We should all live a balanced life, right? At least that’s what we’re told. Eat less salt, consume more fish oil, and don’t forget a healthy dose of exercise. We balance work and family, fun and career. Why not balance your audio connections too? It’s not that hard to do and the benefits far outweigh any additional bother or cost. Before you buy a year’s supply of multi-vitamins and an Ab-Master, take a look at these tips for using balanced audio cables and connections to improve the sound in your videos.
How Does It Work?
Way back in the early days of electricity and telephone connections, electrical engineers needed to solve a very specific problem. Delicate signals faded too quickly or became unusable over long distances. They came up with a clever solution to this problem: balanced cables. By balancing their wiring, they achieved two very important improvements. First, they were able to control the noise that crept into the signal. Second, they could run the cables for hundreds, even thousands of feet before seriously degrading the signal. Of course, today, we use fiber optics, microwaves and satellites to transmit our phone conversations, but the balanced connection is the foundation of professional audio.
We’re sure you’ve picked up interference on your cell or cordless phone, but imagine how much interference a radio or television engineer deals with sitting under a tower spewing 100,000 watts of energy. It’s absolutely critical that they use balanced audio connections to eliminate the sea of noise trying to muscle into their signal path. And since professional audio is an offshoot of the broadcast industry, it was logical for them to use the same cable technology.
Balancing an audio connection requires three separate wires. One wire carries the signal; this is the part you want to keep. A second wire carries a copy of the signal, but it is inverted 180 degrees out of phase with the original signal. The third wire is the ground connection and serves as a zero-signal reference for the other two wires.
There’s one more component in a balanced microphone cable – the shield. This is often an aluminum foil wrap surrounding the entire length of the microphone cable. Alternatively, you’ll find some cables use a copper braid or individual strands wrapped around the inside wires. Just as the name implies, this shield serves as a first line of defense to minimize the amount of interference that makes it’s way into your cables.
Ins and Outs
Along with the cabling in a balanced signal, there are also several standard balanced connectors. The most common balanced connection is the XLR plug. Found on everything from microphones to mixers, the XLR cable gets its name from the series number assigned to it by an early manufacturer. Now the term is used generically much like Band-Aid, Velcro and Kleenex. From time to time, you’ll hear people refer to XLR connections as "cannon" or 3-pin plugs, but they all mean the same thing. One standard place you’ll find an XLR is on the bottom of many handheld microphones. This is a standard connector in professional audio circles because of the durability and reliable connection. Available in male and female versions from various manufacturers, all XLR connections work interchangeably and serve as an excellent balanced audio connection.
Another common balanced connector is the 1/4-inch plug. Often called a phone or TRS plug, these connectors are most often used on audio mixers and other signal processing equipment. TRS stands for Tip Ring Sleeve and refers to the three connecting points on the plug. The 1/4-inch phone plug is a leftover from the old days of operator-assisted telephone calls. The operator would answer your call, and then physically plug your call into a jack on a large panel, electrically connecting you to the person you wanted to call. Of course, all of the switching is all handled by computers today, but the 1/4-inch phone plug remains a common balanced audio connector. We’re sure you recognize this plug when you see it, but not all plugs of this size and shape are balance.
Virtually all other audio connections are unbalanced. The RCA plug and 1/8-inch mini plug are both unbalanced and there are unbalanced versions of the 1/4-inch phone plug (stereo and mono), but they only have the tip and sleeve connections. If all of this seems confusing, just remember: it takes three wires for a balanced audio connection.
Now that you have your balanced microphone and cable, where do you plug it into the camera? Because balanced audio is considered a professional feature, camcorder manufacturers often only include these connections only on their upper-tier products. You’ll have to spend a few thousand dollars to find a camera that has built-in balanced audio support. Most cameras under $3,000 only offer 1/8-inch stereo inputs for external microphones. If you have a couple hundred dollars for a professional microphone, but you don’t have a few thousand for the professional camera, don’t worry: there are a couple of excellent ways around this limitation.
The first is a trip to your local electronics retailer or music store. First, run your long XLR cable from your microphone all the way to your camcorder. Then, fit an XLR to 1/4-inch adapter (mono) on the end – these are common at music stores, but many national electronics stores have them too. Then connect a 1/4-inch to 1/8-inch adapter to that. At this point, you could plug straight into your camcorder with the 1/8-inch male plug, but we’ll connect another short adapter cable right at the camcorder end to eliminate any potential damage to your camera from heavy connectors hanging off the side.
If you’re not the do-it-yourself type, there are a couple of manufacturers (such as BeachTek) that make one-box solutions for connecting balanced microphones to the 1/8-inch microphone jack on your cam-corder. These boxes either mount to the bottom of your camcorder or clip on your belt and usually have gain controls and other options to get you connected to almost any balanced audio source.
Using balanced audio is a bit more trouble and includes some added expense, but the benefits are instantaneous and easily recognizable. You’ll gain the ability to run long mike cables and the only noise in your recorded audio will be the birds singing in the trees. This gives you more flexibility during the shoot and less hassle during your edit session. Aside from better hours and more pay, what else could you want?
Sidebar: Balanced Audio – A Visual Description
Balanced audio can be difficult to understand. So here’s a graphical representation of how noise gets cancelled in a balanced cable. Start your favorite photo-editing program and open a picture with some detail. Change it to grayscale, then duplicate the image on another layer. Invert the colors of the copy – now you have a negative of the original image. Adjust the opacity of the inverted layer to 50%. The images completely cancel each other and you’ll be left with a solid gray picture. That’s exactly what happens to unwanted interference and noise when they attempt to invade a balanced audio connection.
Sidebar: Mix And Match
In the world of video, it’s common to combine a variety of balanced and unbalanced audio signals. The most flexible way to do this is with a full-featured audio mixer from a manufacturer like Behringer, Mackie or Yamaha. Many models are perfectly suited for the video producer who needs to use one device in multiple applications, so you can maximize your investment. Besides, the audio mixer you buy today will probably be the same one you are using ten years from now. Along the way, you’ll also collect a wide variety of audio adapters and cables to interface the never-ending list of microphones, receivers, audio mixers and playback devices. There’s only one rule: You can never have too many adapters.