Going to Build a 2204, Should I Mod?

Clockworkmike said:
I guess that's it? I've read before that the notable difference is the JCM 800 had a cold clipper and technically 3 gain stages over the JMP having 2. Is this true? Cause I always believed that they were essentially the same amplifiers right down to the circuitry but that can't be true if this is the case, right?
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The preamp is very different before the tonestack between the non-master volume and the master volume JCM's... jcm800pr.gif

IMO, with the master volume/2204, the meatiest tone of this circuit doesn't happen till the master is about 6 or 7, regardless of where the preamp volume/gain is set at.
 
SG John said:
I agree with Mike, and would wonder what you're really going for. Owning a '78 2204 I can say it is a great sounding amp. Maybe go for the stock circuit first to see if it's what you're looking for, then start modding. Then, you'll have a reference point to go back to.

Personally, I think the '78-'79 2203 and 2204 are some of the best amps Marshall made, and finally got it right. Then they ruined it by creating the JCM800.
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I agree with this post
 
My first Marshall was a 1979 6550 MV 50 watt then my guitar teacher turned me on to the 4 input Marshall's
issue it's only a one trick pony one channel. I have serviced some outstanding 50 watt Marshall's all had 470 volts B+ not 350 volts
2008 hit the jackpot with the Green Hornet ODS 50 watt JTM 45 PT with a 784-139 OPT JTM 45/100 filter supply three way bright switch
mid boost switch clean channel cascade overdrive channel preamp boost rock/jazz switch in the middle it bypasses the tone stack
master volume and effects loop. Have fun with your build.

EL34 Mid Plate Skyliner 50 Watt 002.JPG
 
SG John said:
2203 and 2204 are both Master Volume heads. The 2203 is 100 watt and 2204 is 50 watt. They were the transition from the 1987 (50 watt) and 1959 (100 watt) to the the JCM 800. You could get all four (1987, 1959, 2203, 2204) under the JMP badge. I like both the 2 and four hole heads. Still think they finally got it right in '79 with the 2203, then blew it on the JCM.

Purely personal preference. I like the raunchy cleaner traditionally English sound of the JTM up to through the JMP. Even though many disagree, I think the amps lost some of their character with the JCM. Everyone can sound the same with a JCM. There's nowhere to hide with the earlier amps, and you'll definitely sound like you.
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I find it really hard to keep up with JCM, JMP, etc.
 
Clockworkmike said:
It's a pretty valid point honestly but a bigger question of "What changed from JMP to JCM?" On paper they SHOULD be the same but there IS a noticeable difference between the two, with the JCM becoming slightly more gainful and a little more compressed I guess you could say? But what I never understood is why? It's sort of a mystery really, especially among the first run of JCMs vs the last run of the JMPs
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All i know is the Origin 50H, when hot rodded by @syscokid, has more gain and bite than ANY stock Marshall i have played through.
 
Cadorman said:
I just ordered the chassis, face plates and double turret board from Valvestorm. It looks like Digi-Key has the Hammond trannys in stock, so I will probably get those unless anyone has a better idea that isn't outrageously priced. I have the Metroamp fx loop that I will install. Should I do any mods to improve on the stock circuit? More gain? I'm open to suggestions. I will most likely use Dale resistors again. Who's caps should I use? I'm not trying to replicate a stock circuit, but make it better.
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Build whole thing stock, and make sure it works 100%
before you try to modify anything.

The biggest problem with modifying is noise and or oscillations.

I might use JCM 900 transformers, which is the same as DSL transformers.
The advantage is that this power transformer has an extra secondary winding, for making low voltage power supplies. Plus Minus 16 volt DC supplies.
These low voltage supplies will be handy to power mods inside the amp , such as channel switching or DC filaments....
 
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SG John said:
2203 and 2204 are both Master Volume heads. The 2203 is 100 watt and 2204 is 50 watt. They were the transition from the 1987 (50 watt) and 1959 (100 watt) to the the JCM 800. You could get all four (1987, 1959, 2203, 2204) under the JMP badge. I like both the 2 and four hole heads. Still think they finally got it right in '79 with the 2203, then blew it on the JCM.

Purely personal preference. I like the raunchy cleaner traditionally English sound of the JTM up to through the JMP. Even though many disagree, I think the amps lost some of their character with the JCM. Everyone can sound the same with a JCM. There's nowhere to hide with the earlier amps, and you'll definitely sound like you.
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The 4 hole is a clean preamp, that overdrives the output tubes.
Therefore very loud to make it sound good.

The 2 hole is a distorted preamp which overdrives the phase inverter.
It has a master volume.
It was designed to get a better sound at a lower loudness.

The difference is the 2203/2204 has an extra gain stage in the preamp.
This doubles the sensitivity (compared to the previous /original plexi design).
The 2203/2204 is just a modified plexi....small differences.
 
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syscokid said:
What I would get is the CTS pots with brass shafts and the ARS filter caps, both offered at Valvestorm.

Which exact chassis did you get? Is it for a laydown power transformer or an upright power transformer?
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I second the CTS pots, for the money spent they are a good dependable pot (although sometimes the tolerance can vary a bit). I vote for ERO Vishay MKT1318 signal caps from Valvestorm. I have used them a lot and they are fantastic, Marshall used those on the Astoria builds. ARS filter caps or F&T's are both good choices.
 
Amp Mad Scientist said:
The 4 hole is a clean preamp, that overdrives the output tubes.
Therefore very loud to make it sound good.

The 2 hole is a distorted preamp which overdrives the phase inverter.
It has a master volume.
It was designed to get a better sound at a lower loudness.

The difference is the 2203/2204 has an extra gain stage in the preamp.
This doubles the sensitivity (compared to the previous /original plexi design).
The 2203/2204 is just a modified plexi....small differences.
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Isn't that why they kept the technical name Mk II on the JMP 2203/2204, because it just the next evolution of the previous amp? Someone told me that once anyways using that same logic with the 900 MKIII Master Volume ( though diode clipping became the next mod on that one) and the unofficial title of the SLX Master Volume: MkIV ( removed diode clipping added extra gain stage and preamp tube)
 
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