Apple Final Cut Pro 7 - Manual (Page 212)

Now, both audio signals are in phase, but the noise is inverted, causing the noise to be
canceled. At the same time, the original signal gets a little stronger because it is sent on
two wires and combined. This helps compensate for the reduction in signal strength that
occurs naturally on a long cable run.
Combined signals
(noise eliminated)
Any noise introduced into the cable across its long run is almost completely eliminated
by this process.
Note: Unbalanced cables have no way of eliminating noise and are therefore not as robust
for long-distance cable runs, microphone signals, and other professional uses.
Connecting Professional Audio Devices
The steps for connecting audio playback and recording devices are similar to the steps
for connecting professional video devices. Many professional audio-only devices such as
DAT recorders and Tascam DA-88/DA-98 multitracks support remote device control and
audio insert editing.
If you plan to capture footage using separate video and audio interfaces, you may need
to set up additional synchronization between your audio device and audio interface. For
more information, see
“Synchronizing Equipment with a Blackburst Generator.”
Connecting Professional Digital Audio Devices
Professional digital audio devices often use balanced XLR connectors. Each XLR connector
carries two AES/EBU digital audio channels. Connect the digital audio outputs of your
video or audio device to your audio interface (or its breakout box). If your video interface
has the appropriate connectors, you can also connect the audio outputs of your device
to the audio inputs on the video interface.
Note: Professional analog audio devices also use XLR connectors, but the signal is
incompatible with AES/EBU digital audio.
Connecting Consumer Digital Audio Devices
Consumer devices such as CD players, MiniDisc recorders, and some DAT recorders use
either an optical or RCA (coaxial) connector for S/PDIF digital audio. S/PDIF carries two
channels of digital audio, usually at a sample rate of 44.1 or 48 kHz and a bit depth of
16 bits. Connect the S/PDIF output of your audio device to the S/PDIF input on your audio
or video interface, if available.
212 Chapter 12 Connecting Professional Video and Audio Equipment