 2008 I scored a 1983 JCM800 2204 last year and I was wondering what's the difference between this head and a 50W 1980 JMP MV head? I know that the JCM800 has an extra gain-stage in the circuit when using the High input, that wasn't the case with the 1980 JMP master volume amp was it? I think that this is the proper schematic for a 1980 JMP 50 watter:http://www.drtube.com/schematics/marshall/2204u.gif Also, were there different types of JMP heads in 1980, wasn't there the JMP MKII, are these all fairly similar? Was the 1980 JMP MKII head a master-volume head? I've seen MKII's with four holes and some with two holes, I'm trying to figure all this out, can somebody shed some light on this! Link to comment Share on other sites More sharing options...
Members Blackwater Posted January 2, 2008 Members Share Posted January 2, 2008 I have a JMP Super Bass from 1980 (4 holes) no MV, but I can jumper the two channels. I also have a 1980 Park (4 holer) w/ an added MV. I don't think the JMP master volume had the extra gain-stage. There were are few different types of JMP's in 1980 and like all marshall's each one sounds a little bit different. Link to comment Share on other sites More sharing options...
Members telephant Posted January 2, 2008 Members Share Posted January 2, 2008 The JMPs were: 1959/1987 = 100 and 50 watt Non Master Volume Amp (four inputs)2203/2204 = 100 and 50 watt Master Volume Amp (two inputs) They continued the 2203/2204 amps into the JCM 800 line... Also, they all said MK II on them. Link to comment Share on other sites More sharing options...
Members Burstbucker Posted January 2, 2008 Author Members Share Posted January 2, 2008 Thanks for that info! I'm kind of surprised that these JCM800 Marshalls are still priced so reasonably, I got my 50W head and 1960A Classic 4x12 cab with Celestion Greenbacks for $1200.00 and both pieces are in very condition too. I thought that that was a great bang for the buck. Link to comment Share on other sites More sharing options...
Members .homewrecker. Posted January 2, 2008 Members Share Posted January 2, 2008 my 79 JMP and the 1980 800's I've tried have all been very similar I think the difference you're going to find will be the same from amp to amp in the same model. Link to comment Share on other sites More sharing options...
Members Burstbucker Posted January 2, 2008 Author Members Share Posted January 2, 2008 So, you didn't find that the JCM800s had a lot more gain then your '79 JMP? The JCM800s at that time, were kind of like a hot-rodded Marshall with that extra added gain stage in the preamp section. It seems that Marshall was just keeping up with what players wanted at that time I guess, which was a hotter version of a standard Marshall of that era. Link to comment Share on other sites More sharing options...
Members clay_finley Posted January 2, 2008 Members Share Posted January 2, 2008 JCM800's come in non-master and master volume models (as per telephant above). The master volume models have cascaded gain stages (more gain). Link to comment Share on other sites More sharing options...
Members Burstbucker Posted January 2, 2008 Author Members Share Posted January 2, 2008 Oh wow, I never realised that early JCM800s were non master-volume amps, I just assumed that all JCM800s came with a MV. Interesting! Link to comment Share on other sites More sharing options...
Members clay_finley Posted January 2, 2008 Members Share Posted January 2, 2008 I scored a 1983 JCM800 2204 last year and I was wondering what's the difference between this head and a 50W 1980 JMP MV head? I know that the JCM800 has an extra gain-stage in the circuit when using the High input, that wasn't the case with the 1980 JMP master volume amp was it?I think that this is the proper schematic for a 1980 JMP 50 watter:http://www.drtube.com/schematics/marshall/2204u.gifAlso, were there different types of JMP heads in 1980, wasn't there the JMP MKII, are these all fairly similar? Was the 1980 JMP MKII head a master-volume head? I've seen MKII's with four holes and some with two holes, I'm trying to figure all this out, can somebody shed some light on this! That's the wrong schematic for a 1980 50watter. That's the 2204 transitional schematic that was made late 1975 thru 1976 (until they figured out that cascaded gain stages was much, much better). It doesn't have cascaded gain stages (only a master volume). Link to comment Share on other sites More sharing options...
