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| JL Audio - MHD600/4 Owner’s Manual
15
Speaker loads below 1.5Ω nominal per channel
in stereo or 3Ω nominal in bridged mode are
not recommended and may cause the amplifier
output to distort excessively.
bridging Considerations
Bridging is the practice of combining the
output of two amplifier channels to drive a single
load. When bridged, each channel produces
signals of equal magnitude, but opposite polarity.
The combined output of the two channels
provides twice the output voltage available from a
single channel. The MHD600/4 has been
designed for bridging of its channel pairs without
the need for input inversion adaptors.
Rear
Preouts
Remote
Level
Control
Front
Inputs
L
R
L
R
+12 VDC Ground Remote
To bridge a pair of channels, use the “Left +”
and “Right –” speaker connectors only
(the “Left –” and “Right +” remain unused).
Then connect a mono signal to both left and
right RCA inputs for that channel pair. This
requires an RCA “Y-Adaptor” (sold separately),
because a bridged pair of channels requires that
both amplifier channels of the bridged pair
receive input. Connection of only one RCA input
will result in reduced power output, increased
distortion and can cause the amplifier to overheat.
When bridged, each channel pair will
deliver optimum power into a 3-8Ω load.
Operating bridged channel pairs into a load
lower than 3Ω is not recommended.
speaker Connector Plugs
To connect the speaker wires to the amplifier,
unplug the speaker connector plugs from the
amplifier chassis (pull back firmly) and back out
the set screws on each connector plug, using the
supplied 2.5 mm hex wrench. Strip 3/8 inch (10
mm) of insulation from the end of each wire and
insert the bare wire into the receptacle on the
speaker 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.
When connected to the amplifier, the HD-RLC
operates as follows. At full counter-clockwise
rotation, the audio will mute completely. At full
clockwise rotation the level will be the same as if
the HD-RLC was not connected at all. In other
words, it operates strictly as a level attenuator.
Depending on the application, you may want
the HD-RLC to only affect one channel pair or
both channel pairs. A switch labeled “Remote
Level Control” in the “General Setup” Section
of the Control Panel allows you to determine
whether the HD-RLC affects the level of all
channels “All Ch.” or only the rear channels
“Rear Ch.”
For example, if you are using the MHD600/4
in a stand-alone bi-amplified mode, you may
want the HD-RLC to only affect the level of the
subwoofer channels. Setting the “Remote Level
Control” switch to the “Rear Ch.” position
accomplishes this (provided the subwoofer system
is connected to the rear channels).
In other cases, you may want control of all
four channels at the same time, so you would
set the “Remote Level Control” switch to the
“All Ch.” position.
The RBC-1 Remote Bass Control used with
JL Audio Slash, Slash v2, e-Series, A-Series and
G-Series amplifiers is NOT compatible with the
MHD Series amplifiers. If you attempt to
connect an RBC-1 to an MHD amplifer, the
control will not work. You must use the
HD-RLC controller.
sPeaker outPuts
The MHD600/4 employs JL Audio’s exclusive
Regulated, Intelligent Power Supply (R.I.P.S.)
design. The operation of the R.I.P.S. system is
independent for each pair of channels. This
sophisticated power supply allows the amplifier to
produce its optimum power (150 watts x 4) over a
wide range of speaker impedances.
Rear
Preouts
Remote
Level
Control
Front
Inputs
L
R
L
R
+12 VDC Ground Remote
Unlike conventional amplifiers that require
a specific impedance to produce optimum
power, the R.I.P.S.-equipped MHD600/4 gives
you the freedom to use a variety of speaker
configurations that achieve final nominal
impedances between 1.5 – 4Ω per channel in
stereo (without sacrificing power output or sound
quality). When bridged, each channel pair will
optimize output at 300 watts between 3 – 8Ω.
The operation of the R.I.P.S. circuitry is
entirely automatic and adjusts itself every time the
amplifier is turned on. There are no user controls
to configure. The system operates through
multiple stages of impedance optimization,
choosing the stage most appropriate to the actual
impedance of the speakers you connect to it.
If you connect a load higher than 4Ω nominal
per channel in stereo mode (or 8Ω in bridged
mode), power will drop by half with every
doubling of impedance above 4Ω stereo / 8Ω
mono. If you connect a load lower than 1.5Ω
nominal per channel in stereo mode (or 3Ω in
bridged mode, the amplifier protection
circuitry activates a “safe” mode which reduces
amplifier power to protect the circuitry from
failure (the LED status indicator on the control
panel will light up amber to indicate that this
has happened). See page 16 for details.
