14 | JL Audio - RD400/4 Owner’s Manual
APPENDIX A:
Input Sensitivity Level Setting
Follow the steps below to adjust the input
sensitivity of each amplifier channel pair, simply
and easily, in just a few minutes to achieve overall
system balance.
Necessary Equipment
• CD with a sine-wave test tone recorded at
0 dBfs 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.).
If your OEM source unit is not equipped with
a CD player, you may transfer the test tone to
a portable media player or thumb drive and
connect to your source unit’s auxiliary input.
Make sure to disable any EQ/DSP modes on
your portable media player during level setting.
The Seven-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 RD400/4).
3) Set the “Input Voltage” switch to “Low”. Turn
both “Input Sensitivity” 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) 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 each channel pair
RD400/4) at 3/4 source unit volume.
6) Slowly increase the “Input Sensitivity”
control until the “Clipping” LED is solidly lit,
indicating maximum, unclipped output. If the
“Clipping” LED is solidly lit with the “Input
Sensitivity” control turned all the way down,
set the “Input Voltage” switch to the “High”
position, then slowly increase the “Input
Sensitivity” control until the “Clipping” LED
is solidly lit.
7) Once you have adjusted each channel section
on the RD400/4 to its maximum, unclipped
output level, reduce the source unit’s volume
to prevent sudden output bursts and reconnect
the speaker(s). Play music and adjust the “Input
Sensitivity” controls downward if the amplifier
requires attenuation to achieve the desired
system balance.
Do not increase any “Input Sensitivity” 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
Sensitivity” if any equalizer boost is activated
after setting the “Input Sensitivity” 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.
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