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I M P O R TA N T
The output of the amplifier will decrease
for a given input voltage when the "Input
Range" switch is placed in the "High" position.
Conversely, the output will be higher with
the switch in the "Low" position. While this
may sound counter-intuitive, it is correct
as described.
Preamp Output Section
Infrasonic Filter
Output Mode
Filter Slope
Mode
3) Input Sensitivity Adjustment: Located
l Range | Amp Filter | Out Filter
12dB | 24dB
Off | On
next to the "Input Voltage" switch, in the
65
30
Filter Mode
"Amplifier Input Section", is a rotary control
55
80
22
45
45
100
18
55
labeled "Input Sens.". Once the appropriate
LP | HP
40
200
15
60
"Input Voltage" range has been selected, this
Left Output
Right Output
Filter Freq. (Hz)
Infrasonic Freq. (Hz)
rotary control can be used to match the source
unit's output voltage to the input stage of the
amplifier 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 the amplifier
for maximum clean output, please refer to
Appendix A (page 14) in this manual. After
using this procedure, you can then adjust
the level of the amplifier by adjusting the
input sensitivity downward, if the amplifier
requires 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 A (page
14). Doing so will result in audible distortion
and possible speaker damage.
CrossoVer Controls
Crossovers are groups of individual electronic
filters which allow only certain frequency
ranges to pass through them by attenuating
frequencies outside the selected range. These
filters allow the user to specify what frequency
range will be sent out of each channel section
of the amplifier. This, in turn, allows each
speaker system to only reproduce a range of
frequencies it is well-suited for, resulting in
reduced distortion and improved fidelity.
8 | JL Audio - 1200/1
Owner's Manual
v3
amPliFier low-Pass Filter
The 1200/1v3 employs a sophisticated, state-
variable, low-pass active filter for its internal
channel. This feature is designed to attenuate
frequencies above its filter frequency, so that the
system's subwoofers do not reproduce any audible
midrange content.
Amp LP Filter
Amplifier Input Section
"Q"
Center Freq.
Boost (dB)
+12VDC
Ground
1.6
40
+10
Mode | Slope
Input Voltage
1.1
2.7
30
60
+4
+13
0.7
25
75
Off | 12dB | 24dB
Low | High
0.5
4.3 20
80
0
+15
65
Bass EQ
55
80
Advanced
Bass
45
100
Control
Off | On
40
200
Remote Bass Port
Filter Freq. (Hz)
Left Ch.
1) Filter Operation: The low-pass filter in the
1200/1v3 is fully variable between 40 Hz and
200 Hz via the "Filter Freq." control knob
and features the ability to select between a
moderate "12dB" per octave or a steep "24dB"
per octave slope via the "Mode/Slope" switch.
Depending on the subwoofer system and the
vehicle, different slopes may be required to
produce a smooth transition to the mid-bass
speakers in the system. Experiment to find
the slope which best matches the acoustic
requirements of your system.
Tuning Hint
A trunk mounted sub whose output
:
has to "fight" through a rear deck or a back seat
often benefits from the 12 dB/octave slope which
lets more upper bass content pass through. A sub
that fires directly into the listening environment
is more likely to benefit from a 24 dB/octave slope.
The above hint is not "set-in-stone"...
You should always listen to the system carefully to
determine the best choice as vehicle acoustics and
other factors play a big role in choosing the most
appropriate filter slope.
2) Precise Frequency Selection: The filter
frequency markings on the front panel of
the amplifier are for reference purposes and
are generally accurate to within 1/3 octave
or better. If you would like to select the filter
frequency with a higher level of precision,
consult Appendix C: Chart A-1 (page 16)
of this manual. This chart gives you a more
Subwoofer Output
Remote
accurate frequency for each of the forty
Input Sens.
Signal Sensing
detented positions of the frequency selection
Off | On
control. This method can be very useful if the
amplifier is mounted in a location where you
MONO OUTPUT ONLY
can't see the front panel markings easily.
Right Ch.
3) Defeating the Amplifier Filter: The Low-
Pass filter can also be defeated completely,
by switching the "Mode/Slope" switch to the
"Off" position. This is useful if you are using
an external active crossover in the system.
Keep in mind that turning the internal
crossover off also defeats the "Advanced Bass
Control" section processing (see page 10 for
details). With the internal crossover turned
off, the 1200/1v3's upper frequency response
limit is 250 Hz, due to its bass-specific
Class D design.
PreamP outPut seCtion
The 1200/1v3 incorporates a flexible preamp
output section, designed to make multiple
amplifier systems easy to set up.
The Preamp output can be configured in three
different "Output Modes":
1) "Full-Range": This is a pass-through mode
for the preamp output, delivering the same
signal that is being fed to the "Amplifier Input
Section" (If the input signal is full-range, the
preamp output will be full-range). This signal is
not affected by the "Advanced Bass Control"
processing selected for the amplifier.
2) "Amp Filter": The preamp output delivers
the same signal that is feeding the 1200/1v3's
amplifier section, including all the processing
induced by the "Amp LP Filter" and
"Advanced Bass Control" sections. This
is primarily used for running additional
1200/1v3's in a "Slave" configuration from the
"Master" amplifier. For detailed information on
"Master/Slave" configurations, see Appendix
D (page 18). If the "Output Mode" switch is
in the "Amp Filter" position and the "Amp
LP Filter" switch is in the "Off" position, there
will be no output from the preamp output
jacks. The independent output filter controls
("Filter Slope", "Filter Freq" and "Filter
Mode") are inactive in "Amp Filter" mode.
9
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