more than a microphonewe talk about the phantom or phantom power, which has been with us for many years and is very popular in these products. Let’s go a step further with the microphone feed and explain it to you in detail.
Phantom or phantom power has a history behind it and dates back to 1965 thanks to the Neumann brand. It is still used today, showing that its virtues are enough to bet on this power supply in microphones. We explain everything about it.
What is phantom power on a microphone?
It is a way to supply power to microphones through different sources, such as mixers or mixers, microphone preamps, audio interfaces or phantom power supplies.
Power travels from source to microphone through the same cable that the audio signal is sent of the mic. In this way, there is no dedicated cable to supply power to the microphone, but the phantom microphone receives audio and power through the same cable. It is for this reason that it is called “ghost”.
This feed is used to power the components of the microphones assets: impedance converters and preamplifiers that they have inside. That said, we recommend you read about the condenser microphone because the phantom is used for its capsules: it needs an external polarization.
A normal phantom power is usually +48 volts DCwhich is what we will get in professional sources, but it usually varies between 12 and 48 volts (such as between 4 and 22 milliamps). Say that these cables that the phantom power and audio travel through are balanced.
Hence the immediate appearance of the cable XLR, applying the voltage at the same level between pin 2-1 and pin 3-1, there being no voltage between pins 2-3. We already explained that an XLR cable has 3 balanced pins:
- Pin 1: ground connection.
- Pin 2: positive audio signal.
- Pin 3: negative audio signal.
The audio is sent through pins 2 and 3, the first carrying a positive polarity signal and the second another negative polarity in the same signal. Therefore, a balanced input requires an amplifier that adds the difference between pins 2 and 3. So, it can be said that the final audio signal is the sum of 2 audio signals.
By this we mean that the microphone that uses phantom power you will not have more noise in the signal by this method of power supply. In the world of audio, noise or electromagnetic interference are the biggest enemies, so it is interesting to emphasize this.
Brief history of phantom microphones
We have to go back to the 1960swhen used transistors in condenser microphones, at which point there was a need to feed power to the microphone through a cable.
we came to see vacuum tube microphones since the beginning of twentieth century, until Bell Labs invented the transistor in 1947: they were smaller than vacuum tubes and needed less power. we would have to wait until 1966 for what Neumann introduce the KM 84the first phantom powered microphone. Note that Schoeps produced the first solid-state microphone with transistors in 1965, but he was not the first to use phantom power.
But who invented phantom power? We know that the transistor, Bell labs, and that the first microphone with such power was Neumann. However, it would be NBC or NRK (Norwegian Broadcasting Corporation) which invented this type of feed.
It all comes about because daylight in the Norwegian months is very limited, so they needed to provide auxiliary light through a +48 volt DC source. So Neumann visited NRK to sell his solid-state microphones, but what about the power supply?
It was decided to take advantage of the +48 volt DC supply from NRK studios for the microphones, so Neumann would design it this way: the voltage runs on pins 2-3 of the XLR cable.
phantom power supplies
The time has come to know where all that food that is being talked about originates from. Logically, everything arises in the electrical network or in the batteries, but the power sources are:
- The mixers or mixers.
- Audio interfaces.
- Microphone preamps.
- Dedicated phantom power supplies (convert plug or battery electricity into phantom power for microphones).
Is there phantom power through TRS?
We have already seen that there are other types of connectors or cables that “rival” the XLR, and those are the TRS. We know that XLRs are widely used for phantom power, but the truth is that TRS cables are supported with phantom power on microphones.
How? In a TRS cable we have a tip, ring and sleeve, but the phantom power is sent at +48 volts at the tip and ring (positive-negative). It is normal to see this feed on XLR cables, but it can also be sent via TRS.
In which microphones is phantom power used?
With all the above, you will conclude that we see this power supply in a condenser microphone that uses XLR or TRS, right? You are not misguided, but the truth is that you have to refer to microphone design and your energy needs.
There are passive microphones whose DC voltage is stopped at the body of the microphone, blocking the power it doesn’t need. On the other hand, passive ribbon microphones block that excess voltage across passive ribbon microphones.
The risks of phantom power on a microphone
There are 3 clear situations in which a microphone can be damaged through phantom power:
- Short circuitproduced when voltage is sent to one conductor instead of both.
- Power surge, something that is out of our control on many occasions. It is recommended to protect professional studios with power conditioners to prevent any microphone or audio equipment from being damaged through a power surge.
- unbalanced microphones, in the case of forcing phantom power via an unbalanced cable. In this scenario, you would overload the microphone after putting 48 volts into a cable that is not balanced (karaoke, lavalier mics, etc.).
What about if He microphone does not need phantom power? Put the focus on 3 microphones:
- The ribbon microphonesdue to the fragility of the ribbon diaphragm.
- lavalier microphones and karaoke, for being unbalanced.
These mics would be damaged if phantom power was used on them, but the good news is that they don’t usually use XLR connectorsso it will be difficult to use phantom power (unless they are TRS).
digital phantom power
Although we have already talked about XLR as the ideal cable for balanced or balanced microphones, in digital phantom power the cable XLD, which is a variant with a different slot. That different slot helps you avoid switching between digital and analog devices.
What makes it different from normal phantom power? It is delivered in much the same way, but the analog P48 (+48V) supplies do not supply digital P10 (+10V DC), sending power via XLR or XLD. Basically, the Audio Engineering Society published the standards AES 42 con 10V CC phantom power for digital microphones.
This means that the digital microphones that comply with AES 42 require phantom power of 10Vand the current can be up to 250 milliamps.
Ok, but what is a digital microphone? Currently, we find digital and analog microphones. Analog microphones convert sound waves into electrical audio signals, but digital microphones have analog-to-digital converters, outputting digital audio.
So the difference is in the output:
- Analog outputs analog signals (using XLR or TRS).
- Digitals output digital signals (USB).
Alternatives to the microphone with phantom power
There is another method to supply power to a microphone other than phantom power, and we find the following:
- DC-biasing (1.5-9V), famous for lavalier microphones and for electret microphones.
- Power T (AB), was one of the first methods to power a condenser microphone, but has succumbed to the phantom.
- Plug-in Power (PiP), it is used for domestic electret microphones (laptops, gaming headsets, etc.), it supplies +4V in DC and balanced cables are not used.
- Batteriesin the case of those microphones that come with batteries.
- External power suppliesfor microphones that require more power than the phantom (+48V), such as tube microphones.
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