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| JL Audio - MHD900/5 Owner’s Manual
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Many vessels employ small (10 AWG - 6 AWG)
wire to ground the battery to the vessel chassis
and to connect the alternator’s positive
connection to the battery. To prevent voltage
drops, these wires should be upgraded to 4
AWG pure copper wire when installing amplifier
systems with main fuse ratings above 60A.
turn-on wire
The MHD900/5 uses a conven12V
remote turn-on wire, typically controlled by
the source unit’s remote turn-on output. The
amplifier will turn on when +12V is present at
its
“Remote”
input and turn off when +12V is
switched off. If a source unit does not have a
dedicated remote turn-on output, the amplifier’s
turn-on lead can be connected to +12V via a
switch that derives power from an ignition-
switched circuit.
The MHD900/5’s
“Remote”
turn-on connector
is designed to accept 18 AWG – 12 AWG wire. 18
AWG is more than adequate for this purpose.
To connect the remote turn-on wire to the
amplifier, first back out the set screw on the
bottom of the Power Connector Plug, using the
supplied hex wrench. Strip 1/2 inch (12mm) of
wire and insert the bare wire into the receptacle,
seating it firmly so that no bare wire is exposed.
When using smaller wire, it may be necessary to
strip 1 inch of insulation from the wire and fold
the bare wire in half prior to insertion. While
holding the wire in the terminal, tighten the
set screw firmly using the supplied 2.5 mm hex
wrench, taking care not to strip the head of the
screw and making sure that the wire is firmly
gripped by the set screw.
amplifier Power Connector Plug
To connect the power wires and the remote
turn-on wire to the amplifier, unplug the power
connector plug from the amplifier chassis (pull
back firmly) and back out the set screws on
the connector plug, using the supplied 4 mm
hex wrench for the
+12 VDC”
and
“Ground”
connections and the supplied 2.5 mm hex wrench
for the
“Remote”
connection. Strip 3/8 inch (10
mm) of insulation from the end of each wire and
insert the bare wire into the receptacle on power
connector plug, seating it firmly so that no bare
wire is exposed. While holding each wire in place,
tighten each set screw firmly, taking care not to
strip the head of the screw.
Never make power connections with a “live”
wire. Always disconnect the negative battery
post before making any connections or
adjustments to a 12V power connection!
Power and turn-on ConneCtions
Before installing the amplifier, disconnect the
negative (ground) wire from the vessel’s battery.
This will prevent accidental damage to the system,
the vessel and your body during installation.
+12V battery Connection
You will need to connect a power wire to
the vessel’s positive battery terminal, using an
appropriate power ring or specialized battery
terminal connector, such as the JL Audio
XB-BTU. This connection must be tight and
corrosion-free to ensure proper connectivity. This
wire MUST be fused appropriately for safety. Any
positive power wires run through metal barriers
, must be protected with a high quality insulating
grommet to prevent damage to the insulation
of the wire. Failure to do so may result in a
dangerous short circuit.
Power wire requirements
The MHD900/5’s
“+12 VDC”
and
“Ground”
connections are designed to accept 4 AWG
power wire. 4 AWG pure copper wire is
the minimum recommended wire size for
this amplifier. Use of smaller gauge wire
(including cheap wire that is fraudulently sold
as 4 AWG wire) can create a fire hazard.
If you are installing the MHD900/5 with other
amplifiers and wish to use a single main power
wire, use 2 AWG or 1/0 AWG pure copper wire
as a main power wire. This 2 AWG or 1/0 AWG
power wire should terminate into a distribution
block mounted as close to the amplifiers as
possible and should connect to the MHD900/5
with 4 AWG pure copper power wire, with
each smaller wire fused appropriately for each
amplifier or other electronics in the system.
Please note that lower AWG numbers mean
bigger wire and vice-versa (1/0 AWG is the largest,
2 AWG is smaller, then 4 AWG, then 8 AWG, etc.).
We do not recommend the use of “copper-clad
aluminum wire” or “CCA” wire because this
wire is significantly less conductive than pure
copper wire. Only use pure copper power wire,
such as JL Audio’s MetaWire™. Tinned copper
wire (silver color) is acceptable as the tin-plating
is only a very minor component of the wire.
Fuse requirements
The installation of a fuse on the main power
wire, within 18 wire inches (45 cm) of the positive
battery terminal is vital to protect the wire and
the vessel from fire in the event of a collision
or short-circuit. The fuse value at each power
wire should be just high enough for all of the
equipment being run from that power wire. Do
not use a fuse with a value that far exceeds the
total fuse rating of the electronics connected to
the wire.
If only the MHD900/5 is being run from
a single power wire, install a 60A fuse to
protect the wire: AGU (big glass fuse). AFS
(small blade fuse) or MaxiFuse™ (big plastic-
body fuse) types are recommended.
If other amplifiers are also being powered from
a main power wire and exceed 80 amps in total
fuse rating, we recommend the use of an ANL
(large-blade) fuse and holder. Each amplifier can
then be fused independently at the outputs of
the power distribution block. Use JL Audio part
XC-FOA-2PAK and appropriate MaxiFuse™ type
fuses with JL Audio distribution blocks.
Please consult with your JL Audio
dealer to make sure that the wire, fuse
holder and fuse ratings are appropriate
for your system’s needs. The safety of
your installation depends on appropriate
power connections and fuse protection.
ground Connection
The ground connection should be made using
the same gauge wire as the power connection.
It is common for the alternator to be grounded
through its chassis. If the alternator is not
grounded through its chassis and instead employs
a small (10 AWG - 6 AWG) wire to connect to
ground, this wire should also be upgraded to 4
AWG when installing amplifier systems with main
fuse ratings above 60A.
