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Vintage Crystal Mic seeks use

Discussion in 'Pro Audio Equipment' started by patrick_like_static, Jul 26, 2007.

  1. I recently came across a Midland 22-104 Dual Crystal Microphone and I'd like to see how it sounds as an effect mic. Can anyone tell me how I could rig this up to use for recording? Obviously the 4-pin female plug (CB style, shown in picture) will need to be XLR male, but how do I go about doing this?

    Given that it's a crystal mic, will I need some kind of transformer before the new plug? What of the push-button device attached to the cable (also shown)?

    Thanks in advance. I'll appreciate any help I can get.

    http://img521.imageshack.us/img521/9162/midland22104yu3.jpg
    http://img521.imageshack.us/img521/2134/midlandcablekz8.jpg
     
  2. Boswell

    Boswell Moderator Distinguished Member

    You would be OK running this into almost any interface or pre-amp fitted with an instrument (guitar pickup) input. Make up a screened cable with a 1/4 inch TS jack on one end and then experiment with the wiring to a 4-pin CB mic plug.

    The 4-pin plugs are available from almost any CB shop (breakers' yard), or online from places like Nevada Radio. Bizarrely, the Nevada site has the plug pictured and listed as MIC F317, but calls it a socket. Must be CB-speak.
     
  3. Thanks, Boswell. Do you know of any way to circumvent the switch, so that the microphone is constantly "on?" Ideally, I'd like to make a brand new cable because I'm uncertain about the amount of wear on this one.

    Would it work to simply cut off the cable before the switch and attach a T/S cable?
     
  4. Thomas W. Bethel

    Thomas W. Bethel Well-Known Member

    In most cases the switch "keys" the transmitter (turns it on) and it is nothing more than a normally open switch. Two of the contacts on the 4 contact plug are wires connected to the switch. The other two connectors are shielded and go from the microphone to the input of the microphone preamp on the CB transceiver. If you don't mind cutting the cable then you can just hook up the shielded wire to a 1/4" phone plug (inner conductor to the tip - shield to the sleeve) and just tape up the other two wires.

    Crystal microphones are very high impedance and should be plugged into an instrument input for best results OR you can get a 50K to 150 ohm transformer (hiZ to lowZ) and plug the microphone into a normal microphone XLR input.

    Hope this helps.....
     

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