What is 48V Phantom Power? Phantom power refers to the power source used by audio devices in order to replicate the effect of microphones. Although the ANSI standard recommends a voltage of between 11 and 52 volts for phantom power, most studios prefer 48 v. When you buy an audio interface, you will usually find a +48v button near the XLR connector inputs. Standalone preamps usually have this button, too, but you rarely need to use one.