A Marshall Question

[bubs_42]

Is the JPM and the JCM800 to completely different amps? Notice they were both badged 2204, just wondering, because I'm interested in finding a JMP 50 watter, the one I found in Ohio sounded great but it need some work (Scratch Pots, Broken Knobs, just plane dirty) and I would already be deep into it.

[Turdus]

Is the JPM and the JCM800 to completely different amps? Notice they were both badged 2204, just wondering, because I'm interested in finding a JMP 50 watter, the one I found in Ohio sounded great but it need some work (Scratch Pots, Broken Knobs, just plane dirty) and I would already be deep into it.

I'm fairly certain that the early JCM800 innards were very close to, if not the same as the later 70's JMP heads.

This changed in '82 or '83.

ETA: If the JCM800 has horizontal inputs and brass handle caps, it is an early one.

[bubs_42]

Interesting. I love the drive this amp had, it's what I here in my head. The more I learn the more I realize that my approach to getting what I think I hear is a little off. Not bad just not exact.

[DavidE]

Were you looking at a 2 input master volume amp? I have a 50 watt JMP, but it's a 4 input, non-master, head. Great amp, but you have to crank it!

I was playing through a 2553 head when you saw me Friday night.

[bubs_42]

Yep it was a 77 Master Volume, verticle inputs. Your amps sounded fantastic Friday, I didn't intend on trying it, but I figured "Hey why not", wish I never did. The Master Volume was great and it could be played at a NON- Earbleed levels and sound great. I checked Ebay for some price's but they were all over the place. Ruffer one's going for more, nicerones going for less. Don't know. Anyway, this all stems from my great search for an older Dr Z. SRZ, they are producing them again but I want an Old Large Box version for the Mojo Factor. And if it sounds as better that this amp then I am holding out for one.

P.S. Dave you really have to much Sh#t.. McCarty+Korina=Tone.. I'm not sold on PRS PUPs though..

[Craig S]

Going to Dave's house is more fun than going to GC....he has cooler stuff

[Hackubus]

I've got a '77 JMP & an '82 JCM 800. Both have similar sounding voicings. Haven't cracked em open to look inside however. Afraid I'd let the magic smoke out.

The JMP is a MONSTER though!

[AdmiralB]

ETA: If the JCM800 has horizontal inputs and brass handle caps, it is an early one.

Other way 'round - the vertical inputs are the earlier.

If we're talking only master volume amps, then late-'76 through '83 are 99% identical. Sometime around '82 they made a subtle change in the presence circuit (earlier has DC on the pot, like a tweed Bassman - scratchy when you adjust it), but it's not audible IMO.

'75-'76 MV amps are a unique circuit, just added a master to the old amps. Very thin at low volumes, less gain (SUQ, in other words).

In '84 the PCB changed (horizontal inputs) and the amount of filtering was altered (affects the 100W more than the 50W). The circuit stayed the same but the layout was changed and the PCB was kinda screwed up, so they added some snubber caps to keep things stable. As a result, the later amps might have a little less 'sparkle'. It'd be a subtle thing on a stock amp, though.

[bubs_42]

Thanks that's what I'm looking for. The JMP had balls. Even at lower setting and the Marshalls that I'm used to didn't change much when you move the controlls around. This one sounded responsive to different settings. Once I set it where I wanted it at around 9 0'clock on the volume. It I went higher all I had to due was pull back the highs a bit and I could dail in that tone all they way to 12 O'clock which is as high as I wanted to go in the store. I shouldn't say ton's of gain, but the right amout and I just wanted to riff a day.

Just wanted to know more and thanks again, just got back from jamming on my Tremoverb which is a beast of an amp. I set both channels to vintage and the Red Channel toggle to modern, Drive about 1 o'clock. Sounds fantastic.

[AdmiralB]

Well, another thing with Marshalls (really any amp prior to the early '90s) is...they're all HIGHLY variable. Parts tolerances weren't what they are now, so they're all gonna be a little different.

[bubs_42]

Well, another thing with Marshalls (really any amp prior to the early '90s) is...they're all HIGHLY variable. Parts tolerances weren't what they are now, so they're all gonna be a little different.

That's what I was afraid of... If it's good it's good. But sometimes I get ahead of myself and didn't want to regret the purchase later. I think I know some guy's that would swoop it up for me if I change my mind. Thanks again AdmiralB.

