Phantom power

Phantom power is a 48V DC voltage sent up an XLR cable from an audio interface or mixer to power the internal electronics of a condenser microphone. The name comes from the fact that the voltage travels invisibly on the same wires that carry the audio signal, without needing a separate power cable to the mic.

Dynamic microphones do not need phantom power to operate, since they generate their own small signal mechanically, but most dynamic mics are unharmed if phantom power happens to be on. Ribbon microphones are the main exception, since some older or unbalanced ribbon designs can be damaged by phantom power, so checking the manufacturer's guidance matters there.

On most interfaces and mixers, phantom power is a switch labeled 48V that applies to one channel or a group of channels at once. It should generally be switched on before plugging in a condenser mic and left on for the session, since some interfaces produce a brief pop when phantom power is toggled with a mic already connected.