Making the Most Of Your Mixer
MG8/2FX
7
■
The Sturdy XLR
This type of connector is generally referred to as “XLR-type,” and almost always carries
a balanced signal. If the corresponding circuitry is designed properly, however,
XLR-type connectors will also handle unbalanced signals with no problem. Microphone
cables usually have this type of connector, as do the inputs and outputs of most
professional audio gear.
1-2. Balanced, Unbalanced—What’s the Difference?
In a word: “noise.” The whole point of balanced lines is noise rejection, and it’s something they’re very good at. Any length of
wire will act as an antenna to pick up the random electromagnetic radiation we’re constantly surrounded by: radio and TV
signals as well as spurious electromagnetic noise generated by power lines, motors, electric appliances, computer monitors, and
a variety of other sources. The longer the wire, the more noise it is likely to pick up. That’s why balanced lines are the best
choice for long cable runs. If your “studio” is basically confined to your desktop and all connections are no more than a meter or
two in length, then unbalanced lines are fine—unless you’re surrounded by extremely high levels of electromagnetic noise.
Another place balanced lines are almost always used is in microphone cables. The reason for this is that the output signal from
most microphones is very small, so even a tiny amount of noise will be relatively large, and will be amplified to an alarming
degree in the mixer’s high-gain head amplifier.
To summarize:
Microphones:
Use balanced lines.
Short line-level runs:
Unbalanced lines are fine if you’re in a relatively noise-free environment.
Long line-level runs:
The ambient electromagnetic noise level will be the ultimate deciding factor, but balanced is
best.
■
How Do Balanced Lines Reject Noise?
** Skip this section if technical details make you queasy. **
Balanced lines work on the principle of “phase cancellation”: if you add two identical signals out of phase (i.e. one signal is
inverted so its peaks coincide with the troughs in the other signal), the result is … nothing. A flat line. The signals cancel each
other out.
Male
Female
Normal-phase signal.
Reverse-phase signal.
No signal.
(Phase cancellation)
