29
Unbalancing a Line
In most studio, stage, and sound reinforce-
ment situations, there is a combination of
balanced and unbalanced inputs and outputs
on the various pieces of equipment. This
usually will not be a problem in making
connections.
• When connecting a balanced output to
an unbalanced input, be sure the signal high
(hot) connections are wired to each other, and
that the balanced signal low (cold) goes to the
ground (earth) connection at the unbalanced
input. In most cases, the balanced ground will
also be connected to the ground at the unbal-
anced input. If there are ground-loop problems,
this connection may be left disconnected at the
balanced end.
• When connecting an unbalanced output
to a balanced input, be sure that the signal
high (hot) connections are wired to each
other. The unbalanced ground (earth) connec-
tion should be wired to the low and the ground
connections of the balanced input. If there are
ground-loop problems, try connecting the un-
balanced ground connection only to the input
low connection, and leaving the input ground
connection disconnected.
• In some cases, you will have to make up
special adapters to interconnect your equip-
ment. For example, you may need a balanced
XLR female connected to an unbalanced 1/4"
6. Write the RA number in
BIG PRINT
on
top of the box.
7. Ship the powered mixer to us. We suggest
insurance for all forms of cartage. Ship to
this address:
Mackie Designs
SERVICE DEPARTMENT
16140 Wood-Red Rd. NE, Ste. 5
Woodinville, WA 98072
Balanced Lines
Balanced lines offer increased immunity
to external noise (specifically, hum and buzz).
Because a balanced system is able to minimize
noise, it is the preferred interconnect method,
especially in cases where very long lengths of
cable are being used. A long unbalanced cable
carries with it more opportunity for noise to get
into a system — having balanced inputs means
very little noise will enter the system via snakes
and other cables that typically must run a long
length.
A balanced line is a three-wire system where
two wires carry the signal and the third is a
ground wire that shields the inner conductors
from EMI. The two inner conductors carry the
same signal, but with opposite polarity. The
balanced input amplifies only the difference
between the two conductors. But a signal that
is common to both conductors, and in phase, is
rejected (canceled out) at the balanced input.
This includes hum from AC lines or other EMI
induced noise.
An unbalanced line does not have this
noise-rejecting capability because it has only
two conductors. One conductor carries the sig-
nal and the other is a ground wire that shields
the inner conductor. Any hum or EMI noise
that gets through the shield is added to the sig-
nal and amplified at the unbalanced input.
Often the hum can be louder than the signal itself!
APPENDIX B: Some Arcane Mysteries Illuminated
8. We’ll try to fix the mixer within three
business days. Ask Tech Support for
current turn-around times when you call
for your RA number. We normally send
everything back prepaid using UPS Orange
(three-day air). However, if you rush your
powered mixer to us by next-day air, we’ll
treat it in kind by shipping it back the same
way in which it was received. This para-
graph does not necessarily apply to
non-warranty service.
Summary of Contents for 406M
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