Marshall Experts- What's the deal with ____?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jackaroo, Aug 8, 2008.

  1. jackaroo

    jackaroo Member

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    Jumper cables vs. Y cable vs. Internal jumpers on the inputs on the typical 4 holer Marshall 1987X or JTM-45?

    What's the difference in terms of tone and what is actually happening to the circuit?

    Thanks-

    J
     
  2. Blue Strat

    Blue Strat Member

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    A Y cable would feed equal signal to both channels so with the volume controls set equally, you'd hear a 50% mix of each channel. Using a jumper cable you get more of the channel you plug directly into (hi input) and less of the jumpered channel with the volume controls set equal.

    Internal jumpering can be done in a variety of ways and could result in either of the 2 situations above.
     
  3. jackaroo

    jackaroo Member

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    Thanks Mike-

    That seems pretty definitive... heard that internally you can get more gain than from a Y. True?

    Where do I find a good Y cable or adapter?


    J
     
  4. mark norwine

    mark norwine Member

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    The 2 channels are voiced differently. Using both allows you to use the 2 volume controls to mix bright & dark. That's why folks do this.

    You don't need a Y per se....

    Plug your guitar into either jack of either channel. Let's say "hi level" jack of Ch 1. Next, take a jumper (any short guitar or pedalboard cable) from the other Ch1 jack and plug it into the "hi level" jack of Ch 2.

    Done.

    Tyr it.
     
  5. brad347

    brad347 Member

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    just for the record, it works because the two jacks on each channel are internally connected. This seems obvious to point out, but lots of people are confused by it because they don't understand how the signal can go "out" an "input."
     
  6. jackaroo

    jackaroo Member

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    Mark I understand how that works and how the channels are voiced.

    I was looking for a more technical distinction between the two. Apparently there's something to do with the Y having more gain because you're not coming out of the low of one channel into the high of another. And I'm told that the internal jump has more gain still...like a lot more.

    Ah well-

    J
     
  7. jackaroo

    jackaroo Member

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    Funny enough it was reading that page (and not understanding it) that prompted me to ask here. I tried to join that forum, but they're not taking new members so for now the best I can do is use their search function. I figured I could get confirmation of what they were saying...and hopefully with a little less tech-speak. I really have to get a soldering iron and start trying some mods.

    J
     
  8. Blue Strat

    Blue Strat Member

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    As I said, there are any number of ways to do this so there's no single result. Can't think offhand how you'd get more gain on both channels in a standard Marshall circuit though unless you also modified something unrelated to the jumpering of the channels.

    I've done the jumpering in my 50watter and it's pretty much like using a Y cable.
     
  9. Bo Faulkner

    Bo Faulkner Member

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    :messedup:messedup:messedup:messedup hehe for something as simple as how to plug into a Marshall that was some deep stuff.

    I use a y and go for it.. My germino does not need a y or a jumper (bright cap difference??) I actually prefer my germino without jumping it (loses a touch of bite to my ears when jumped) My Marshall has to be jumped (or y cord) unless you are running REALLY loud. The bright cap is a beast on it.. thought about snippin it but too lazy to open it up
     
  10. hogy

    hogy Member

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    Jack, you may know this already, but a cool little trick is to use channel jumpering as a quasi effects loop. Plug your guitar into input #1 of your favorite channel, out of #2 of the same channel and into your effects unit (reverb, delay, etc.), and into the other channel.
     
  11. jackaroo

    jackaroo Member

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    Yes sir.

    I learned it right here....from you!
     
  12. jezzzz2003

    jezzzz2003 Member

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    I cant understand why an internal jumper might have more gain than using a short patch cable personally,

    Technically, the hi input on the treble channel seems to add lots more gain than any of the others purely because theres loads more bight in the top end and thats whats distorting, it was an old trick with these amps before treble boosters came about to use the presence control full up because it also adds more distortion.
     

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