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How Phantom Power Works

Many podium mics are condensors, and as such need power. Problem is you need it to use the same XLR cabling as dynamic mics. Phantom power to the rescue.

Phantom power is DC power that is run down the audio lines to the microphone, where it is tapped off to power the mic. The de factor standard is 48 volts, but I've seen phantom voltage as low as 9 volts. Many mics can take a wide range of voltage, but not all, so it is best to check. When phantom power is on, as it is all the time with many permanently installed sound systems), it makes that loud pop when you plug or unplug.

The secret to not messing up the audio is to apply it to both audio connections equally. The mic input is balanced, and measures the difference between the two audio connections, which in this case would be zero. DC blocking capacitors in your board (or transformers in older boards) prevent the 48 volts from blowing up the chips.

On the mic side the DC is siphoned off to power the small preamp inside the mic that raises the incredibly low signal coming off the capsule into just fairly low level mic signal you need. That's why with a Condensor mic a presenter (or singer for that matter) can overload the mic itself, even if their not overloading the board.

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Here's a pdf of an article I wrote for Audio Media Magazine
"Interfacing with Inexperienced Clients"

About the Owner
photo of Lonnie Bedell of AVlifesavers.com My name is Lonnie Bedell, and I'm the guy behind AVLifesavers. Unlike big companies, I've been doing actual live sound work since 1995, and live recordings since 1985.
It's that kind of real world experience that I feel makes AVLifesavers stand out. It's one thing to examine problems theoretically, it's a whole different thing to deal with frantic last minute changes from an inexperienced client who wants it done yesterday.

Been there, done that, so I've designed products to solve live sound problem fast.

All products are assembled right here in the USA. Living Wages to American workers is and will always be part of the fabric here, despite the temptations.

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