Balanced Cables (page 2)
Microphone Level and Line Level
Audio and video recorders (and playback devices) usually have two types of inputs (outputs): microphone level and line level. Microphone inputs are for microphones and line inputs are for other equipment, such as CD players and tape decks. The difference between microphone and line inputs is the amount of power of the signal. CD players and similar equipment usually have some means of amplifying the audio signal. Microphones do not, so they need the extra amplification provided by the recorder. Therefore, you should always make sure the microphone is plugged into a microphone input and not into the line input. Actually, this is a rather easy problem to diagnose: if you plug a microphone into a line input, the signal will be way too soft. Connecting a line source to a microphone input can be even easier to diagnose: you'll know it immediately by the loud and painful sounds screaming through your headphones. Be more careful about plugging in line sources. A microphone into a line jack will yield poor audio, but a line source into a microphone jack has the potential to damage your equipment.
Who Should Use Balanced and Why?
Unbalanced cables and high impedance accessories are fine when you can get away with it, for example with very short cable runs. Also, an inexpensive microphone and unbalanced cable is almost always better than just using the on-camera microphone. In a professional situation (i.e. one where you're being paid), you want to isolate the sound source, and eliminate any potential for hum. Balanced cables eliminate hum. Using an external microphone of low impedance is best in an interview situation or when it is not possible to get close to your subject.
Go Pro
Actually, much of this discussion is not up for discussion: we can't think of any decent microphones that come with anything other than XLR connections and, by extension, work with balanced cables. So you'll almost certainly be using balanced connections, whether you care to or not. You'll just have to be flexible about the whole situation and adapt.
Garret Maynard is a film-video maker and guest lecturer, and lives in Connecticut & Vermont.
[Sidebar: Testing Cables]
It makes sense to test your audio connections and recording quality before you videotape an important event. The best way to do that is to connect everything and do a test recording. Make sure that your test conditions are similar to the event conditions. In playback, if you get low audio or a buzz through the headphones, it's time to troubleshoot. If you are using an external microphone, check to see if the impedance matches, check for parallel cables and ill fitted adapters. It also could be a broken cable. If you are connecting to a mixer, check it for signal continuity. It's a good idea to get to the location early to allow enough time for problem solving. Finally, if you have a buzz you just can't get rid of, try using only battery power with your camcorder: sometimes the source of your hum is the AC power to your camera.
