Is this a bad idea?

Discussion in 'Marshall Amps' started by mcblink, Feb 9, 2020.

  1. mcblink

    mcblink Well-Known Member

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    I have a DSL100H.
    There are 3 output jacks on the rear panel. One 16ohm and two 8ohm jacks.
    I always run the 16ohm jack into a 1960a, obviously at the cab, it's also 16ohm.

    Here's my question: let's say I also have a shitty Line 6 4x12...There are two jacks on this cab, both are 8ohms/stereo when used at the same time, but when in mono and use only one jack, it's 4ohms.

    Is it possible to use the 16ohm jack from the head to the 1960a, and then use both the 8ohm jacks from the head to run to the shitty Line 6 at the same time? This would put a cable in all three holes in the head...

    It's just a thought I had, I don't really have any real intention of trying this....but if I were to try it, what would I fry? ....or would it be ok? Hypothetically speaking, of course...
     
  2. FracStrat

    FracStrat Well-Known Member

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    NO !! I mean YES !! ( It’s bad idea )
    Take the line 6 cab and Re-wire it first !!
     
    Last edited: Feb 9, 2020
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  3. mcblink

    mcblink Well-Known Member

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    I know you're right....but
    I mean, the way I described how I was considering connecting everything,..ohms all match up everywhere, nothing mismatched...just that I would have to use all 3 output jacks from the amp...

    For now, the Line 6 cab is being used as an extra vocal monitor in our jamspace and I probably won't do anything different with it, but I just got to thinking about it (sometimes thinking about stuff has disastrous consequences for me lol) and figured I'd ask the nice friendly folks at the Marshall Forum what they may say
     
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  4. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member

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    What normally happens is once you use both of the 8 ohm jacks is the 16 is done, nothing comes out of it, I think I could be wrong but I am not sure.
     
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  5. Michael Roe

    Michael Roe Well-Known Member

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    Definitely a bad idea!
    Marshall really started confusing people when they went with the 5 speaker jack option. It made more sense when they only had two jacks and an ohm switch.
    You could just wire your line 6 to 16 ohm then use the 8 ohm jacks.
     
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  6. mcblink

    mcblink Well-Known Member

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    So again, not gonna do this, but was wondering hypothetically
     
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  7. FracStrat

    FracStrat Well-Known Member

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    Hypothetical Wonderer !!!
     
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  8. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

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    The problem is the 2 x 8s out of the 8 ohm jacks. These are meant for EITHER 1x8 or 2x16. That is the issue. You COULD, according to @santiall , run the 16 ohm out of 1 of the 8 ohm jacks and and one side of the stereo 8 ohm out of the 4 ohm jack. This is not a mismatch if you have multiple outputs and no impedance switch. All jacks are active at the same time.
     
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  9. ampmadscientist

    ampmadscientist Well-Known Member

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    No you can't do that because
    2X 8 ohm loads = 4 ohms (the shitty line 6 cab)
    +
    1X 16 ohm load (1960a cab)

    Total load =
    4 ohms X 16 ohms = 64
    4 ohms + 16 ohms = 20

    64 divided by 20 = 3.2 ohms, not allowed. Even if you hook all the speakers to the 4 ohm out, it's still too much load.
     
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  10. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

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    While this is correct, thats not how the multiple jacks work on these amps.
    You can do as Ive stated above. As per.

    santiall said:
    Plug the 16ohm cabinet into the 8ohm output and the 8ohm cabinet into the 4ohm output. That's perfect impedance match.

    Don't worry either about the output transformer myth, there is no problem with mismatching loads in any amps or splitting the load as long as there are available outputs, this is not any JVM exclusive feature, it is just plain physics. As long as there is a load connected properly you'll be safe, danger comes with intermittent connected loads, poor cabling, etc, but a mismatch by itself won't cause any harm.

    From the designer of the JVM, Jubilee Reiisues etc.
     
  11. Gutch220

    Gutch220 Well-Known Member

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    This is why I hate dedicated jacks for specific ohms in amps. I'd much rather have a knob to choose the impedance.
    It's obvious that they designed the amp to be used with one 16ohm cabinet OR two 16ohm cabinets (8ohms). I'm not sure if the circuit is designed to bypass the single 16ohm jack when both "8ohm" jacks are used (probably not). This is a possibility I guess, and you'd have to look at the jack itself, or the schematic. I'd bet somebody on here could help you more.


    It would be easier if they labeled jacks like this (or just put a knob like older Marshalls)
    upload_2020-2-9_13-50-52.png
     
    Last edited: Feb 9, 2020
  12. ampmadscientist

    ampmadscientist Well-Known Member

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    If you rewire the shitty Line 6 cab to 4 speakers 16 ohms then you can use all the speakers.
     
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  13. Gutch220

    Gutch220 Well-Known Member

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    ^yea, I'd imagine this would work no problem.
     
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  14. LPMarshall hack

    LPMarshall hack Well-Known Member

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    OH wow...I never knew this. I have a 16ohm 4x12 and an 8 ohm 2x12. So he’s saying I can plug them both into (a JMD...has a 16,8, and 4 ohm Jack) the amp, but just halve the loads? Awesome to know
     
  15. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

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    Yup.

    The new ones are labelled like this. Seems fairly apparent to me however one can still run it as Ive mentioned above safely. By halving the loads, you get two half loads which is one full load. This is not a mismatch.

    The picture of the speaker jacks above also show why you cannot run 2x 8ohms in the 8 ohm jacks.
     
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  16. LPMarshall hack

    LPMarshall hack Well-Known Member

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    And I’m surprised to hear what he says about load mismatches being no problem. I always read that the slightest mismatch meant instant death to the amp and the user.

    well I’m sure someone will chime in that Santiago doesn’t know shit
     
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  17. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

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    Yes. A bit extreme. He is nit implying a willy nilly mismatch jn any direction. Not to get into all this again but my old Mesa manual showed examples of safe mismatches ie - 16 ohm from 8 ohm jack.
     
  18. mcblink

    mcblink Well-Known Member

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    Thanks dudes!
     
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  19. Cadorman

    Cadorman Well-Known Member Premium Member

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    I think you should do it.
     
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