JL Audio JD 400/4 Owner's Manual page 9

1) "Filter Mode" Controls: The JD400/4
employs 12 dB per octave filters for each
pair of channels. Each of these filters can be
controlled or defeated completely by way of the
three-position "Filter Mode" switches in each
Channel Section:
"Off": Defeats the filter completely, allowing
the full range of frequencies present at the
inputs to feed these channels. This is useful for
systems utilizing outboard active crossovers
or requiring full-range reproduction from this
channel pair.
"LP" (Low-Pass): Configures the filter to
attenuate frequencies above the indicated filter
frequency, at a rate of 12 dB per octave. This
is useful for connection of subwoofers to one
or more of the JD400/4's channel pairs in a
bi-amplified system.
"HP" (High-Pass): Configures the filter to
attenuate frequencies below the indicated filter
frequency at a rate of 12 dB per octave. This is
useful for connection of component speakers
or coaxials to one or more of the JD400/4's
channel pairs in a bi-amplified system.
2) "Filter Freq. (Hz)" The filter frequency
markings surrounding these rotary controls
(one in each Channel Section) are for reference
purposes and are generally accurate to within
1/3 octave or better.
Tuning Hint: If you are using the JD400/4
to drive a subwoofer system ("LP" mode), a
component satellite speaker system ("HP" mode)
or both, 80 Hz is a good baseline "Filter Freq.
(Hz)" setting. After properly adjusting the "Input
Sens.", as outlined in Appendix A (page 14), you
can fine tune the "Filter Freq. (Hz)" control to
achieve the desired system frequency response.
JD400/4
PREOUTS
The JD400/4 includes a buffered, pass-through
preamp output section, so that additional
amplifiers can be easily added to the system. The
preamp output delivers the same signal that is
connected to the amplifier's CH. 1&2 inputs.
INPUT SECTION PREOUTS
CH. 1&2 CH. 3&4 CH. 1&2 (only)
Note: The preamp output signal is not affected by
the amplifier's filter controls. If the input signal is
full-range, the preamp output will be full-range.
Note: When the "Input Voltage" switch is in its
"Low" position, the level of the "Preouts" signals
matches the input signal levels (unity gain).
When the "Input Level" switch is in the "High"
position, the level of the input signal is attenuated
–12 dB to produce a line level signal at the
"Preouts". This ensures a proper line level signal
output under both conditions.
If you plan to use the "Preouts" to feed a stereo
amplifier, you must connect a stereo signal to
the inputs of the amplifier. A mono signal into
the amplifier will result in a mono signal out of
the preamp output.
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