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If you’re a budding musician, podcaster, or audio enthusiast, you’ve probably come across the term “phantom power” when dealing with microphones. Phantom power is a mysterious-sounding term, but it’s a crucial aspect of audio recording that can greatly affect the quality of your sound.
In this article, we’ll explain why you need it for certain microphones, discuss its impact on sound quality, and provide some practical tips on its usage.
Phantom power is a method of supplying electrical power to the active circuitry in certain types of microphones, typically condenser microphones.
Condenser microphones, also named capacitor microphones, are known for their active circuitry inside their mics, their sensitivity, and their ability to capture fine sound waves, making them a popular choice for studio recordings, podcasts, and live performances.
These microphones function based on an electrical principle known as variable capacitance. Within the capsule of a condenser mic lies a thin membrane typically crafted from mylar, referred to as the diaphragm, alongside a metal backplate.
When sound waves, whether from a voice or a musical instrument, impact the diaphragm, its exceptional sensitivity enables it to oscillate back and forth. This oscillation alters the separation between the diaphragm and the backplate, consequently modifying the capacitance or the stored electrical charge.
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. What differentiates condenser mics from other mics is their need for an external supply.
During the 1930s to the 1950s, condenser mics relied on bulky external power supplies. In the 1960s, Neumann and Schoeps embarked on a mission to develop a revolutionary energy solution that would eliminate the need for an external power supply to power active microphones. An exception to this is tube microphones, which are a type of condenser that still use external power supplies.
This innovative approach established +48V as the new industry standard for powering condenser mics, sending phantom power from the mixer through the XLR cable to the microphone input of balanced microphones.
This groundbreaking and virtually invisible energy supply was called “phantom power.” This in turn led to the release in 1964 of the Schoeps Model CMT20, the first commercially available phantom-powered microphone.
Energy for mics can come from either an internal battery or more commonly these days, direct current (DC) power is supplied by the preamp or mixer and transmitted to the condenser mic via a balanced mic cable.
For it to operate, it necessitates the use of a balanced microphone cable. A balanced mic cable comprises three conductors: Pin 1 functions as the ground, Pin 2 carries the audio’s positive signal, and Pin 3 handles the audio’s negative signal. In most microphones, the application of sound pressure to the diaphragm generates a positive voltage on Pin 2.
Phantom power typically ranges from 9 to 52 volts DC and is simultaneously applied across both Pin 1 and Pin 2, as well as Pin 1 and Pin 3. The term derives its name from the fact that when measuring across the two audio lines, namely Pin 2 and Pin 3, you will find a voltage reading of 0 Volts DC.
Furthermore, despite this voltage coexisting on the same pins as the audio signal, it does not interfere with the mic’s signal integrity.
The international standard for mics that need phantom-powered input typically ranges from 11 to 52 volts of DC, with typical studio microphones running on 48 volts. Your preamp usually includes a 48-volt switch, allowing you to activate or deactivate phantom power as needed.
Unlike dynamic mics, which generate their own electrical signal through electromagnetic induction to transmit audio signal, condenser microphones require phantom power to operate. This energy source is provided through it, usually delivered via the same mic cable used to transmit audio signals.
Phantom power is unnecessary for a dynamic microphone because it lacks active electronics within its design. They contain a mechanical moving coil that vibrates from acoustic energy and sends an electrical signal for recording.
Dynamic microphones are more robust than condensers, i.e., less sensitive, and can tolerate higher SPLs without distorting. They are passive and do not require +48V power.
Modern dynamic microphones are designed to accept phantom power without issues, even when they don’t need phantom power, but check your manual or consult with the manufacturer first before connecting; particularly if you have a ribbon microphone.
You should never send phantom power to ribbon mics. Apart from modern active ribbon mics which require phantom power, it can damage the sensitive internal components of older passive ribbon microphones.
Some ribbon mics can be damaged by it if a cable or the mic is miswired. It’s a good idea to be wary of any other microphones or one that has been modified in any nonstandard way. When not in use, it is best to disable the phantom power supply to avoid any potential damage to your mics.
Phantom power supplies are often built into mixing consoles, microphone preamplifiers, and similar equipment. In contrast, it is seldom available from instrument amplifiers. When using equipment that needs phantom power with these amplifiers, you’ll need to insert a separate power supply into the signal chain.
However, it’s worth noting that some older mixers and budget-friendly analog interfaces may also lack phantom power capabilities. In such cases, an external phantom power supply can be inserted between the condenser microphone and the preamp to provide the necessary energy.
Occasionally, people mistakenly use the term “phantom power” when they are actually referring to one of the following energy sources. It’s important not to confuse these different energy options, as they serve distinct purposes.
Phantom power is not the sole method of providing voltage to mics. Some condenser microphone models utilize batteries to supply energy to their internal circuitry. It’s advisable to remove batteries when the microphone is not in use to prevent corrosion and potential damage to its internal components.
Plug-in power (PiP) is a low-current energy supply commonly found in consumer-grade equipment such as portable recorders and computer sound cards. This interface operates at a lower voltage and is unbalanced, making it fundamentally different from phantom power. It’s crucial never to use 48V with a microphone designed for PiP.
The term “phantom power” is sometimes inaccurately used to describe the small electric current that powers aviation microphones. While technically it is “phantom” in the sense that it cannot be seen, DC voltage operates at a significantly lower current of electric power, typically ranging from 1.5 to 9 volts. In the realm of audio engineering, this type of voltage is generally used to power microphones like miniature lavaliere (lav) microphones.
Phantom power itself does not directly improve the sound quality of a microphone. Instead, it ensures that the microphone operates at its optimal performance level. When a condenser microphone has the necessary energy, it can capture audio with greater detail, accuracy, and sensitivity, resulting in better sound quality.
Most modern mixing consoles provide phantom power, as do external audio interfaces, certain audio recorders, and video cameras. However, not all of these devices are guaranteed to be external phantom power supplies for your mics.
That being said, the ultimate sound quality also depends on the microphone’s design, build quality, and the acoustic environment in which it is used. While phantom power is essential for condenser mics, other factors play a role in achieving the best sound possible.
Since phantom power is only routed through the mic signal, the DC current isn’t going to affect anything else connected to your interface or console. Wireless mic receivers are balanced and can handle the DC voltage safely.
However, when you connect or disconnect a balanced XLR cable while leaving the phantom power on, it can result in clicks or pops, which could in time damage your speakers or headphones. So it’s generally a good idea to disable it when plugging or unplugging your mics.
Phantom powering may still cause equipment malfunction or even damage if used with cables or adapters that connect one side of the input to the ground, or if certain equipment other than mics is connected to it.
Leaving it on when it’s not needed won’t typically harm your microphone. Modern condenser mics are designed to handle phantom power without any issues. However, there are some considerations to keep in mind:
To avoid unnecessary energy consumption, it’s a good practice to turn phantom power off when you’re not using condenser mics. If an unbalanced and sensitive microphone – like a ribbon mic, or old dynamic mic – is connected, it may get damaged. So never connect unbalanced microphones or cables to phantom-powered inputs.
Using phantom power for your microphone is straightforward:
Remember to turn off phantom power when you’re finished using your condenser mic to save energy and prevent unnecessary wear on your equipment.
Phantom power is a vital component of the audio recording process, especially for condenser microphones. It ensures that these sensitive mics receive the electrical power they need to capture audio accurately. While phantom power itself doesn’t inherently improve sound quality, it enables your microphone to perform at its best.
Just remember to use it responsibly, turning it off when not in use, to conserve energy and prolong the life of your equipment. With this knowledge, you can confidently harness the power of phantom power to achieve professional-quality audio recordings.