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  • Phantom power and passive mixers

    I am not new to working sound, but I am relatively new to using condenser mics for live sound. I understand the need for phantom power with condenser mics and have no trouble when using a powered mixer since that option is offered by the mixer. However, when using a passive analog mixer with a separate power amp I have some questions.

    Do any passive mixers have the phantom power option, or do you need a separate phantom power unit for each condenser mic you are using? I see online that there are multi channel phantom power units available; is that what is recommended when using multiple condenser mics?

    Thanks in advance for your thoughts.

    One_Dude
    I've had enough of folks who don't know what they want, but are very good at knowing what they don't want.

  • #2
    It has been my experience that most mixers do have Phantom power. Usually it's "global" (all channels) such as on an A&H Mixwizard. It has been my experience that global phantom power on does not affect standard (non-phantom-powered) wired mics.....at least not in all of my applications to present.

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    • #3
      Correct, phantom power does not affect dynamic mics but can ruin most ribbon mics. I've not encountered a passive mixer yet that did not have phantom power but I'm sure they exist.

      A&H GL2800 console, BagEnd Crystals over D-18's, 12"and 15" BagEnd and EAW wedges powered and processed by QSC, Klark, BSS, Symetrix, Valley, Sabine, Peavey and BagEnd INFRA.

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      • #4
        Originally posted by Mike M View Post
        It has been my experience that most mixers do have Phantom power. Usually it's "global" (all channels) such as on an A&H Mixwizard. It has been my experience that global phantom power on does not affect standard (non-phantom-powered) wired mics.....at least not in all of my applications to present.
        Just for accuracy - on my Mixwiz (3), phantom power is switchable for each of the 16 XLR inputs.

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        • #5
          Just to get the terminology straight, "passive mixer" is not what we're talking about here. Nearly all mic mixers have mic preamps in them which are active devices. A truly passive mixer is a series of resistors and/or transformers which isolate the inputs but add no gain (but always loose some in the translation). These are few and far between and only used in very specialized applications.

          OK Back to your question: Almost every mic mixer made today has phantom power available.

          Although most condenser mics are very forgiving, some require a full 48 Volts and a fair amount of Current to operate (some cheaper mixers fall short with these specs). Lower dollar mixers make it available either globally or in groups (I.E. 1 thru 4 & 5 thru 8.........). Switches cost money. Higher priced mixers have a switch for each channel.

          The reasons for wanting individually switched phantom power are:
          1) An iffy connections in your mic lines or snake can cause major pops when phantom power is supplied (even an intermittent ground which could otherwise go unnoticed will pop or crackle loudly if phantom power is present).
          2) if you were to input a submixer (think several keyboards OR a separate DJ mixer) into inputs with phantom power on it, you risk damaging the upstream submixer's outputs.

          It is true that phantom doesn't hurt most moving coil dynamic mics because they have an isolation/impedance matching transformer built in. This is true for most all mics of this type. It's also true that phantom power will KILL most ribbon mics (also considered dynamic mics - but this is splitting hairs) but there are exceptions (some newer ribbon microphones have active impedance matched preamps built in and actually NEED phantom power to work - Check the manufacturers recommendation). You probably won't run into many ribbon mics as they are somewhat fragile and are not used in sound reinforcement often.

          Hope this helps
          Last edited by Dogoth; 10-30-2016, 11:08 PM. Reason: Typo
          J.R. Previously jrble

          See my Dog Of The Hair studio at: http://www.dogoth.com/studio/

          Quote from someone: Flat response? Get out the jack and change the tire.
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          • #6
            Similar to #2 above, many keyboards have XLR outputs now, which will tolerate phantom power but really shouldn't be sent it if possible. Also, depending on your keys rig, it's possible for the phantom power toggle pop to get fed into your keys player's monitor, which is not ideal.

            The best solution to ensuring certain parts of your system do not get phantom power is an XLR-XLR isolation transformer. Thirty bucks.

            Wes
            Do daemons dream of electric sleep()?

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            • #7
              Originally posted by loco_p_man View Post

              Just for accuracy - on my Mixwiz (3), phantom power is switchable for each of the 16 XLR inputs.
              oops, my bad. The phantom power is global on my Yamaha MX12/4 mixer....

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