What Is Phantom Power And How Can It Benefit Your Home Recordings?

When venturing into the world of sound & recording, you will inevitably run into the term, phantom power. If you are completely confused by this term and don't have an idea what it means, you are not alone. I was completely mystified myself when I got confronted by it for the first time. But what exactly is this mysterious term?

Don’t worry, you are not about to attempt to summon some supernatural or mythical power from another dimension. I know the term, "phantom power" have this almost otherworldly ring to it. Trust me, it's not that exotic or difficult to understand.

It is very useful though to know exactly what phantom power is, and why it is used in the first place. Let's take a closer look.

Phantom power is the small electrical current that travels through an audio cable to supply power to a condenser microphone or a device (such as a mic activator) that requires an electrical power source to boost the strength of the audio signal.

To better understand this short explanation and really get our head around this "phantom power" term, we need to examine in more detail.

A Detailed Look

In order for phantom power to work, it needs a balanced cable. Which means a cable containing three wires, normally in the form of an XLR cable (You can read more about balanced cables in this article). A direct current (DC) is equally applied through pins two and three of the XLR cable. 

As already mentioned, a fairly low voltage is generated, and the standard for most modern microphones and mic activators are 48 volts. This is more than enough though to meet the requirements of any condenser microphone and other components requiring phantom power to operate.

(A condenser microphone's diaphragm is electrically charged and very sensitive, and requires very little power to operate. The same applies to a mic activator that boosts the weak signal generated by a dynamic microphone. Hence the need for such a small electrical signal.)

A second requirement for phantom power to operate, is a power source. Fortunately, almost all modern audio interfaces, mixers and preamplifiers come with this function build-in. It is normally activated by just pushing a button of flip a switch on the device to send power to the appropriate XLR port. (Normally indicate by "Phantom Power" or "48V" next to the switch.)

But Why Called "Phantom Power"?

Now that you know what phantom power is and why it is used, you may still wonder why it is called phantom power. A very simple explanation actually.

Since the electrical current travels through the audio cable and does not have its own separate power cable, the electrical current is basically "invisible". Hence the term, "phantom power".

A Short History

Phantom power is not a new technology at all. Actually it dates back as far back as 1919, when it was used for the first time to power the "rotary dial" telephone. This same technology is still used today to power "traditional" telephone system. 

Remember, traditional telephone system use a single cable that plugs into the wall socket. Yet there is still an electrical signal that powers the ear and mouthpiece. This electrical signal is provided by the same cable that carries your audio signal. This is one of the earliest examples of the use of phantom power. 

The first commercially available microphone using phantom power goes back as far as 1964 with the introduction of the Schoeps (CMT 20) microphone. It was only in 1966 however, that the condenser microphone powered by the 48V we use today, were introduced with the Neumann model KM 84.

And the first example of the modern condenser microphone using phantom power as we know it today, was born.

Is Phantom Power Harmful Or Dangerous?

Not at all. Especially if you think in term of dangerous or harmful for human beings. One can easy touch the exposed areas of a cable that carries a phantom power signal without any risk of harm. (You probably will not even be aware that you are touching a "live wire".)

Most instruments that do not require phantom power, such as dynamic microphones, will also not be affected at all by the small electrical current. The small voltage will simply be "ignored".

(In very rare cases, ribbon microphones can be damaged by phantom power, but this is normally due to incorrect wiring or "patching", but happens so seldom that its barely worth noting.)  

Similar But Different

Before ending up, there is some confusion and a few heated debates raging about what can and cannot be called phantom power.

I am talking about similar technologies that looks like it its using the same principles as phantom as you came to know it in this article.

I already mentioned the traditional telephone cable. Yes, as I mentioned during the "Short History" section, it does indeed uses phantom power and is one of the earliest examples of the used of phantom power. However, when we talk about phantom power in audio terms today, it exclusively refers to the phantom power in microphone cables. (Specifically XLR cables).

The next technology is probably the most debated and the subject of much controversy when it comes to power. Off course I am talking about the USB Interface. Especially since the introduction of higher quality USB condenser microphone that uses the power supplied by the USB cable, the the topic heated up significantly.

• There are a those that argue that the USB condenser microphone powered by the USB cable, is no different than the traditional condenser microphone powered by the phantom powered supplied by an audio interface or mixer to its XLR cable. 
• Then there are your audiophiles and purists that vehemently oppose this assumption. For them the quality and power supplied to USB condenser microphones does not come close to "real" phantom powered condenser microphones in an traditional professional audio setup.

Lets address the term, "phantom power" first. Because the power in the audio cables are "invisible" to the user, and no extra power cable is required, the term "phantom power" was coined to refer this technology.

When you look at it in these simple terms, you can see the point of those arguing that USB powered microphones use "phantom power". After all, one cable is used to carry the data signal as well as supplying the microphone with electrical power. Isn't this the very definition of "phantom power". In a way, yes.

Things become more difficult when you look at the different technologies employed by "traditional phantom"  and the USB Interface respectively.

Without getting into boring detail, I can just tell you what many of you already know. First of all the interfaces are very different. Obviously all the different connections will not fit each other. You cannot plug an XLR audio cable into an USB port and vice versa.  (And no, simply using an adapter will not solve the problem.)

Secondly, the traditional phantom power supplied by audio interfaces is 48V, while the vast majority USB Interfaces only produce 5V of power through its cable. (Needless to say, the 5V power supplied by the USB Interface will not be nearly enough to activate and power a traditional condenser microphone.)

The way in which the power is delivered also differs quite significantly. The DC power in a XLR cable uses the same amount of voltage through pins two and three to power the condenser microphone. This is very different from the way an USB Interface provides power to its microphone. I am not going to bore you with the details, but it simply means that even if the voltage of the two technologies were the same, the way in which power is delivered makes them incompatible.

So where does this leave us?  Well if you look at the principle of why "phantom power" is called "phantom power", you can understand why so many users see USB condenser microphones as no different than traditional condenser microphones using 48V phantom power.

But as I pointed out, both the strength of power, as well as the way in which this power is supplied, differs significantly between USB and traditional 48V phantom power. From this point of view, "phantom power" provided by the USB interface is not at all the same as traditional 48V phantom power produced by audio devices.

(You can now see why I spend so much time on this issue, as it can be confusing, and you will no doubt be confronted by it as some point. I feel its important that you rather have a better understanding of this contentious issue now, so that you are not confused or caught off-guard whenever the topic comes up.)

I will just end by saying that so far, the general consensus among audio users, is that the term "phantom power",   is reserved for conventional 48V audio cables used in recording studios.

(I am not commenting on the quality of USB condenser microphones or disputing the argument that some of them produce quality on par with many studio microphones. That is not the issue at stake here though.)  

Conclusion

As you can see, phantom power is not as mysterious as the name suggests. At the end of the day it is simply the low voltage power that "hides" in your microphone's audio cable.

(The technical ins-and-outs may be a bit more complicated, but not necessary for us to understand what it is and how it works.)

As always, feel free to leave me any comments or suggestions you may have, and I will respond and try and get to them as soon as I can.

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Catch you in the next article and happy recording!

Wessel