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JMP 2104 adding fix loop

Discussion in 'Marshall Amps' started by nightraider43, Sep 14, 2021.

  1. nightraider43

    nightraider43 New Member

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    Hey guys, have a question concerning adding an fx loop to my ‘78 JMP 2104. So I don’t want to modify my amp in any way, as in drilling two holes and what not for say a Metro zero loss. This amp is mint and all original. Is there anything out there worthy of plugging in my time based effects? They are “okay” going straight in but my carbon copy delay sounds nothing like it use to in my other amps with a loop. My reverb and chorus surprisingly sound pretty damn good going through front but I’m sure would sound better in a loop. Thanks for any input! Steve
     
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  2. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    I have no idea what to tell you, but I had the same amp way back when, the delay I used was a maestro echo plex into the front, as we all did back in the early 80’s.
    And I have to agree on not modding it.
    Excellent amps..
    Cheers
    Mitch
     
  3. Ufoscorpion

    Ufoscorpion Well-Known Member

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    Worth considering a Fryette power station .
     
    Last edited: Sep 15, 2021
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  4. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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    IIRC, someone here mentioned mounting an aftermarket loop kit in an external box so as not to drill holes in their chassis.
     
  5. marshallmellowed

    marshallmellowed Well-Known Member

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    Yeah, your options are pretty much limited to, as mentioned, a loop in an external box, maybe velcro'd to the top of the chassis, or an attenuator with an FX loop. Adding a loop to the amp, even without drilling holes, would still require inserting the loop wiring into the circuit (soldering...), but could easily be reversed. If you have no desire to spend big bucks on an attenuator with a loop, that would be your best option.
     
  6. black knight

    black knight Active Member

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    Good responses here with viable solutions. The PS is what worked for me as I prefer 50 and 100 watt NMV and MV Marshalls, and also prefer time-based effects after an overdriven preamp/PI and output section (to the extent that the power tubes/OT can be overdriven). I wound up getting a used PS2 for about $600 USD. For years I had a hard time spending that much on something that didn't necessarily musically "enhance" whatever rig I was pursuing. After experiencing it I know I should've done it a long time ago.

    Not only would the PS solve your issue of getting time based effects post preamp, but post preamp AND output sections. In addition, your amp can be set to where it sounds best, which is almost certainly too loud in almost any situation, and still retain its goodness at a lower volume. It is also useful with a MV amp such as your 2104. I know everyone is different but I like to run that circuit with the preamp backed off a bit and the master goosed up generously. Kind of walking the line between a NMV (1959/87) and a MV (2203/4). The cool thing is that it can be used with all your amps if you happen to have several like a lot of us do.

    There are other advantages as well which I encourage you to explore. In the end, you'll likely find, as I did, that the expense was worth it. Good luck in finding something that works for you.
     
  7. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    I have a Bad Cat Unleash 2 that is a reamper and attenuator with a loop built in. It also has a second volume control for a volume boost in case you ever use that type of thing.
    In any case, I vote for attenuator with loop.
     
  8. eastwood6

    eastwood6 Well-Known Member

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    As a former 2104 owner, I beg of you, pleeeeeze don’t hack up that beautiful vintage amp.

    I’ve been playing Marshalls with pedals for more than 40 years and never used an effects loop. Have been told it sounds pretty good.

    Unless you have extensive rack effects, stick those pedals in front of the amp and play.

    It’s a Marshall JMP. The very definition of rock tone.
     
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  9. fitz288

    fitz288 Well-Known Yinzer Silver Supporting Member

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    Same.
    Same.
     
  10. Rozman62

    Rozman62 Well-Known Member

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    You will most likely regret modifying down the road. It will reduce the market price and you will be out of pocket. Spend the $ and buy a Fryette power station. You will preserve the tone of the amp as well as the amp itself while getting a quality loop. It also reamps if you have lower watt amps you want to gig with but can't. Direct out to your DAW for recording if needed. Bring to a gig and if your tube amp craps the bed then you can still use the power amp with an OD direct to the FE to finish the gig. It's not cheap but loaded with functionality. I have a '79 2104 in a 2204 box and have a PS on the way.
     
  11. Jethro Rocker

    Jethro Rocker Well-Known Member Silver Supporting Member

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    Is that an L6-S in your avatar?
     
  12. Rozman62

    Rozman62 Well-Known Member

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    Yes sir.
     
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  13. nightraider43

    nightraider43 New Member

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    Did some research on the PS 2 and that really seems to be what I’m looking for. Thanks for all the input guys. Probably end up selling an amp to purchase one. My DSL40 has been collecting dust since I picked up my 2104. The 2104 is simply magical.
     
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  14. Rozman62

    Rozman62 Well-Known Member

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    Understandable why you don't use the DSL 40 when you have a 2104. Only common denominator is the name on the grill cloth...get rid of the wannabee.
     
  15. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member VIP Member

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    I could sell 3 of my wannabe amps and still not be able to grab a 2104 of my yesteryear. So that is not a viable solution.
    Thanks
     
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  16. Matthews Guitars

    Matthews Guitars Well-Known Member

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    The 2104 is a 2204 chassis in a combo shell. So...there simply aren't any available factory made holes in the chassis to add an effects loop in. Unlike a 100 watt chassis (2203 or 1959) which has four punches for speaker jacks, and four punches for input jacks, behind the front and rear panels, the 50 watt chassis simply doesn't have those.

    So....there's no simple way to add the loop. If you want to preserve originality then it's just the wrong chassis for that.

    In a 100 watt chassis, a loop could be added in a fully reversible manner.

    The way I put a Metro FX loop into a 100 watt chassis is to use two of the four speaker jack holes, and pick one potentiometer
    to be replaced by one with an integrated push-pull switch so the loop can be manually switched on and off from that knob.
    This gives full reversibility as long as I keep the original pot.
     
  17. pedecamp

    pedecamp Well-Known Member

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    Get a Bad Cat Unleash. Look them up and read about its features.
     
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  18. marshallmellowed

    marshallmellowed Well-Known Member

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    Last edited: Sep 26, 2021
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