Denver Recording Studio

Phantom power refers to the method of sending 48v DC (or, in certain situation, 12v or 24v) through a microphone (XLR) cable.  This is necessary to power condenser mics, as well as some DI boxes.   This feature is built into most preamps and mixing desks.  Phantom power made possible the use of the same shielded, balanced cables used with dynamic mics for condensor mics.

Condensor mics require phantom power because they contain active electronic circuitry.  This circuitry requires voltage in order to operate.  This voltage also powers the polarization of a condensor mic’s transducer element. 

A word a warning: never send phantom power through a ribbon microphone.  While this type of microphone is becoming increasingly rare, should you encounter one, understand that the internal nanofilm ribbon can catch fire if phantom power is applied.  Since ribbon mics do not contain active electronic circuitry, they do not require phantom power to function.