[DavidE]

Well, another thing with Marshalls (really any amp prior to the early '90s) is...they're all HIGHLY variable. Parts tolerances weren't what they are now, so they're all gonna be a little different.

That's what I was afraid of... If it's good it's good. But sometimes I get ahead of myself and didn't want to regret the purchase later. I think I know some guy's that would swoop it up for me if I change my mind. Thanks again AdmiralB.

Where was the Marshall? If at GC, my bass player works there.

[bubs_42]

Well, another thing with Marshalls (really any amp prior to the early '90s) is...they're all HIGHLY variable. Parts tolerances weren't what they are now, so they're all gonna be a little different.

That's what I was afraid of... If it's good it's good. But sometimes I get ahead of myself and didn't want to regret the purchase later. I think I know some guy's that would swoop it up for me if I change my mind. Thanks again AdmiralB.

Where was the Marshall? If at GC, my bass player works there.

Damn, it's a SamAsh ! They were asking $1250 for it that's what kept me away. Ebay is so all over the place it's not even funny.

[Turdus]

ETA: If the JCM800 has horizontal inputs and brass handle caps, it is an early one.

Other way 'round - the vertical inputs are the earlier.

yes.. that is what I meant to say. I should not post before 11 am, or 2 cokes... whichever comes first.

[riffpowers]

The JMP and JCM800 2203's and 2204's have the same components, but the internal voltages are tweaked on the jcm800 to make it a bit more aggressive compared to the slightly smoother and warmer JMP.

[peedenmark7]

the '76-78 jmp master volumes have a very different preamp section than the '79 and later which carry the 800 circuit or an early version of it.

some love the change, but I never cared much for the 800's fizzy sounding preamp circuit so to me those amps pale in so many ways to the earlier version.

many would argue this point.

79-80's look the same as the earlier versions having the small check grills,though in general you will see black dust covers that say marshall on the later rather than the old rola logoed cover with gold decal denoting the speakers as g12m or H.

from my experiences the later speakers with the "marshall" dust covers are usually g12-65s [nice speaker]

any conflicting info there?

if you'd like more in depth info as to what to look for shoot me a pm.

I'd say stay away from an 800 unless you have a good eq.

they lack warmth and depth [bass] , the highs are tinny,

and mids are over the top.

[Brewmaster]

if you'd like more in depth info as to what to look for shoot me a pm.

I'd say stay away from an 800 unless you have a good eq.

they lack warmth and depth [bass] , the highs are tinny,

and mids are over the top.

Simple mods are out there to fix the thin ear piercing highs, give more sweep over the tone controls, balance out the mids, and add bottom end. 800's can be real thick and beefy when the mods are done correctly.

[AdmiralB]

The JMP and JCM800 2203's and 2204's have the same components, but the internal voltages are tweaked on the jcm800 to make it a bit more aggressive compared to the slightly smoother and warmer JMP.

Most of the JMP 2204s have a lower-voltage secondary on the PT - so the power tubes are sitting around 380V. Most 800s have around 475V, so all the tubes are seeing about 25% higher potential, so yes, that is different. The 100W amps all are around 470V, though - no changes there.

the '76-78 jmp master volumes have a very different preamp section than the '79 and later which carry the 800 circuit or an early version of it.

That early circuit is only in '75s and early '76s. The later circuit came along in late '76, certainly all '77s and later had it.

[RacerX]

I agree the the 76-78 50watt masters are great. another little difference is the caps changed to little square-ish "lego caps" in early 78 I think. imo the 76/77 are the ones to get. put in a nice vintage 12ax7 in the first position and you are good to go, no pedal needed to hit old-school Priest/UFO/AC-DC/Purple tone especially with a bucker.

But they DO vary and some can be a little thiner sounding. Find a sweet/thick one and pay a few more bucks if you have to. The 77 I sold to Barry (bmenary) was just KILLER with the matching 4x12. It was running el34's and a very special amperex 12ax7.

Most of the Marshall geeks prefer the non-masters (4 hole) but those are just way too loud before they hit the sweet spot. If you play outdoor festivals, plexi's and 4 plugers are great. but for me the the Masters have always been the tone I was looking for.

Mark.