From the May 2017 issue of Acoustic Guitar | By DOUG YOUNG

I f you've used microphones for alive performances or in the studio, yous've almost certainly encountered phantom power—that slightly mysterious-sounding button found on many mixers and preamps. Phantom ability provides a source of electricity to some microphones. Near of the time, the phantom-ability feature but does its job silently, but a bit of knowledge can help when things get wrong or when choosing the gear with which you lot piece of work. Equally a guitarist, you may also come across some less common scenarios related to phantom power.

These pointers volition help demystify phantom ability.

Now Y'all See It, Now Y'all Don't

Phantom power is a way to provide power to microphones that crave electricity to operate, typically condensers. On the other hand, dynamic mics—the ubiquitous Shure SM57 and SM58, for example—practice non require power. Phantom power involves a clever scheme that leverages the multiple wires in a typical balanced-XLR cable to provide voltage to mics that need it without affecting those that practice not, in most cases. You lot can ordinarily plug either type of mic into a mixer that provides phantom power, and the condenser mic will detect and utilize the power, while nearly dynamic mic will ignore it. This trick is why the scheme is referred to as phantom—information technology's there for mics that demand information technology, simply generally invisible to others!

One complexity with phantom ability is that there are multiple standards for voltage levels. Most modern mixers provide 48 volts, which has become so common that many people presume that phantom power automatically means 48 volts. Notwithstanding, the ANSI standard (IEC 61938) that covers such things allows for 12, 24, and 48 volts. As a result, you may encounter gear that supports any of these voltages. Several popular audio-visual guitar amps provide 24 volts. One popular acoustic preamp fifty-fifty provides just 15 volts.

In most cases, these different levels should not cause concern. Most mics work fine over the voltage range of 12-48 volts, although many mic manufacturers specify 48 volts for all-time operation, and some mics may be more than problematic than others when encountering lower levels of phantom ability—yous may notice some loss of output or sensitivity with lower voltages. In any instance, a lower voltage won't damage the mic, so you can ever come across for yourself if a lower voltage will piece of work.

Phantom power is a complex subject, merely for most of us, it's a matter of matching the requirements of our mics—or other gear—with the features of the mixer.

Some DIs or preamps tin be powered by phantom power (the popular L.R. Baggs ParaDI, for example), and these may non piece of work with lower voltages. The amount of current provided by the phantom power source is some other factor. Most mics crave only a few milliamps of electric current, which whatsoever mod mixer should hands support, but some mics—also every bit phantom powered preamps—may have college current demands. Some studio microphones, most notably tube mics, crave so much power that they use their own dedicated power supply instead of relying on phantom ability.

Although it is usually safe to plug a dynamic mic into an input that provides phantom power, there are exceptions. Some ribbon mics (usually used only in studios) can exist damaged by phantom power if a cable or the mic is mis-wired. Information technology's a good idea to be wary of whatsoever vintage microphone or one that has been modified in any nonstandard mode. It's too best to plug microphones in before turning on phantom ability. At the very least, doing so while phantom power is active can cause a loud, audible pop from the speakers if the volume is upwards. In addition, plugging in other electronic devices—a keyboard or an effects pedal that has an XLR out, for example—is less certain. Check your instruction manual to exist sure that the device is safe for phantom power, and assume that information technology is not safe if the manual is silent well-nigh the issue. For multiple reasons, it'due south a good practise to use a DI between such devices and a mixer, including isolating them from phantom power.

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Other Powering Schemes

A frequent source of confusion for guitarists is that some microphones use different powering schemes. One such approach is known as bias power—also chosen plug-in-power. Bias power is ofttimes required past internal guitar mics, as well as mics used with some portable recorders, wireless systems, and more than. Bias power uses a two-wire organization, different the XLR three-wire system supported by almost mixers. A voltage, usually around 5-9 volts, is applied directly to the mic's "hot" wire. This voltage is not "phantom," and you cannot use bias-powered mics directly with a phantom power supply, or vice versa.

Acoustic guitarists oft encounter bias-powered mics as part of dual-source pickup systems. In commercial dual-source systems with onboard electronics, such equally the L.R. Baggs Anthem or DTar Multi-Source, the mic is powered by the onboard electronics and bombardment, so yous don't fifty-fifty have to be aware of it. Simply many guitarists similar to build their own systems past adding a mic, such as Grand&Chiliad Sound's Silver Bullet mic, to an existing pickup. In these cases, the mic tin can exist powered by wiring it to the ring terminal of a stereo jack in the guitar, and then using a stereo guitar cablevision to plug into an acoustic guitar preamp that provides the bias ability on the ring of the cable. The Grace Felix and Headway EDB-2 preamps are examples of guitar preamps that support this feature. Rolling your ain dual source pickup organization can be daunting, and requires planning out your entire system. A good guitar tech tin clear up any confusion and help you ready such a system correctly.

Unfortunately, many preamp and guitar-amp manufacturers incorrectly label bias ability equally "phantom" power—they are not the aforementioned thing! Notwithstanding, the divergence is commonly obvious from the connectors: If you have an amp or preamp that provides power for a mic, an XLR-mic connector almost certainly indicates existent phantom ability. A system that provides ability through a stereo ¼-inch guitar jack generally indicates bias power. The mics are like—a mic with an XLR connector expects phantom power, a mic with ii wires, or a simple non-XLR connector, probably expects bias power.

Phantom power is a complex subject field, but for most of us, it'south a affair of matching the requirements of our mics—or other gear—with the features of the mixer. When in dubiety, consult your educational activity manual or get in affect with the manufacturer.