Jmp /jcm 800

Discussion in 'Marshall Amps' started by RLC, Apr 4, 2021.

  1. RLC

    RLC New Member

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    Are they the same? Are combo and heads the same?
     
  2. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Generally yes. There are SOME differences depending on which model(s) you're referring to, but usually it's the same circuit in the chassis, but the chassis itself changed. The full width faceplate of the JCM800 series is, for some models, the largest change to the amp that was made. A 1959 is a 1959 whether it's a JMP or a JCM800.

    As always, the one consistent thing about Marshalls is that they were never consistent for very long. They always changed something sooner or later.

    As an example, your 2203 or 2204 kept the same general circuit UNTIL the JCM800 version was changed to horizontal rather than vertical input jacks.
     
  3. RLC

    RLC New Member

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    Is there a notable difference in tone between vertical and horizontal inputs?
     
  4. Matthews Guitars

    Matthews Guitars Well-Known Member

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    I can't attest to that myself. I'll leave that to someone who can.
     
  5. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Don’t forget that some JCM800’s have a single input jack with channel switching and diodes for extra distortion.
     
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  6. scozz

    scozz Well-Known Member Gold Supporting Member

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    I did not know that.
     
  7. scozz

    scozz Well-Known Member Gold Supporting Member

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    I've heard others say there is a difference, and that the vertical input JCM800s are slightly more sought after by those in the know.

    But I've never heard anyone articulate the actual differences.
     
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  8. Trelwheen

    Trelwheen Certified B.S. Launcher Double Platinum Supporting Member

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    I think the main difference between the vertical and horizontal input versions is that on the vertical ver. the input jacks, pots and tubes are chassis mounted with flying leads to the PCB. On the horizontal models the input jacks, pots and tubes are PCB mounted.
     
  9. AndyD

    AndyD Well-Known Member

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    This is a significant difference in my opinion. I would always go for the early amps ......ie jmp 2204 or vertical input Jcm800.
     
  10. Chrome

    Chrome Firebird Freak Gold Supporting Member

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    I own a '76 JMP 1987 and a '78 JMP 2204. both 50 watt heads. In this specific example there are differences. the 76 being a NMV and the 2204 being a MV with a cascaded pre-amp. I can get break up quicker at lower volumes on the 78 than I can the 76. tone wise, they are very similar to a point. the 2204 in my opinion is the better of the two simply because I can get both with it. if I dime the master and control volume with the pre-amp I get very plexi like tones, If I dime the pre-amp and control volume with the master, I get very JCM 800 tones. it's just a matter of personal preference.
     
  11. Chris-in-LA

    Chris-in-LA Well-Known Member

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    The vertical input 100 watt 2203 heads usually have more filter caps than horizontal input models. I haven’t played any of the earlier ones so I can’t tell you what more filtering does.
     
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  12. AndyD

    AndyD Well-Known Member

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    I totally agree. I often quote how versatile the 2204 is. I am still discovering the secrets of this amp. If I find that it really can do everything that my NMV amp can do, them the latter may have to go. They are that good, in my opinion.
    To answer the OPs question, the amps are exactly the same in a combo as in a head. At least that’s true for the early JMP and JCMs.
     
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  13. JP2036

    JP2036 Well-Known Member

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    No not all the same.
     
  14. RLC

    RLC New Member

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    Seems to me that the JCM 800 are more sought after.
     
  15. Ufoscorpion

    Ufoscorpion Well-Known Member

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    What people need to realise is it’s hard to find two jcm 800 / jmp mv’s that sound the same period , let alone difference’s between vertical and horizontal inputs .
     
  16. Saxon

    Saxon New Member

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    2204's did not change, even when the horizontal inputs came along. 2203's had a filter cap change, first from 6 to 5 caps (1984) then to 3 (1985?). 2205/2210 changed late in the 80's.
    As Ufoscorpion says, even the same amps from the same time period sound different.
     
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  17. AndyD

    AndyD Well-Known Member

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    Though I can’t disagree with what you have said, I think we are opening a can of worms here. In general terms, the JMPs sound a bit different to JCMs....yes. “Are combos and heads the same?”......in general yes because the heads were designed to go in either a combo or head. Obviously sonically they are going to sound different because a combo is open backed and a head can go on anything.
     
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  18. LPMarshall hack

    LPMarshall hack Well-Known Member

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    Significant in sound? How so (not questioning you, genuinely curious...)?

    Seems to me one may be easier to work on, but not sure if/how it could affect sound/tone.
     
  19. Travis398

    Travis398 Well-Known Member

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    I think they changed some of the components through the years even if the circuit stayed the same.
    Probably makes a little difference, I think the earliest ones had mustard caps.
     
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  20. Kelia

    Kelia Well-Known Member

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    Dave Friedman said that JMP's had better transformers than JCM800's ,
    I have a 2204 1979 JMP and a 1985 JCM800 , the JMP has a sweeter tone
    maybe because there is less plate voltage , some had high V and some had low iirc.
    When my tech made a mistake and fried the OT in my 1985 JCM , I found a 1978 JMP OT and when installed ,
    the amp had more low end bark with the JMP OT compared with the previous one.
     
    Last edited: Apr 6, 2021

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