Yamaha EMX512SC Owner's Manual | Page 14

Yamaha Musical Instruments Owner's Manual - EMX512SC.
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14

EMX512SC/EMX312SC/EMX212S

Making the Most of Your Mixer

BASIC

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.

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.

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.

A balanced cable has 
three conductors:

1) A ground conductor which 

carries no signal, just the 
“ground” or “0” reference 
against which the signal in the 
other conductors fluctuates.

2) A “hot” or “+” conductor which 

carries the normal-phase audio 
signal.

3) A “cold” or “–” conductor which 

carries the reverse-phase 
audio signal.

While the desired audio signals in 
the hot and cold conductors are 
out of phase, any noise induced 
in the line will be exactly the same 
in both conductors, and thus in 
phase. The trick is that the phase 
of one signal is reversed at the 
receiving end of the line so that 
the desired audio signals become 
in-phase, and the induced noise 
suddenly finds itself out of phase. 
The out-of-phase noise signal is 
effectively canceled while the 
audio signal is left intact. Clever, 
eh?

Hot

Cold

Shield 

(Ground)

Outer

 Insulation

Balanced

Unbalanced

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.

Balanced noise cancellation

Noise

Hot (+)

Cold (–)

Ground

Source

Cable

Noise cancelled

Noise-free signal

Phase 
inversion

Receiving device

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