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15797Re: [nwbluegrass] Phantom Power requirements

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  • Mark Gensman
    Feb 1, 2004
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      eddard, you are correct. Most mics that require phantom power have a
      regulating circuit that takes from 9 to 50 volts and converts it into the
      proper voltage to charge the mic properly.

      Since the line loss of voltage is very small, and most mixers put out more
      than the nine volt minimum requirement, 100 foot mic cord lengths are not
      going to cause any significant voltage loss. Checking the voltage resistance
      of 22 or 24 guage stranded wire, which is what mosts mic cords and snakes
      use, you would find the voltage drop in a hundred feet to be very little,
      especially if you started with 15 volts and only needed 9.

      Certainly you can buy components and build your own phantom power supplies,
      however, when you can buy phantom power units for under $40 you would be
      hard pressed to build something better for anywhere near that cost.

      Final point, if a non phantom powered balanced dynamic mic puts out enough
      level to drive a signal through a 100 foot mic cord, certainly phantom power
      will make the trip with very little loss..

      Mark Gensman
      Ground Zero Sound


      >From: "eddard" <eddard@...>
      ---SNIP--->
      >Well, I too am ignorant, but I have wondered why my Rode NT-3's will work
      >on
      >either 48v phantom power or a 9v battery. My best guess is that the
      >internal circuitry of the mic regulates the voltage actually used by the
      >mic
      >to less than 9v, in much the same way that most of the oil pumped by the
      >pump in an oil furnace with a 2-pipe system returns to the tank and only a
      >small portion of it goees to the burner's nozzle.
      >
      >The reason for using 48v from the mixer board would, if that analogy is
      >correct, be to assure that the resistance in the microphone's long and
      >possibly small cord would not cause a voltage drop such that there wouldn't
      >be even 9v available at the mic, because the cord had expended too much
      >voltage in the length of its run.
      >
      ----SNIP---

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