Phantom power is a 48 volt DC supply sent from a mixer or audio interface down a microphone cable to power the microphone. It is the reason condenser microphones work with ordinary XLR cables, and the +48V switch on your gear is how you turn it on.
What it is for
Condenser microphones have a charged capsule and internal electronics that need power, which dynamic microphones do not. Phantom power supplies that power through the same cable that carries the audio, so you do not need a separate power cord or batteries. Some active DI boxes and other gear use it too.
How it works
The 48 volts are sent equally down the two signal conductors of the XLR cable (pins 2 and 3), with pin 1, the shield, as the return path. Because the voltage is the same on both signal pins, a balanced microphone input ignores it, and the audio is not affected. That is why it is called phantom: it travels in the cable without being part of the signal. This relies on balanced connections, covered in balanced vs unbalanced audio.
Using it safely
- Connect the microphone first. Plug in the cable and microphone, then switch phantom power on.
- Turn the channel volume down or mute the channel before switching phantom power on or off. A loud thump through the speakers can occur otherwise.
- Switch it off before unplugging. Turn phantom off, wait a moment, then unplug.
- Use a properly wired balanced XLR cable. Damaged or miswired cables are the main cause of trouble.
Which microphones need it?
| Microphone type | Phantom power |
|---|---|
| Condenser (most studio mics) | Usually required, unless the mic runs on batteries or an external supply |
| Dynamic | Not needed. Generally unaffected by it when the cable is wired correctly |
| Ribbon | Not needed, and some older or delicate ones can be damaged. Check the manual before switching it on |
| USB | Powered by USB, so phantom power is not used |
Common questions
Will phantom power damage a dynamic microphone? Not normally. A dynamic mic on a balanced, correctly wired cable sees the same voltage on both signal pins, so no current flows through it. If you are unsure, turn phantom power off.
Can I use phantom power with a 1/4 inch TRS cable? It is not designed for that. Phantom power is part of the XLR microphone input standard, and a line input does not provide it.
Why is there no phantom power on some inputs? On some gear it is switched for groups of channels and on other gear per channel. Check the manual for which inputs the switch affects. If a condenser mic is silent, check the switch first.
Condenser or dynamic?
If you are choosing a microphone, a dynamic one is simpler, does not need phantom power, and handles loud sources and noisy rooms well. A condenser captures more detail but needs phantom power and a quieter room. See XLR vs TRS vs TS for the cable you need.