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Two mics in one jack

Discussion in 'Sound, Music, and Intercom' started by Capi, Nov 16, 2005.

  1. Capi

    Capi Member

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    I'm curious if it's possible, via some sort of of y-adapter or something, to plug two hand mics into one jack on stage. They would obviously both be on one channel on the board. Is it possible?
     
  2. AVGuyAndy

    AVGuyAndy Active Member

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    Yes.
     
  3. Capi

    Capi Member

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    Where would I get such an adapter? Would Rat Shack have one? And what would you call it?

    Thanks a lot.
     
  4. AVGuyAndy

    AVGuyAndy Active Member

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    I would just make my own. You are looking for a Y-adapter.
     
  5. sound_nerd

    sound_nerd Active Member

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    That's a mess waiting to happen....It's much harder to control two mics from one channel that you'd think. Plus, I doubt the pre-amp is meant to handle that...
     
  6. AVGuyAndy

    AVGuyAndy Active Member

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    The Greatful Dead used to have a crazy adapter which would wire all their tom mics in parallel. The pre-amp can handle it fine.
     
  7. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    I would expect that they would have used an external mixer or some form of a summing amp to combine the signal.

    Y-leads can cause problems when they are being used in this manner as signal coming in from one mic can travel into the other mic and vice versa. There will also be some signal cancellation as well

    This is why a summing amp or resistor snub circuit is used when converting a true stereo signal into mono one.

    Simple experiment. Take 2 CD players and run the outputs into a Y-lead and then into your desk. Now, whilst music is playing, unplug one of the 2 CD outputs. Notice what happens to the sound?
     
  8. JahJahwarrior

    JahJahwarrior Active Member

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    Mayhem--I don't know much about electronics, but what if on every lead in the cable you wired a diode? I don't know exactly where, but if you did that, then it would prevent the electricity from traveling bck up the mic lead....
     
  9. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Audio signals are AC so a diode would not work. Depending on which way you wire in the diode as to whether you would drop the positive or negative deflection of the sine wave.
     
  10. JahJahwarrior

    JahJahwarrior Active Member

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    oh, that's right....
     
  11. BillESC

    BillESC Well-Known Member Premium Member

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    Simple

    [​IMG]

    For even more control

    [​IMG]
     
  12. Capi

    Capi Member

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    Cool. Thanks.
     
  13. Scooter

    Scooter Member

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    it is very possible. sometimes when doing gigs with a smaller board, channel space becomes a big issue. so i soldered my own adapter to run two rack tom mics into one channel. works like a charm every time!
     
  14. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    How did you make the adaptor?

    Whilst it might work like a charm, it may still cause damage.

    I have/had the schematic for a simple resistor network for summing two signals. I also have the schematics for a summing amplifier as well, which is active and therefore does not cause any signal loss, like the resistor network will.

    If anyone wants them, let me know.
     
  15. Scooter

    Scooter Member

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    i just soldered the leads together (1 to 1, 2 to 2, etc.) and then soldered them to the xlr jack.

    i wouldn't mind havin a look at those schematics though
     
  16. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Ah! the classic Y-Lead. Has the potential to cause damage to your equimpent and I will have a look for those schemaits for you. The resistor network should fit into the XLR.
     
  17. Inaki2

    Inaki2 Active Member

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    I actually saw this in use in a Boston Pops show, all their SM81s were dualed at the sub-snakes.

    The preamps can take it as long as the impedance doesn't drop low enough to start "shorting" out.
     
  18. Andy_Leviss

    Andy_Leviss Active Member Premium Member

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    Scoter,
    DO NOT DO THIS

    To directly connect two outputs together into the same input is dangerous, and can damage equipment. For details, check out this tech note from Rane: http://www.prosoundweb.com/studyhall/rane/wye/wye.php

    If you must do this, use a combiner like the above box or the circuit shown on the page I linked to to do it safely.

    --A
     
  19. Radman

    Radman Well-Known Member

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    Great link!
     
  20. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    The circuit shown in the link provided by Andy is the same as the one that I have. The active summing amp one is on the way once I find my note book that has it in there.
     

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