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condenser mic - rewire/convert 1/8" to XLR?

Discussion in 'Electronic Basics' started by Mad Scientist Jr, Jun 22, 2007.

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  1. I have a couple of electret condenser mics (Radio Shack Cat. No.
    33-1060 or similar) that run off a AAA battery and have a 1/8" plug.
    Is it possible to rewire these to accept XLR cables instead for
    increased signal strength? How?
    Thanks...
     
  2. Keith Adams

    Keith Adams Guest

    An XLR plug will only make a balanced signal and more clarity but not
    hotter. You need to have a 3 conductor cord coming from the mic.
    If it has that then yes .Just wire up the plug. You need to make sure which
    pin is hot and put a jumper from the body ground on the XLR plug to the
    ground wire pin on it as well. The body ground is the screw that tightens
    the plug end to the metal body. The plastic solderless type are a bit
    different but you can figure it out when you get inside it.
    If your mic now has a 1/4" jack on it then its probably 2 conductor and
    I've put un needed miles on my typing finger for nothing.
     
  3. Thanks for your reply.

    I'm not sure how many conductors it has, I think it has 2 hot and 2
    ground, but I will have to open it up to make sure.

    Let me clarify my question though - say you have the following circuit
    -

    http://www.electronicsteacher.com/circuits-and-diagrams/audio-preamp-circuits/preamp.gif

    with a microphone attached. What modifications would you do to *make*
    it a 3-conductor connection for XLR? Because I am also building some
    microphones with that preamp circuit and would like them to have XLR
    connectors.

    Thanks again...
     
  4. sycochkn

    sycochkn Guest

    Transformer.
     
  5. Thanks for the reply - what kind of transformer? How do you wire it
    up? Is there a good schematic online how to do this?
     
  6. sycochkn

    sycochkn Guest

    High impedence to low impedence microphone transformer. It will probably
    have a 1/4 input and and XLR output. or you could get a seperate transformer
    and mount it in your preamp.

    Bob
     
  7. Keith Adams

    Keith Adams Guest

    You cant get more signal strength from the mic element.
    Only from the preamp. You should actually give up on your current plan and
    buy some better mics. An electret mic element due to its being active
    usually puts out a very hot signal by its self. Along the lines of -35db. A
    very very hot dynamic or crystal will only produce a measly -50db in
    comparisson. A dynamic at -50db hooked to a high impedence transformer and
    into a guitar amp will overdrive the holy hell out of it even at low volume.
    High volume and the amp will go into run away feedback. If your mics are
    presently using a 1/4" plug on the end of the cord then they're more than
    likely 2 conductor and toy microphones. If you want an XLR plug on them
    there will be no improvement in the mics performance but buy an adaptor for
    1/4" to XLR. I really think you need to do more research on the subject
    though.
     
  8. Keith Adams

    Keith Adams Guest

    What is it exactly that you want to accomplish besides having an XLR plug
    on your mics? Are you by chance trying to make a hot harp mic?
     
  9. tempus fugit

    tempus fugit Guest

    I'd just use these:

    http://karmaaudio.com/kmicro.html

    For $10 apiece, you cant really go wrong - it's all wired up for you and the
    XLR is already there..
     
  10. David Martel

    David Martel Guest

    Mad,

    There's a fellow named Forrest Mims III who is quite famous for his
    ability to write readable introductions to various sub-specialties of
    electronics. Radio Shack used to sell some of his audio books. Your local
    library should also have his books.
    As others have said, rewiring your cable for an xlr plug will not
    increase your signal strength. By putting a transformer in line with your
    mic output you can convert from unbalanced high impedance to balanced low
    impedance. It's not clear why you want to do this.
    If you want to learn electronics perhaps the local tech school has a
    course or two. Book learning will not help you when you need to use a
    soldering iron and punch or drill holes

    Dave M.
     
  11. Thanks for your reply. This mic isn't going into a guitar amp, it
    would go into a mixing board for recording.
     
  12. An inexpensive way to make/modify some nice sensitive condenser mics
    to record with.
     
  13. Pretty cool - btw what is the difference between buying a matched pair
    and just buying two of the same mic?
    Thanks for the link!
     
  14. PS this would be for omnidirectional mics, so those $10 xlr mics from
    karmaaudio probably wouldn't work for replacing these. If it's
    possible to wire them to XLR without too much trouble or cost then I
    would just like to try it. A mic going into an XLR input has more dB
    than a mic going into a 1/4" input.
     
  15. Eeyore

    Eeyore Guest

    It won't affect their 'signal strength'.

    Graham
     
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