Apple Final Cut Pro 5 - Manual (Page 815)

28 Part I Media and Project Management
Audio Cables, Connectors, and Signal Levels
When connecting audio devices, you use cables with the appropriate connector on
each end. Audio cables can be either balanced or unbalanced, depending on their
intended use.
About Balanced Audio Signals
For long cable runs, especially when using relatively low microphone levels, a three-
wire balanced audio circuit reduces noise. Balanced audio cables use the principle of
phase cancellation to eliminate noise while maintaining the original audio signal. See
“
Phase ” on page 38 for more information.
Here’s how it works:
A balanced audio cable sends the same audio signal on two wires, but inverts the
phase of one signal by 180 degrees.
When noise is introduced into the cable, it is introduced equally to both the original
and the inverted signal.
Original signal
Inverted signal (reverse phase)
Noise on line
(affects both signals)