Macro-Tech 24x6 Reference Manual - page 12
Page 12
Macro-Tech 24x6 & 36x12 Power Amplifiers
3.3.1 Input Connection
Both the balanced XLR and phone jack inputs have a
nominal impedance of 20 K ohms (10 K ohms with un-
balanced wiring) and will accept the line-level output
of most devices. Female XLR input connectors are pro-
vided on the standard P.I.P.-FX input module (other
P.I.P. modules are described in Section 8.1). Correct
input wiring will depend on two factors: (1) whether the
input signals are balanced or unbalanced, and (2)
whether the signal source floats or has a ground refer-
ence. Figures 3.7 and 3.8 show the recommended
connection techniques for each type of signal source.
The amplifier’s built-in ¼ inch input phone connectors
can be wired similarly for balanced or unbalanced,
floating or ground-referenced sources. The connectors
Twin-lead shielded cable
2-wire line cord
(or battery power)
Shield connected
to ground terminal
3-wire grounded line cord
(or other ground connection)
Shield is not
connected
at this end
Grounded
source
3-wire grounded line cord
(or other ground connection)
Input ground
terminal not used
Grounded
source
Single-conductor coax
or twisted pair
2-wire line cord
(or battery power)
Floating
source
Shield connected to both
negative (–) and ground
input terminals
+
–
INPUT
Output
Floating
source
+
3
1
2
+
–
INPUT
+
Output
3
1
2
+
–
INPUT
Output
+
3
1
2
+
–
+
Output
INPUT
3
1
2
Fig. 3.5 Unbalanced Input Wiring
Fig. 3.7 Balanced and Unbalanced Phone Plug Wiring
have a standard tip-ring-sleeve (TRS) configuration:
the tip is positive (+), the ring is negative (–) and the
sleeve is ground (see Figure 3.7). Wiring for various
sources follows the XLR wiring guidelines shown in Fig-
ures 3.5 and 3.6.
The phone jacks should not be used as inputs when a
P.I.P. module with active circuitry is installed. The phone
jacks are in parallel with the output of the
P.I.P. module,
so an input signal connected to the phone jacks can
feed backwards into the active circuitry of the
P.I.P. and
cause undesirable distortion. You can use the phone
jacks for signal input with any of the following
P.I.P.
modules installed: P.I.P.-FX, P.I.P.-BB, P.I.P.-FMX, P.I.P.-
FXQ and P.I.P.-FPX. All other
P.I.P. modules have active
circuitry and should not be installed if you plan to con-
nect input signals to the phone jacks. The phone jacks
can always be used as “daisy chain” outputs to feed
post-processed signals from the
P.I.P. to the inputs of
other amplifiers.
3
1
2
+
–
INPUT
2-wire line cord
(or battery power)
Note: If two or more channels with
the same input ground reference
are driven from the same
floating source, connect
only one shield to the
source chassis.
Floating
source
3-wire grounded line cord
(or other ground connection)
Shield not connected
at this end
Grounded
source
3
1
2
Output
+
–
+
–
Output
+
–
INPUT
Fig. 3.6 Balanced Input Wiring
+
–
SHIELD
BALANCED
+
SHIELD
UNBALANCED