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Phantom Power?

Discussion in 'Amps and Cabs [BG]' started by Quadzilla, Mar 6, 2005.


  1. Quadzilla

    Quadzilla Supporting Member

    All-

    This is the closest forum here that I could post this in. I just got a new mixing board and it has a switch for "phantom power". What is this and what is it used for?

    Thanks much!
     
  2. http://www.sounddevices.com/tech/phantom.htm

    "Phantom powering" is a method of providing power to microphones by applying a voltage to the same wires that carry the audio signals. Phantom power can be generated from mixing consoles, mic preamplifiers, or in-line phantom power supplies. All of Sound Devices microphone inputs supply phantom power.

    In general, phantom voltages are used to power electronics within condenser microphones. Condenser microphones require power for various parts of their operation, including impedance converters, preamplifier circuitry and, in some cases, to polarized microphone capsules. Phantom is usually a DC voltage ranging from 12 to 48 volts. Microphones draw current from this voltage based on their needs.

    Balanced microphone interconnections have two signal conductors relative to a ground conductor. With XLR-3 connectors, pin-2 and pin-3 are the signal conductors and pin-1 is the ground conductor. The definition of phantom power is an equal voltage applied to pin-2 and pin-3 with respect to pin-1. To verify that a mixer or preamplifier provides phantom power, voltage measurements taken between pin-2 and pin-1, and pin-3 and pin-1 will read identical levels. No voltage is present between pin-2 and pin-3. Popular phantom voltages are 12 V, 15 V, 18 V, 24 V, and 48 V. 48 volt phantom is the most common and many microphones require 48 V for proper operation. New specifications from the AES outline five specifications for phantom voltages and current levels - P12L, P12, P24, P48, and P48H.

    Because phantom voltage is exactly the same on pin-2 and pin-3 with respect to pin-1, phantom power has no effect on balanced, dynamic microphones. A properly connected balanced, dynamic microphone will operate with or without phantom present. With ribbon microphones turning phantom power off is recommended.
     
  3. Folmeister

    Folmeister Knowledge is Good - Emile Faber Supporting Member

    May 7, 2003
    Tomball, Texas
    Unless called for, leave it off. And, only turn it on or off with all gains turned to 0.
     
  4. DubDubs

    DubDubs

    Aug 23, 2004
    Los Angeles
    It's for condenser mics. Make sure it's off if you're running D.I into the board. I've heard stories of ruined D.Is from Phantom Power.
     
  5. Quadzilla

    Quadzilla Supporting Member

    :)
     
  6. thejohnkim

    thejohnkim

    Sep 30, 2003
    NYC
    yeah, DIs are tricky though. some DIs get ruined by phantom power (i.e. early SWR stuff), while others can be powered by phantom power so you dont need to plug them in to an outlet (i.e. SA BDDI)
     
  7. I would say, that with my EBS head, Phantom power is there, So, I just ahev to plug a pedal, or my active bass in it, and I don't have to put a battery on one of both...
    That's nice, but you need a stereo cable (I suppose that name in English!), but that's not a common cable...

    Vince
     
  8. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Most of the better DIs are immune to phantom power or, as others have said, use it for their active electronics.
     
  9. SWR states the DI on their various heads and preamps will be damaged by phantom power.

    This becomes a real issue when phantom is globally switched, i.e. turning it on affects every channel on the mixer. The better mixers have individual phantom power on each channel.

    My Countryman Type 85 DI box loves phantom power, but only at the standard +48 volts. If you have a DI built into your preamp or head, consider using a separate DI box, such as the Countryman, to prevent a clod sound man from destroying your amp with phantom power. I own an SWR IOD and carry the Countryman for this reason.

    If phantom is present, *always* ask the sound man before disconnecting or connecting. He will drop phantom so you can make your connections.
     
  10. nastyn8c

    nastyn8c

    Feb 7, 2005
    Tampa, FL
    where do you buy this so-called "countryman," and for how much? I run an SWR SM-400S into a PA with somewhat dumb sound guys.
     
  11. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
  12. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    I get mine at NSL, too. Those guys rule. The Countryman Type 85 rules, as well. Just the pure, unadulterated tone of your bass. As an extra added bonus, they are virtually indestructable. Seriously, you could run over one with a truck and not hurt it at all.
     
  13. There are some interesting caveats with the Countryman... for starters, it is wired phase-backwards. Next, it really HATES phantom power less than standard +48v.

    I tried running it with a Rane preamp with +15v phantom and it is awful. If you try to do this, Countryman requires you remove the 9v battery first. You can leave the battery in place when running +48v phantom.

    The Countryman is excellent for passive basses, and (reputed) to be much less so for active ones. JTurner owns one, and made this comment.. I have not run my active L1500 through the Countryman, so cannot comment.

    As Munji pointed out above, it passes just the sound of your bass. Tone, warts, and all. Very nice DI, IMO.