JL Audio MHD600/4-24V Owner's Manual page 10

"input Voltage" switch
A wide range of signal input voltages can be
accommodated by each of the MHD600/4-24V's
differential-balanced inputs (200mV – 8V RMS).
This wide range is split up into two sub-ranges,
accessible via the "Input Voltage" switches located
in each input section of the amplifier. Be aware
that each input section's "Input Voltage" switch
will have to be configured, regardless of how many
input cables are actually feeding the amplifier.
The "Low" position on each "Input
Voltage" switch selects an input sensitivity
range between 200mV and 2V. This means that
the "Input Sens." rotary control will operate
within that voltage window. If you are using
an aftermarket source unit, with preamp-level
outputs, this is most likely the position that
you will use (regardless of what voltage output
capability is claimed by the source unit).
The "High" position on the "Input Voltage"
switch selects an input sensitivity range between
800mV and 8V. This is useful for certain high-
output preamp level signals as well as speaker-level
outputs from source units not equipped with
preamp-level outputs.
To use speaker-level sources, splice the speaker
output wires of the source unit or small amplifier
onto a pair of RCA plugs for each input pair
or use the JL Audio ECS Speaker Wire to RCA
adaptor (XB-CLRAIC2-SW).
The output of the amplifier decreases for a
given input voltage when the "Input Range"
switch is placed in the "High" position. The
output increases with the switch in the "Low"
position. While this may sound counter-
intuitive, it is correct as described.
10 | JL Audio - MHD600/4-24V Owner's Manual
"input sens." control
Located next to the "Input Voltage" switch
in each input section is a rotary control labeled
"Input Sens.". Once the appropriate "Input
Voltage" range has been selected, this control
can be used to match the source unit's output
voltage to the input stage of each pair of amplifier
channels for maximum clean output. Rotating the
control clockwise will result in higher sensitivity
(louder for a given input voltage). Rotating the
control counter-clockwise will result in lower
sensitivity (quieter for a given input voltage). To
properly set each pair of amplifier channels for
maximum clean output, please refer to Appendix
C (pages 18, 19) in this manual.
After using this procedure, you can then adjust
the relative level of each channel pair by adjusting
the input sensitivity downward on either or both
channel pairs, if they require attenuation to
achieve the desired system balance.
Do not increase the "Input Sens." setting for
any amplifier in the system beyond the maximum
level established during the procedure outlined in
Appendix C (pages 18, 19). Doing so will result in
audible distortion and possible speaker damage.
Be aware that both "Input Sens." adjustments
will have to be made, regardless of how many
input cables are feeding the amplifier. These
controls will allow you to set the appropriate
relative levels for the "Front" channels relative
to the "Rear" channels and any other amplifier
channels in the system.