User Guide

SYSTEM CONFIGURATIONS
The 300/4 is a flexible amplifier, well-suited for a
multitude of system configurations. In this section, the
most likely configurations are explained in detail.
Once you have selected your desired
configuration, you can use the amplifier panel
drawings on the bottom of the following
pages to mark the required switch positions for
easy reference.
BI-AMPLIFIED SYSTEMS
Bi-amplified systems are defined as systems in
which separate amplifier channels drive low-
frequency (LF) and high-frequency (HF) speakers and
are separately filtered to send appropriate frequency
ranges to each speaker system.
The most common application of bi-amplification
in mobile audio is to drive a subwoofer system from
one or more amplifiers or channels and component
speakers from separate amplifiers or channels.
The 300/4 can be configured to drive a bi-
amplified system by itself or with a separate
subwoofer amplifier.
BI-AMPLIFIED SYSTEM WITH ONE 300/4
In this configuration, the rear channels of the
300/4 will drive subwoofers (stereo 75W x 2 or
bridged 150W x 1) with low-pass filtering.The front
channels will drive component speakers in stereo
(75W x 2) with high-pass filtering.
Input connection options for a bi-amplified system
with one 300/4 are as follows:
A) No User Adjustability
Required: a basic source unit or processor with left
and right stereo outputs.
Input Connections: a single pair of stereo source
unit outputs connected to the front channel inputs
of the 300/4 (select “2ch” on the “Input Mode”
switch in the “Front Input Section”).
Result: the relative level of the LF and HF
channels will be fixed by the 300/4’s “Input Sens.”
settings and will not be user adjustable from the
front of the vehicle.
B) Fade Subwoofer Level vs. HF Level
Required: a source unit or processor with front and
rear pairs of outputs.
Input Connections: the first stereo pair of source
unit outputs is connected to the front inputs of the
300/4.The second stereo pair of source unit
outputs is connected to the rear inputs (select
“4ch” on the “Input Mode” switch in the “Front
Input Section”).
Result: in this mode, the user has the ability to fade
or control the level of the LF channels relative to
the HF channels via the source unit’s fader control
without exceeding the maximum clean output level
set by each amplifier section’s “Input Sens.” controls.
C) Subwoofer Level Control Only
Required: a source unit or processor with left, right
and subwoofer outputs.
Input Connections: the main stereo pair of source
unit outputs is connected to the front inputs of the
300/4.The source unit’s dedicated subwoofer
output is connected to the rear inputs (select “4ch”
on the “Input Mode” switch in the “Front Input
Section”).
Result: in this mode, the user has the ability to
control the absolute level of the LF channels relative
to the HF channels.
Set the rear channel “Input Sens.” with the
source unit’s subwoofer level control set at 3/4 of full
output. See Appendix B (page 14) for details.
IMPORTANT
!
JL AUDIO 300/4 11
STATUS INDICATOR LIGHTS /
PROTECTION CIRCUITRY
There are three status indicator lights on the top
of the amplifier. These are as follows:
1) “Power” (Green): lights to indicate that the
amplifier is turned on and operating normally.
2) “Thermal” (Red): lights to indicate that the
amplifier has exceeded its safe operating
temperature, putting the amplifier into a self-
protection mode, which reduces the power
output of the amplifier. The red light will shut off
and the amplifier will return to normal, full-power
operating mode if the heat sink temperature
drops back to a safe level.
3) “Low Ω” (Amber): lights to indicate that the
impedance of the speaker load connected to the
amplifier is lower than the optimum load impedance
range for the amplifier. When this light is on, a
protection circuit engages and reduces the power
output of all four amplifier channels.The amber
indicator will also light when a short-circuit is
detected in the speaker wiring (this can be a short
between the positive and negative speaker wires or
between either speaker wire and the vehicle
chassis).This can be used to diagnose a short-circuit
by only connecting one of the amplifier sections at a
time (front or rear).The amber LED will light when
you connect the section that is experiencing the
problem and turn the volume up.
There is only one condition that will shut
down an undamaged 300/4 completely…
If battery voltage drops below 10 volts, the entire
amplifier will shut itself off.The green “Power”
indicator on the top of the amplifier will turn off
when this occurs.The amplifier will turn back on
when voltage climbs back above 10 volts.This may
happen in a rapid cycle when bass-heavy program
material causes a weak charging system to dip
below 10 volts momentarily. If this is happening in
your system, have your charging system inspected to
make sure it is working properly. A 0.5 or 1.0 Farad
rapid-discharge capacitor connected in parallel to
the amplifier power connections will minimize these
short duration voltage dips in most systems that are
having this problem.
For information on troubleshooting this
amplifier, refer to Appendix C (page 18).
SERVICING YOUR JL AUDIO AMPLIFIER
If your amplifier fails or malfunctions, please
return it to your authorized JL Audio dealer so
that it may be sent in to JL Audio for service.
There are no user serviceable parts or fuses
inside the amplifier.The unique nature of the
circuitry in the JL Audio amplifiers requires
specifically trained service personnel. Do not
attempt to service the amplifier yourself or
through unauthorized repair facilities.This will not
only void the warranty, but may result in the
creation of more problems within the amplifier.
If you have any questions about the installation or
setup of the amplifier not covered in
this manual, please contact your dealer or the
JL AUDIO Technical Department for assistance:
[phone]
9:00 AM – 5:30 PM Eastern Time,
Monday – Friday
10 JL AUDIO 300/4