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I have a Yamama analogue mixer which has a phantom power switch (it turns phantom power on for all channels).

We have a few condenser mics that need phantom power as well as a handful of wireless mics, DIs, etc. Would leaving phantom power on hurt the wireless mics or cause any interference with the wireless mics? Or is it best to get a few separate Phantom Power Supply units?

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    Great question. I've wondered this from time to time but never actually spent the time to give it a proper thought. Removing the 48V (DC) at the mic is as easy as placing a capacitor in series, so my best guess is that no reputable manufacturer would try to save money by not placing it and risking its mic to be fried by such a common mistake as leaving phantom on. – Schizomorph Nov 13 '17 at 16:10
  • @Schizomorph that'd be true nowadays. But get yourself a vintage ribbon mic, and you need to be careful. Phantom WILL tear the ribbon. New ribbons usually do have that protection though. – user22688 Nov 13 '17 at 19:10
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How about checking the manuals for your wireless mics (or more likely their receivers)? It's unlikely that they'd be unprepared to deal with phantom power, but naturally nobody can make any guarantees apart from the manufacturer. It's easy to build input circuits with capacitors that won't stand for 48V, but it would also be imprudent.

  • I'll have to dig around for the manuals! Thanks for the suggestion @user23366 :) – lrey1 Nov 13 '17 at 21:51
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Transformer balanced devices such as dynamic microphones and passive DI boxes are usually OK with phantom power being present even if they don't need it. Anything that is not definitely transformer balanced should not be connected unless it is explicitly specified to be connected to phantom power.

Your wireless receivers, which, if they have balanced outputs, are almost certainly active balanced, should not be connected to phantom.

But there is a solution: The Yamaha mixer puts phantom only on its Mic (XLR) inputs, not on the Line (1/4 inch TRS) inputs. So, if your receivers have line level outputs, use those and connect using 1/4 inch and you'll be all set. If your receivers offer only mic level output, then the other option you have is to use a 1:1 transformer isolation box such as the ART DTI or Whirlwind ISO-2, connected between the receivers and the mixer. One isolation box can handle two mic channels.

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