Q: Why does my mixer have a 48 volt switch?

  A RecordProducer.com reader wonders what the phantom power switch is for, and how it might improve the signal from the microphones.

By David Mellor, Course Director of Audio Masterclass

A question from a RecordProducer.com reader...

"My mixer has a phantom switch that sends +48  volts DC to the microphones when switched on. May I know what is the real purpose of this phantom switch & how does it improve the sound signals coming from the mics to the mixer?"

Phantom power is available on mixing consoles, microphone preamplifiers and the microphone inputs of audio interfaces to power capacitor microphones and DI boxes.

To put it simply, if you want to use a capacitor microphone or powered DI box, phantom power must be switched on.

The exception to this is if you are using a capacitor microphone that has its own dedicated power supply. This applies to very old capacitor microphones and some modern capacitor microphones that emulate this retro style.

Some mixing consoles do not have phantom power switching. Some have one switch for the whole console; others have one switch per channel.

In theory any professional microphone that does not require phantom power should not be affected by it either physically or sonically. It is worth noting however that ribbon microphones can, under certain circumstances be damaged when connected to a phantom powered input.

Connecting anything other than a microphone or DI box to a microphone input is generally an act of folly and damage may or may not ensue due to the presence of phantom power.

In summary, phantom power does not improve the signal in any way; it allows capacitor microphones and powered DI boxes to function.

Publication date: Friday April 15, 2011
Author: David Mellor, Course Director of Audio Masterclass