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How to Wire up a balanced Mic

Discussion in 'Pro Audio Equipment' started by leachim, Sep 26, 2004.

  1. leachim

    leachim Guest

    Hi

    I have an old Sony Condenser mic with a battery. I think it came with a stereo jack. I changed it to an xlr.

    I am wondering if I wired it up right.

    I have blown the fuse and knackered some components to do with the 48v phantom supply on my mixing desk - I have since suspected some dodgy xlr cables which I have chucked, but don't want to knacker the desk again with this Sony mic.

    Because the Sony mic has a battery of its own - it shouldn't need a 48v supply should it ?

    It has 3 wires coming from it, one being the ground.

    How should it be wired ?

    Thanks

    Mike
     
  2. ghellquist

    ghellquist Member

    Hmmm.

    Not quite safe to make guesses here, but I will do them anyway.
    Perhaps if there is some kind of number or name on the mic it might help.

    First, "old Sony condensor" with a 1.5 V battery, and three wires coming out. My associations are as follows:

    - with a 1.5 V battery -- this is an electret mic (nothing wrong with that). It will not need 48 V phantom, and might as well burn up if you applied it. So start the testing using a mic preamp or whatever where you are sure there is no phantom.
    - three wires, old Sony.. hmm. Could it be that this is actually a stereo mic? Is there a switch label off/90/120 then it is definitely a stereo mic. The 90/120 setting is for different "widht" in the stereo image.
    - is it balanced or unbalanced? Well, if it is stereo it sure is unbalanced (otherwise there should be minimum 5 wires).

    Suggestion. Assume it is a stereo mic. Get 2 XLR connectors, do some soldering.

    Ground goes to in 1 AND 2 on both XLR-s. (Yes both, we are making a reference voltage here, the poor mans alternative to a unbalanced to balanced transformer).
    Pin 3 on each of the two XLR-s takes one each of the two signal wires.

    Now, test.

    Assuming you get a stereo signal, all is clear.

    But if you get the same signal, one of them should be inverted (quick test, mono sum them). And then you have a balanced signal, so move over to one XLR. Pin 1 (middle pin) is ground, pin 2 and 3 the two signal pins.

    Good luck.
     
  3. leachim

    leachim Guest

    Hey, thanks for getting back to me

    It actually uses a 9v battery, is not stereo.

    On the vocal side of the mic it has a slider with 3 positions - OFF - MUSIC - VOCAL.

    Only other thing written on the outside seems to be "BE"

    Inside it has a serial number 16114 - also a Pad switch for 0db and -8db

    Hope this helps

    Mike
     
  4. Kurt Foster

    Kurt Foster Distinguished Member

    If it came with a 3 conductor mini or 1/4" plug I assume it is a stereo mic ... Can you look to see if it has 2 elements?
     
  5. ghellquist

    ghellquist Member

    HI Mike,
    this mic does not fit anything I have ever seen. I would try it as a balanced electret mic. This means that you should protect it from phantom power, it will not need it, and could possibly be destroyed by it.

    So connect it to the XLR connector.
    Pin 1 - (the one in the "middle, but they are marked) to ground
    Pin 2 - one signal
    Pin 3 - the other signal.

    If you have Phantom off, I cannot see how you could destroy your mixer or mic, so try it. The setting Music / Vocal could be adding a high-pass filter (or low-cut) in the Vocal position. The setting -8dB on a pad is a bit odd, but what do I know.

    Next simply try the mic, you might like it or not, you really never know. Most often though, I have been disappointed. If you really like it, then it might be worth investing a bit to get a "phantom-free" input. There are a number of ways, but come back once you have tried.

    Gunnar.
     
  6. leachim

    leachim Guest

    Ha !

    Just found the type of mic

    ECM-56F

    Electret Condenser Mic from the late 70's

    3 wires come from it - one being ground

    Does anyone have any info on this one and how it should be wired on an xlr plug. Can it be powered by phantom power ? It has a 9v battery compartment.

    The phantom power cannot be switched off on my desk. As the fuse is blown for it, I can use this mic quite well on the xlr input. But I have other mics that require P power.

    However, when I get the phantom power fixed, I don't want this mic to blow up the phantom power again (if it did in the first place ?)

    Thanks

    Mike
     
  7. ghellquist

    ghellquist Member

    Hi Mike.

    Here is a specification sheet.

    http://www.danalexanderaudio.com/othermic.html#SonyECM56

    According to that it can be used both with internal 9V battery or with standard phantom power (and it says their phantom power is 49V). So you should be all go with the connection given in last mail.

    Good luck

    Gunnar
     
  8. leachim

    leachim Guest

    Wicked !

    Thats the one

    However, go to

    http://www1.jaycar.com.au/images_uploaded/plugnxlr.pdf

    and check out the xlr connections - I am not sure from a previous post if some connections are muddled.....

    On mine, the "hot" pin on the xlr male is connected to the black wire from the mic

    The "cold" pin on the male xlr is connected to the red wire from the mic. (The cable is soldered to the mic)

    I am wondering if the red wire should be to the hot pin. However, the mic works through the desk without phantom power (with battery)

    In the description it say that it can be used with both phantom AND battery - there is no switch to determine either - is it automatic ?

    Are we getting closer ?

    Cheers

    Mike
     
  9. ghellquist

    ghellquist Member

    Hi Mike,
    You are right. I wrote "the one in the middle" on the wrong pin. Your reference is right on that one, and they are marked. Generally, I would connect red to hot and black to cold. It does make a difference, especially when you use more than one mic, but it is not that important. Fix it if you want to. Otherwise the board probably has an invert button.

    Automatic switching between battery and phantom is very simple to implement. It is probably only a single diode that is added to make it "automatic", so that is probably what there is. The important thing is for the mic to be protected against the 48V and that only takes two capacitors.

    Gunnar.
     

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