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APPENDIX A:
Input Sensitivity Level Setting
Following the directions below will allow the
installer to adjust the input sensitivity of each
amplifier channel pair simply and easily in just a
few minutes using equipment which is commonly
available in installation bays.
Necessary Equipment
• Digital AC Voltmeter
• CD with a sine-wave test tone recorded at
0 dB reference level in the frequency range
to be amplified (50 Hz is a good choice). Do not
use attenuated test tones (-10 dB, -20 dB, etc.).
The Nine-Step Procedure
1) Disconnect the subwoofer(s) from the
amplifier's subwoofer output connector (you
need only disconnect Pos. or Neg., not both).
2) Turn off all processing (bass/treble, loudness,
EQ, etc.) on the source unit, processors (if
used) and amplifier. Set the source unit's fader
control to center position and its subwoofer level
control to 3/4 of maximum. If connected, set the
amplifier's Remote Level Control at maximum
(full clockwise).
3) Turn the amplifier's "Input Sens." control all
the way down.
4) Set the source unit volume to 3/4 of full
volume. This will allow for reasonable gain
overlap with moderate clipping at full volume.
5) Using the charts on this page, determine the
target voltage for input sensitivity adjustment
according to the nominal impedance of the
speaker system connected to the amplifier
outputs. Make sure you reference the appropriate
chart for your specific JX monoblock model.
6) Verify that you have disconnected the speakers
before proceeding. Play a track with an
appropriate sine wave (50 Hz is recommended)
at 3/4 source unit volume.
7) Connect the AC voltmeter to the speaker output
connectors of the amplifier. Make sure you test
the voltage at the correct connectors (+ and –).
8) Increase the "Input Sens." control until the
target voltage is observed with the voltmeter.
12
9) Once you have adjusted the amplifier to
its maximum low-distortion output level,
reconnect the speaker(s) and listen to the
system. The "Input Sens." controls can
now be adjusted downward if the amplifier
requires attenuation to achieve the desired
system balance.
I M P O R TA N T !
Do not increase any "Input Sens." setting for
any amplifier channel or channel pair in the
system beyond the maximum level established
during this procedure. Doing so will result in
audible distortion and possible speaker damage.
It will be necessary to re-adjust the
"Input Sens." for the affected channels if any
equalizer boost is activated after setting the
"Input Sens." with this procedure. This applies
to any EQ boost circuit, including source unit
tone controls or EQ circuits. EQ cuts will not
require re-adjustment.
JX250/1D
Nom. Impedance
4Ω
3Ω
2Ω
JX500/1D
Nom. Impedance
4Ω
3Ω
2Ω
JX1000/1D
Nom. Impedance
4Ω
3Ω
2Ω
Target AC Voltage
25.3 V
24.5 V
22.4 V
Target AC Voltage
34.6 V
35.5 V
31.6 V
Target AC Voltage
44.7 V
47.4 V
44.7 V
JL Audio
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