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Phantom Power and When To Use It

Topics: Mixing Skills, technical By: Chris Huff July 21, 2008

PHANTOM POWER

Phantom power (labeled as +48 V on most audio equipment) is a method that sends DC voltage through microphone cables. It is best known as a power source for condenser microphones, though many active DI (direct input) boxes also use it.

Phantom power supplies are often built into mixing desks, microphone preamplifiers and similar equipment. In addition to powering the circuitry of a microphone, in traditional (DC-polarized) condenser microphones the phantom powering directly or indirectly supplies the voltage used for polarizing the microphone’s transducer element ("capsule").

Polarizing the microphone’s transducer WHAT?  What’s a Capsule?

Condenser microphones are based on an electrically-charged diaphragm/backplate assembly which forms a sound-sensitive capacitor/capsule.  This capsule stores an electrical charge.  When the element is charged, an electrical field is created in proportional size to the distance between the backplate and the diaphram.

Take a standard grocery store tub of whip cream.  Empty it and then cover it tightly in saran-wrap.  Now if you press down on the saran wrap, you are decreasing the potential energy because there is less space inside.  If you pull up on the top of the saran-wrap in the middle you are increasing the potential energy because there is more room.

The variation between the spacing (the increasing and decreasing pressures) produces the electrical signal which represents the sound detected by the condenser microphone. 

Sound To Energy

Microphones have transducers, either dynamic or condenser types (hence dynamic or condenser microphones).  A transducer changes energy from one form into another, in this case, acoustic energy into electrical energy.

Back to That Old Phantom Magic

A condenser microphone needs some means for maintaining the electrical charge / polarizing voltage.  Creating the charge on the capsule of condenser microphones can be accomplished by battery, phantom powering, and by using fixed charge materials in manufacturing.

In the case of phantom powering, the voltage supplied through the microphone cable, such as by a mixer equipped with phantom power, is equal on Pin 2 and Pin 3 of a typical balanced, XLR-type connector. For example, a 48 volt phantom source, would have Pin 2 at 48 VDC and Pin 3 at 48 VDC, both with respect to Pin 1 which is ground.

Because the voltage is exactly the same on Pin 2 and Pin 3, phantom power will have no effect on balanced dynamic microphones: no current will flow since there is no voltage difference across the output. In fact, phantom power supplies have current limiting which will prevent damage to a dynamic microphone even if it is shorted or miswired.

Phantom power can be thought of as just the right about of power where you need it.  In some sound board mixers, multiple phantom power buttons can be present for different channels.  For example, a button for channels 1-8 and one for 9-16.  Knowing what microphones require it, tells you what channels will need it.

Note: condenser microphones that are made with pre-charged metals or are battery charged may be damaged if used in conjunction with phantom power so make sure you read the instructions with the microphone.

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Filed Under: Church Audio 101, Mixing Tagged With: Mixing Skills, technical

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Comments

  1. LH2160 says

    March 26, 2018 at 8:23 pm

    “condenser microphones that are made with pre-charged metals or are battery charged may be damaged if used in conjunction with phantom power so make sure you read the instructions with the microphone.”
    What kind of damage?

    Reply
    • Chris Huff says

      March 29, 2018 at 11:20 am

      The kind that stops the microphone form working correctly.

      Reply
  2. Jireh says

    January 4, 2018 at 12:02 pm

    i have a question
    for a mixer with a phantom power supply, is the phantom power (+48v supply) only present in the xlr input? is it not present with the PL input also?

    Reply
    • Chris Huff says

      January 7, 2018 at 6:35 pm

      that should be correct but check the manual.

      Reply
  3. Carrie-Lyn SNIDE says

    November 10, 2016 at 7:53 am

    Question, at my church we have a mic that I believe needs phantom power, i hink its a drum mic. we have no instructions for the mic. Phantom power would be applied at the mixing console. Is there a possibility of damaging the other mics and instruments if we press that button for only the one mic?

    Reply
    • Chris Huff says

      November 11, 2016 at 10:09 am

      No, phantom power will not damage mic’s that don’t need it.

      Reply
      • Jeffr Sellers says

        February 26, 2017 at 3:14 pm

        What about other gear in the board…acoustic electric, digital piano, keyboards? Could Phantom Power damage those? They are all on passive DI boxes right now because I wasn’t sure how Phantom Power would affect them. Thanks!

        Reply
  4. Howard Spence says

    February 15, 2014 at 1:46 am

    Regarding the whipped cream tub analogy: When you press down on the saran wrap, you are doing work, and thus increasing the potential energy. Similarly, when you pull up on the saran wrap, you also do work, and increase the potential energy. Potential energy is the lowest when the saran wrap is flat. Just like a spring. You can pull or push on the spring, and in both cases, the potential energy increases. Release the spring and it returns to its lowest potential energy state, which is its normal un-deformed length. Same in a microphone. The compression and expansion of the diaphram each will produce a different voltage polarity, giving rise to an AC signal, but the negative peak and the positive peak both represent high potential energy states.

    Reply
  5. @elishalyx says

    August 2, 2012 at 7:16 pm

    “@churchsoundguy: Phantom Power and when to use it: http://t.co/18pJr79n” @ChngJJ

    Reply
  6. David McLain (@churchsoundguy) says

    August 2, 2012 at 1:24 pm

    Phantom Power and when to use it: http://t.co/dZGp5iMw

    Reply
  7. victor says

    February 21, 2012 at 10:57 pm

    huh?…lol

    Reply

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