5 SIGNAL
CONNECTIONS
5.1
Input connections
M3 inputs are on female XLR-type connectors and are electronically
balanced. Pin 1 is normally open circuit but may be linked to Ground
(chassis earth) or Lift (signal 0V) by positioning jumper links on the main
PCB (
J1,J2
).
The signal is always applied between pin
2
(hot +) and pin
3
(cold -).
Always use 2-core plus screen ‘balanced’ type signal cable, even for
unbalanced circuits. The screen should be regarded as separate from the
signal return, even if they are connected together at one end of the cable.
Cable lengths longer than 3 metres should be avoided for unbalanced
connections.
For either balanced or unbalanced operation, always connect the input
signal between Pins 2 and 3. The input cable screen should be derived
from the equipment which is sourcing the input provided that normal safety
requirements are met (i.e. the mains earth is connected correctly).
5.2
Output connections
M3 outputs are electronically balanced auto-compensating via male XLR
type connectors. Pin
1
can be configured to be open circuit or lifted
(signal 0V). The output signal appears between Pins
2
and
3.
Always use 2-core plus screen ‘balanced’ type signal cables, even for
unbalanced circuits. The cable screen should be regarded as separate
from the signal return, even if they are connected together at one end.
This is to keep the screen a true screen so that signal return currents do
not flow through it, which can induce signals in adjacent cables
For unbalanced use, whichever pin you have designated to be hot (+)
connect the corresponding cold pin (-) and Pin 1 together. The internal
output signal grounds
J3, J4, J5,
and
J6
should be placed in the open
circuit position which allows the amplifier to be locally grounded (as
required for safety reasons) without causing a hum loop. If the signal is
taken between Pin
2
or
3
and Pin
1
a level loss and signal degradation will
occur. When using unbalanced connections avoid cable lengths greater
than 3 metres.
For balanced operation, the screen should be connected at the amplifier
end. To eliminate hum current loops jumpers
J3, J4, J5
and
J6
can be
placed in the open circuit position.
The power ratings of amplifiers connected to the M3 controller should lie
within the range recommended for the Blackline series of loudspeakers
being used. Please refer to the section on amplification for further
information.
Martin Audio – M3 System Controller
E
NGLISH
4
CONTENTS
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GUIDES
