What is Phantom Power and why do I need it?
Overview
In this article, we will discuss what phantom power is, why you need it, and answer some commonly asked questions. Follow the sections below to get started.
What is phantom power?
To know what phantom power is, you need to understand how condenser microphones work. Condensers work on the principle of variable capacitance. In Britain, they are actually called “capacitor microphones.” Sound waves vibrate a diaphragm (usually gold-sputtered mylar) that is stretched in front of a metal plate (called the backplate). As the diaphragm vibrates, the distance between the diaphragm and the backplate changes, which changes the capacitance.
Those tiny electrical variations which must be amplified before they leave the mic so there’s an internal preamp inside the mic. The phantom power provides the voltage to charge the diaphragm and also powers the preamp inside the mic.
This amplification method is what’s known as phantom power.
Why do I need phantom power?
Phantom power, commonly designated as +48V or P48, was designed to power microphones without using bulky external power supplies such as the ones required for tube microphones. It’s a way of sending the DC electrical current required through a balanced XLR cable. We need that voltage to power the diaphragm and the mic’s internal amp. When phantom power is turned on, DC current is sent through the XLR cable and delivers the voltage necessary to power the microphone. It’s most widely used as a power source for condenser microphones, which have active electronics. In addition, true condenser microphones (as opposed to electret) require a voltage for polarizing the microphone’s transducer element, and phantom power provides a voltage for both of these purposes.
“Signal flow” of phantom power
Phantom power FAQ
Now that you know how phantom power is and why it’s required, here are some of the most commonly asked questions we receive about phantom power. We’ve also included some tips and tricks to help get the most out of your phantom powered gear.
Do I need phantom power for my guitar?
Phantom power is not required for your guitar. However, some active guitar DI boxes will need it. Refer to the DI box Owners Manual for specific power requirements, however.
Why isn’t my condenser microphone working even with phantom power turned on?
Besides a potentially bad cable, one reason could be that it isn’t receiving enough power. Some older or inexpensive consoles or interfaces may have Phantom Power buttons, but they supply a lower voltage, less than 48 volts.
While some condenser microphones can operate on voltages as low as 9 volts, providing less than 48 volts may cause sonic degradation and decreased performance. In cases like these, you will need an external power supply.
Can you damage a ribbon microphone with phantom power?
This is a hotly debated topic, and the answer is “not necessarily.” Active ribbon microphones will require phantom power. However, ribbon microphones should never be plugged into a preamp with phantom power engaged. There are two ways you can damage a passive ribbon microphone. Improper wiring of the XLR cable used, and live patching (also known as hot-patching) on a TRS patch bay. Check out this article to learn about the relationship between ribbon mics and phantom power from our friends at Royer Labs.
Do I need phantom power for a dynamic microphone?
Dynamic microphones do not require phantom power. However, there are some very low-output dynamic microphones, such as the Shure SM7B (with an output level of -69dBV). These microphones require a preamp to boost the signal. If you are using an in-line preamp that requires phantom power, then after you connect the microphone to the preamp, you will then need to enable phantom power to run the preamp.
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