Members clay_finley Posted January 2, 2008 Members Share Posted January 2, 2008 Oh wow, I never realised that early JCM800s were non master-volume amps, I just assumed that all JCM800s came with a MV. Interesting! You're not all the way there yet... non-master volume amps were made until 1981. master volume amps were made starting late 1975. They were making both from 75-81. (first as JMP then as JCM800) JCM800 is a marketing designation. Link to comment Share on other sites More sharing options...
Members .homewrecker. Posted January 2, 2008 Members Share Posted January 2, 2008 My JMP has a stock MV (no mods other than to accept EL34's) and the difference between the 800's and the JMP gain wise can be attributed to tubes most of the time my JMP has more gain and on occasion an 800 has more gain than the JMP. Link to comment Share on other sites More sharing options...
Members atrox Posted January 2, 2008 Members Share Posted January 2, 2008 You're not all the way there yet... non-master volume amps were made until 1981. master volume amps were made starting late 1975. They were making both from 75-81. (first as JMP then as JCM800) JCM800 is a marketing designation. They didn't stop making them. Only the JMP versions. There are plenty of early/mid 80's JCM 800 1959's out there (4 hole/non MV). Not as common, but not hard to find Link to comment Share on other sites More sharing options...
Members Sudds Posted January 2, 2008 Members Share Posted January 2, 2008 I thought the JCM 800's with more pre-amp gain are the 2210 (100watt) and 2205 (50watt) heads and whatever combo's were in that range.... Link to comment Share on other sites More sharing options...
Members Burstbucker Posted January 2, 2008 Author Members Share Posted January 2, 2008 The 2205 came along a few years after my 2204, I'm not sure that the 2205 has more gain but it does have two switchable channels and added reverb, while the 2204 was only single channel and no reverb. Link to comment Share on other sites More sharing options...
Members Sudds Posted January 2, 2008 Members Share Posted January 2, 2008 The 2205 came along a few years after my 2204, I'm not sure that the 2205 has more gain but it does have two switchable channels and added reverb, while the 2204 was only single channel and no reverb. Yes a 2210 does have more dirt/preamp gain compared to a 2203 (my bro has a 2210 and I have a 2203), but the 2203 with a boost in front sounds a bit better, more 'open' IMO. Link to comment Share on other sites More sharing options...
Members The Idiot Posted January 2, 2008 Members Share Posted January 2, 2008 They didn't stop making them. Only the JMP versions. There are plenty of early/mid 80's JCM 800 1959's out there (4 hole/non MV). Not as common, but not hard to find I have one and I love mine. Link to comment Share on other sites More sharing options...
Members telephant Posted January 2, 2008 Members Share Posted January 2, 2008 They didn't stop making them. Only the JMP versions. There are plenty of early/mid 80's JCM 800 1959's out there (4 hole/non MV). Not as common, but not hard to find Link to comment Share on other sites More sharing options...
Members atrox Posted January 2, 2008 Members Share Posted January 2, 2008 Oh... word... Lost context by just reading the one response. What clay said Link to comment Share on other sites More sharing options...
Members clay_finley Posted January 2, 2008 Members Share Posted January 2, 2008 :poke: Link to comment Share on other sites More sharing options...
Members telephant Posted January 2, 2008 Members Share Posted January 2, 2008 Oh... word... Lost context by just reading the one response. What clay said Link to comment Share on other sites More sharing options...
Members Burstbucker Posted January 2, 2008 Author Members Share Posted January 2, 2008 "The big difference is the PCB on mv 800'sis mounted to the pots, where as the JMPhas the board mounted on the chassis." My particular JCM800 is a 1983 model with vertical input jacks, the jacks and pots are all chassis-mounted with leads going to the chassis-mounted PCB, pretty good build quality really. Most amps aren't built this well knowadays. Link to comment Share on other sites More sharing options...
Members cap'n'crunch Posted January 3, 2008 Members Share Posted January 3, 2008 I have an 84 2204 with vertical inputs. Its a piece of history as it was the very last vertical input model to come down the assembly line. Nah, well, one of the last. But seriously, it is an 84 with vertical inputs. Link to comment Share on other sites More sharing options...
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