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1
⁄4" TS PHONE PLUGS AND JACKS
“TS” stands for Tip-Sleeve, the two connections
available on a “mono”
1
⁄
4
" phone jack or plug (Fig-
ure C). TS jacks and plugs are used in many
different applications, always unbalanced. The tip
is connected to the audio signal and the sleeve to
ground (earth). Some examples:
• Unbalanced microphones
• Electric guitars and electronic instruments
• Unbalanced line level connections
NOTE: All the unbal-
anced
1
⁄
4
" inputs on the
LM-3204 have the ring con-
ductor wired to the shield
(ground), so that you can
plug in a balanced cord with no loss of level.
ANOTHER NOTE: All the unbalanced
1
⁄
4
"
outputs on the LM-3204 implement “imped-
ance balancing”. When you plug a balanced
cord into one of these, both the tip and ring
conductors have equal impedance, significantly
improvings common mode characteristics. In
other words, although unbalanced, a balanced
input receiving this cord will “think” it’s getting
a balanced signal!
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 cir-
cuit, change the input routing of the signal or
serve other functions. The Mackie LM-3204 uses
switches in the channel insert and bus insert
jacks, input jacks, AUX sends and AUX returns la-
beled “(MONO) Left.” See Special Mackie
Connections farther on. 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 circum-
stances where you
are to insert the
plug only partially. Once again, 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. Connect the signal to the center post and
the ground (earth) or shield to the surround-
ing “basket.” Tape In and Tape Out are available
on RCA jacks on the Mackie LM-3204.
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 (earth) will also be
connected to the ground (earth) at the
unbalanced input. If there are hum or radio
frequency 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 spe-
cial adapters to interconnect your equipment. 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 the
Mackie LM-3204 jacks. A
1
⁄
4
" TS plug inserted
into a
1
⁄
4
" TRS balanced input, for example,
will automatically unbalance the input and
make all the right connections. Conversely, a
1
⁄
4
" TRS plug inserted into a
1
⁄
4
" unbalanced in-
put will automatically tie the ring (low or
cold) to ground (earth).
APPENDIX
SLEEVE
TIP
TIPSLEEVE
TIP
SLEEVE
Figure C: TS plug
TIPSLEEVETIPSLEEVE
Figure D: RCA plug