jmp 2203 speaker outs?

Discussion in 'Marshall Amps' started by tritone, Feb 10, 2011.

  1. tritone

    tritone New Member

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    Hi,

    I recently bought my first real amp. A 1978 Marshall JMP. On the back it has two speaker outputs but they are not labelled. Which one do I use and what is the second for? The only mod to this amp is an ohm selector switch in case that makes a difference to my question.

    Thanks:)
     
  2. charveldan

    charveldan Well-Known Member

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    Got any pic's?
     
  3. tritone

    tritone New Member

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    i'll have to take some tomorrow and put them up.
     
  4. charveldan

    charveldan Well-Known Member

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    [​IMG]

    [​IMG]

    I've got two 78's, they both have 4 speaker outs as the amps made for the US had to in the 70's to be UL rated for insurance purposes.

    Your amp will either have 2 or 4 speaker outs as JMP's had no loop, unless your was modded, that's why i asked for pic's.

    It's important that you match the cab's impedance to the amp.
     
  5. Clammy

    Clammy Well-Known Member

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    The 2 speaker outputs are wired in parallel. You can use 1 or 2 cabinets (if using 2, make sure they're both the SAME impedance). Set the impedance selector to match to total impedance. For example, if using a single 4, 8 or 16 ohm cab, set the selector to match the cab's impedance. If using 2 8 ohm cabs, the selector needs to be set to 4 ohms, if using 2 16 ohm cabs, the selector needs to be set to 8 ohms.

    Cheers!
    :dude::dude::dude:
     
  6. Frankie

    Frankie Well-Known Member

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    If you're only using one cab either output works fine. The one closest to the impedance selector is wired up directly to the OT, so being anal retentive about shit like that, I normally use that plug just in case some bus wire wants to burn up on me and take out my OT by using the other jack.
     
  7. Frankie

    Frankie Well-Known Member

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    Dave's livin' the American dream over there in the UK.

    Hot chick? Check.
    Rock & Roll band? Check.
    Party liquor? Check.

    Now all you need is an opium den.
     

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