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14 | JL Audio - XD400/4v2 Owner’s Manual
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 for that set of channels
(50 Hz for subwoofer channels, 1 kHz for a
midrange application). Do not use attenuated
test tones (-10 dB, -20 dB, etc.).
The Nine-Step Procedure
1) Disconnect the speaker(s) from the
amplifier’s speaker output connectors.
2) Turn off all processing (bass/treble, loudness,
EQ, etc.) on the source unit, processors (if
used) and amplifier. Set the fader control to
center position and the subwoofer level control
to 3/4 of maximum (if used to feed
the XD400/4v2).
3) Switch the “Input Voltage” switch to “Low”
Turn both “Input Sens.” controls 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 chart 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.
6) Verify that you have disconnected the speakers
before proceeding. Play a track with an
appropriate sine wave (within the frequency
range to be amplified by the XD400/4v2) 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.
9) Once you have adjusted each channel section
on the XD400/4v2 to its maximum low-
distortion output level, reconnect the speaker(s).
The “Input Sens.” controls can now be adjusted
downward if the amplifier requires attenuation
to achieve the desired system balance.
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.” 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.
Nom.
Impedance
Target AC Voltage
Stereo Bridged
8
17.3 V 34.6 V
4
17.4 V 28.2 V
2
14.1 V not recommended
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