JMP 2204/JCM800 2204 questions

Discussion in 'Building the Classics' started by Sprocket, Aug 24, 2019.

  1. Sprocket

    Sprocket New Member

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    Hey guys! I'm quite new to amp building and when looking for some kits that interest me a ran across the 2204's. Being new I was looking at some kits (specifically from Ceriatone and the Metro kits offered at Valvestorm) and found a few things that confused me.

    I can't post links so to find the Ceriatone layout go to their website and then to the "British Style JCM800 2204 HW" -> Documentation -> Layout. For the Metro layout go to the Valvestorm website -> Build Checklists -> 2204 50 Watt -> 2204 layouts -> "2204r16.jpg."

    First, I was curious/confused on some of the differences between 2 similarly labeled amps. Obviously there are inconsistencies and changes between same model# amps (and also the possibilty that one is a JCM style and the other an older JMP style), but I wanted to make sure I understand and get some ideas at which might be a better layout to follow.

    1) Ceriatone's amp has 4 UF4007 diodes on the far left of the board that are not present on the Metro amp. From my understanding these 4 diodes are what create the rectifier right? On the Metro these are just located in its own little encasing on the right side of the layout.

    2)The Ceriatone kit has 50+50 500V dual axial (thats the correct term right?) electrolytic capacitor while the Metro has a 33+33 450 volt dual axial. I can find dual axial 33+33 450 volt capacitors but I cant find almost any 50+50 caps besides 1 website that had them on back order (I like the sound of the Ceriatones, but the shipping cost seems quite high hence why I'm looking to maybe source parts elsewhere.). I'm not planning to build this amp any time soon as it'll take a bit to get the money for it, but it made me question why there was no other sites that even listed 50+50 dual axial caps (All i see on the other sites are cans like these). Whats the deal? Also the Metro kit has one of the cans as a 33+33 450 volt as well. Any possible significance for this change or the result of it?

    3) Is there any overall drastic tonal changes that might be the result of the 2 builds? Is one more of a JMP style and other a JCM or what might the differences signify.

    I'm sorry for the extreme load of questions! I tried to do some of my own research and was coming up short especially when trying to find gut shots for references. I tried to take a look at some of the Joe Popp JCM800 2204 builds but I couldn't see exactly what the values were, and he listed a Ceriatone 2204 layout that was different itself (though the post was dated at 06/09/07 so it was likely an older version) so that only confused matters. I'm curious on what some thought you all have on this and would be grateful for any questions you could clear up. Thanks in advance!
     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    "From my understanding these 4 diodes are what create the rectifier right?"

    Yes

    "Any possible significance for this change or the result of it?"

    The 33uF caps store less energy and will produce more sag. But also more hum, because there is less filtering of the ripple in the power supply.

    "Is there any overall drastic tonal changes that might be the result of the 2 builds?"

    Tone is subjective. What sounds "better," is in the ear of the beholder.
     
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  3. Sprocket

    Sprocket New Member

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    Thank you. That clears things up a bit more when it comes to the tonal differences between the 2 layouts.
     
  4. ampmadscientist

    ampmadscientist Well-Known Member

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    In a layout parts on the board radiate into each-other.
    And so there may be much more going on than what the schematic shows.
    For example, 2 coupling caps side by side can radiate into each-other.

    There are 2 caps on the board, but in between those 2 caps is a third capacitor (formed in the air space between the 2 caps)
    There is more audio path than what the schematic is showing depending on the layout of the components on the board.
     
  5. Chris-in-LA

    Chris-in-LA Well-Known Member

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    I built the Valvestorm kit and find that it compares favorably soundwise to my real ‘88 jcm800 2204. They also use a steel chassis that will fit into a 50 watt style Plexi cab. The real jcm800 ‘s I have use only the 50uf cans but I don’t hear much difference between them and the clone.

    http://www.marshallforum.com/threads/metro-2204-clone-build.105671/
     
  6. Chris-in-LA

    Chris-in-LA Well-Known Member

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    I hope that’s helpful.
     
  7. Sprocket

    Sprocket New Member

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    Yes! Thank you so much! I was curious about some of these differences and though the valvestorm kit looked awesome, I wanted to check and make sure I was going to be getting something that wouldn't overly alter the sound of originals. I also love the look of plexi style cabs so this would work great for me. Thank you once again for the reply and I'll check out your build post for sure.
     
  8. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Last I checked, the Valvestorm chassis was 1/4 inch deeper than a stock Plexi. You have to make sure your head cab is the right size. Sourmash will build you one with any dimensions you want for the price of their regular Plexi cab.
     
  9. Exojam

    Exojam Well-Known Member

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    My Valestrom 50 watt clone is pretty damn quite using those 33’s.

    I personally think it is a great sounding amp and was fun to build.
     

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