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Phontom Power Question???

Discussion in 'Recording' started by sushifish, Dec 18, 2007.

  1. sushifish

    sushifish Guest

    Might be a stupid question...

    When using a condensor mic, should I turn my preamp to the "Mic" setting and then turn on the +48v or:

    Turn on the +48v then switch the preamp to the "Mic" setting.

    Would doing it the wrong way damage a mic? Thanx all! -matty
     
  2. Boswell

    Boswell Moderator Distinguished Member

    Without your telling us which model of pre-amp it is, it's difficult to give a definite reply. However, on most pre-amps, the 48V PP switch is independent of the mic/line source/gain switch.

    There's no way that the sequence of switch operations could affect the mic. From the point of view of reducing thumps in the output, it would be best to connect the mic to the pre-amp with the 48V PP off and the source switched to "line" (which probably just puts a 20dB pad in circuit). Then switch the 48V PP on, wait 5-10 seconds for the power to stabilise, then switch to "mic".
     
  3. TheFraz

    TheFraz Active Member

    turn the 48v off when you connect or disconnect the mic.
    this is to prevent any loud pops.
     
  4. RemyRAD

    RemyRAD Well-Known Member

    The order of what you turn on first really makes no difference. What does make a difference is to turn down or mute your control room speakers when plugging in or unplugging your microphones with phantom power on or off. The microphone will survive but your speakers may not if you're not careful.

    Phantom mistress
    Ms. Remy Ann David
     
  5. TheFraz

    TheFraz Active Member

    my first few times in a studio had me the victem of some devistatingly loud pops.
     
  6. Codemonkey

    Codemonkey Well-Known Member

    What exactly does phantom power do? I saw a DI box that required it to be switched on to power the box, but using it on a raw mike...does it just make the signal a load louder?
     
  7. bent

    bent No Bad Vibes! Well-Known Member

    First, erase from your mind any notion of 'raw' mics (I know what you meant, but let's not confuse anyone). :wink:

    There are many different mic types, the two most common are Dynamic and Condenser.

    Dynamic mics (SM57, 58, D112, etc.) operate by moving a diaphragm - a thin membrane over a wire wound ring - through a magnet, on the same mechanical principal as a typical speaker cone or pair of headphones. They, by design, ignore Phantom Power.

    Condenser mics (AT 4050, SM81, KM84, etc.) operate via a capacitance difference between two metal plates (one 'floating', one fixed), which are energized by Phantom Power. Condensers, because of this action, are typically far more sensitive than a dynamic.

    D(irect) I(njection) Boxes (Whirlwind Director, Countryman FET85, etc.) are often powered by phantom, a 9v battery, or both (by both, I mean, if you take the 9v battery out of a Countryman FET85 and similar DI's, you interrupt the circuit, rendering the box useless).
     
  8. TheFraz

    TheFraz Active Member

    the short end of it, condenser mics need 48 volts to power them. this can apply to DI boxes as well since they need to run on some power.
    almost any mic pre has a phantom power option
     
  9. Halifaxsoundguy

    Halifaxsoundguy Active Member

    I remember those feedback loops back in Recording school. I was surprised how so many people just froze up instead of jumping for the master volume.
     
  10. RemyRAD

    RemyRAD Well-Known Member

    It is called phantom power because the power is injected into the incoming microphone lines. It is injected through 2 high precision resistors so that the direct current cancels out differentially at the balanced microphone input, while being able to provide power to the microphone without the need for batteries inserted internally into the microphone. Generally phantom power is rated at +48 volts. This is particularly true of non-polarized condenser microphone capsules such as the well-known German Neumann U87 and even some inexpensive ones made by Samson. It must be supplied with 48 volts, to polarize the diaphragm. Where many of the " back electret" pre polarized condenser microphones can operate from as little as 1 1/2 to 15 volts. Just know that if the microphone says it needs 48 volts, then it needs 48 volts and not a penny less.

    Many mixers and microphone preamps come complete with internally generated phantom power, for microphones that require it. Many do not however. In which case, an external phantom power unit is required. Many electret condenser microphones require nothing more than a AA battery to function for hundreds of hours. Don't always assume that a mixer has the capabilities of delivering phantom power unless it says so. There are other types of microphones today such as active dynamics and active ribbons that also require phantom power to make its internal electronics work. These are not be confused with tube microphone technologies. Tube microphones require both a tube heater filament voltage and the higher DC plate voltage that averages between 250 and 350 volts. You won't find any of these power supplies built into any mixer as they are generally supplied as the outboard device with the tube microphone. And tube condenser microphones do not require phantom power. Ain't nothin' Phantom about that.

    Phantom engineer
    Ms. Remy Ann David
     
  11. Codemonkey

    Codemonkey Well-Known Member

    That's the kind of info that should be compiled into an extensive list available somewhere obvious as opposed to buried in a forum, repeated to every 20th user.

    Thankfully our mics are all dynamic and the mixer has 48V phantom power.

    So phantom power would be needed on an active DI box, but not on a passive one?
     
  12. bent

    bent No Bad Vibes! Well-Known Member

    You are correct, sir!
     
  13. TheFraz

    TheFraz Active Member

    Just never put it on a ribbon that does not require it.
    #1 reason why they do not give us any ribbons to record with.
     
  14. RemyRAD

    RemyRAD Well-Known Member

    A ribbon microphone makes for a wonderful low current fast blow fuse. Everybody should have at least half a dozen.

    Blown out
    Ms. Remy Ann David
     

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