12
JL Audio
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
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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 speakers from the
amplifier’s speaker output connectors (you need
only disconnect one wire on each output).
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.
3)
Turn the
“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 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
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a track with an appropriate sine wave
(within the frequency range to be
amplified) at 3/4 source unit volume.
7)
Connect the AC voltmeter to the speaker output
connectors of the amplifier. Make sure you test
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8)
Increase the
“Input Sens.”
control until the
target voltage is observed with the voltmeter.
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 RTA 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.
Nom.
Impedance
Target AC Voltage
Stereo
Bridged
8Ω
15.5 V
31 V
6Ω
15.5 V
28 V
4Ω
15.5 V
25 V
3Ω
14 V
not recommended
2Ω
12.5 V
not recommended
