43
goes to the ground (earth) connection at
the unbalanced input. In most cases, the
balanced ground (earth) will also be
connected to the ground (earth) at the
unbalanced 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)
connection should be wired to the low
(cold) and the ground (earth) connections
of the balanced input. If there are ground-
loop problems, try connecting the
unbalanced ground (earth) connection
only to the input low (cold) connection,
and leaving the input ground (earth)
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
"
TS phone plug.
SPECIAL MACKIE CONNECTIONS
The balanced-to-unbalanced connection has
been anticipated in the wiring of Mackie jacks.
A
1
⁄
4
" TS plug inserted into a
1
⁄
4
" TRS balanced
SWITCHED
1
⁄
4
" PHONE JACKS
Switches can be incorporated into
1
⁄
4
"
phone jacks, which are activated by inserting
the plug. These switches may open an insert
loop in a circuit, change the input routing of
the signal or serve other functions. Mackie
uses switches in the channel insert and bus in-
sert jacks, input jacks and AUX returns. We
also use these switches to ground the line-level
inputs when nothing is plugged into them.
In most cases, the plug must be inserted
fully to activate the switch. Mackie takes
advantage of this in some circuits, specifying
circumstances where you are to insert the plug
only partially. See
Special Mackie
Connections
, later in this section.
RCA PLUGS AND JACKS
RCA-type plugs (also known as phono
plugs) and jacks are often used in home stereo
and video equipment and in many other appli-
cations (Figure D). They are unbalanced and
electrically identical to a
1
⁄
4
" TS phone plug or
jack (See Figure C). Connect the signal to the
center post and the ground (earth) or shield
to the surrounding “basket.”
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 usu-
ally 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)
“tip”
This plug connects to one of the
mixer’s Channel Insert jacks.
“ring”
tip
ring
sleeve
SEND to processor
RETURN from processor
(TRS plug)
Figure F
