Marshall JMP Master Model 2203 MK2 100watt MODS

Discussion in 'Marshall Amps' started by Gohanndes, Oct 23, 2021.

  1. Gohanndes

    Gohanndes New Member

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    Hi,

    I have a Marshall JMP Master Model 2203 MK2 100watt and want to do the negative feedback mod. Which resistor on the board should be changed? and What is the recommended value to get a JCM800 feel?
     
  2. South Park

    South Park Well-Known Member

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    You need to change the input to a cascade circuit to get the jcm feel not the negative feed back
     
  3. Gohanndes

    Gohanndes New Member

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    and... how exactly do I do that?
     
  4. Rockat

    Rockat Active Member Silver Supporting Member

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    Yeas ago I tried this mod on a JMP 1987 and it took it out again as it destroyed the character of the amp IMHO
     
  5. Gohanndes

    Gohanndes New Member

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    ok! what mod do you recommend for this amp?
     
  6. Rockat

    Rockat Active Member Silver Supporting Member

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    Trying to get it sound like a 2203 as far as know is not practicable. I have both (well 2204). The only one I did to mine was a mod to get one volume to act as preamp vol. This allows me to get a great overdriven sound at usable volumes. My Tech did this for me so I don’t have the details. But the two amps are fantastic beasts. I could not pick a favourite, there both great amps but different!
     
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  7. Ufoscorpion

    Ufoscorpion Well-Known Member

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    Legendary tones hot mod v2 if you’re after more gain , well more everything really .
     
  8. tschrama

    tschrama Well-Known Member

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    Jmp 2203 allready has three cascaded stages.

    If you tell us what you want to achieve, we could give you some directions.
     
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  9. Gohanndes

    Gohanndes New Member

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    Well, originally I was interested in doing the NFB mod but I don't know which resistor to change and what value should I use.
     
  10. johan.b

    johan.b Well-Known Member

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    People need to read with more attention.

    If you allready have a jmp2203 you have the same circuit as a jcm800 2203.

    Later 800s have higher voltage and fewer caps but arranged for same capacitance and a 100 pF cap across anode/ cathode on the input stage, taking the highest highs down a bit.

    Enjoy your amp... many people are envious of what you've got....
     
  11. Gohanndes

    Gohanndes New Member

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    Thanks! :cheers:
     
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  12. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    :cheers:
    :welcome:
    To the forum
    I personally would not mod this amp.
    But that is not what you want to hear, I had the 2104 version and I had thought it was the greatest Marshall I have ever owned.
    Hope you get what you’re after !!
     
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  13. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    What tone/feel are you looking for out of the mod? I can help you but I’m not sure about the mod you are speaking of. Lowering the resistor value will increase the negative feedback and make the output section less aggressive up to the point of breakup. I don’t know how hard you push the power section, it’s 100 watts so it’s powerful. Using a smaller resistor will also increase the amount of presence. You’ll have to adjust to taste. Increasing the NFB resistor will make the amp more aggressive and reduce the presence.
     
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  14. Matthews Guitars

    Matthews Guitars Well-Known Member

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    My advice: Unmodded original JMP 2203s are NOT getting more common. Every time someone mods one, there's one less original example. And they're becoming too valuable to look at as mod candidates.

    So...don't mod it. If it's not the amp you are looking for, you'll have NO trouble selling it, for an average price of something in the neighborhood of 2500 dollars. Somebody wants it, in its ORIGINAL condition, and will pay that to get it.

    Then apply that money to a lower cost amp, or maybe even a kit, if you want to go that far, and use that as your basis for modifications. Get the amp you want without modding a classic.

    I won't do a mod to a 2203, not even an effects loop, unless the mod is 100 percent reversible. That means adding no holes to the chassis.
     
  15. Drinkingdeath01

    Drinkingdeath01 Well-Known Member Gold Supporting Member

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    Like someone mentioned above me, I wouldn't mod this amp. It's worth more stock then what you want it to do. If your not into it, I'd sell it and buy what your looking for.

    I'm not anti-mod by any means but these stock are getting harder and harder to come by.

    Good luck on your quest for the tone your looking for !!!:cheers:
     
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  16. william vogel

    william vogel Well-Known Member Gold Supporting Member

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    I just finished a 2204 build. I posted in Building The Classics section here. I agree with everyone here about leaving it original. It’s your amp but I don’t know what you would you need to change.
     
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