48V. Phantom Power. What & Why!
In a previous blog post about the benefits of flipping your large diaphragm condenser microphones upside down for recording, I discussed some of the earlier tube microphones that generated heat as the day wore on. When I owned Planet V, I used Neumann TLM 149 mics in the booth, which had their own separate power supply for those tubes. These days, your microphone is likely solid state and not using tubes. But it DOES still need 48 volt phantom power. It's a button you'll see on every interface and every preamp. But what is it?
Simply put, it's the power needed to amplify the signal of sound hitting the diaphragm of the mic (that capsule protected by the mesh cage on your mic). 48 volts provides a balance of power and safety: a higher voltage would provide more power to the microphone, but it would also increase the risk of damage to the mic or other equipment. A lower voltage would provide less power and may not be sufficient to operate the microphone properly. It's called 'phantom power' because the power is invisible and it is transmitted through the same cable that carries the audio signal. It's also called invisible because it is transmitted at a very low level and does not affect the audio signal itself. The term "phantom power" was first used by AKG in the 1960s, and it has since become a standard term.
Additionally, 48 volts is typically the voltage at which the input impedance of most audio equipment is highest, which helps to minimize the loss of signal quality over long cable runs. And it's also safe for the most microphone types available on the market, providing enough power for them to work properly while avoiding damage.
For a lot of actors recording at home who perhaps don't use their interface as often as we do at the studio, forgetting to press the 48V power button is a common mistake and reason for not getting signal. If it's happened to you- don't feel bad! You're in great company. I often tell people to just substitute the word POWER for 48V on your interface.