4-Channel Full-Range Amplifier:
The JL Audio XD400/4 is a four-channel, full-range audio amplifier utilizing
NexD ultra-high speed switching technology to deliver outstanding fidelity and
efficiency. The XD400/4 can be operated with a wide variety of source units and
Amplifier Rating: The JL Audio XD400/4 Class D
4-channel amplifier is rated at 75 Watts RMS x 4-channels in
4-ohm at 20 to 20,000Hz with a signal-to-noise-ratio of 104 dB and a total
harmonic distortion of 1% while receiving 14.4 Volts.
NexD Class D Technology: NexD is a state-of-the-art switching
amplifier design that combines exceptional audio quality with excellent
efficiency and less complexity. This results in an affordable compact
amplification with exceptional audio quality and unsurpassed total efficiency.
Advanced Rollback Protection: The XD-Series amplifiers employ advanced
thermal and low-impedance protection to virtually eliminate annoying amplifier
shut-down events. Should any XD-Series amplifier ever overheat, its intelligent,
unregulated power supply reacts by limiting available peak voltage until the
amplifier returns to a safe temperature range. Likewise, if an impedance lower
than optimal for the amplifier is present at the outputs, the XD amplifier will
roll back peak voltage to protect itself without shutting down.
Differential-Balanced Inputs: The JL Audio amplifier features
differential-balanced input architecture to effectively control noise and ensure
compatibility with a wide variety of source units, including many OEM
systems. Without resorting to line output converters, you can directly connect
most OEM source units to the JL Audio amplifier without creating any noise or
compatibility issues. Unlike conventional single-ended inputs, the
differential-balanced design does not connect one side of the audio signal to
chassis ground. This eliminates any voltage sensitivity between one input
terminal and ground and greatly reduces the incidence of alternator whine in a
typical car audio installation.
Note: You will need two speaker wire to RCA adaptors (136XDCLR2S,
sold separately) to connect this amplifier to your headunit via speaker-level.
Protection Circuitry With Status Indicator Lights: There is
a single multi-color LED on the top panel of the amplifier to indicate the
amplifier's operating status.
- Flashing Green: When
the LED is flashing green, the amplifier is powering up and audio output is
- Constant Green: This LED lights green to indicate that the
amplifier is turned on and operating normally.
- Constant Red: This Red LED 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.
- Constant Amber (Yellow): The Amber (Yellow) LED light indicates that an over-current condition has occurred and is accompanied by a muting of the amplifier's output.
Over-current condition can be caused by a speaker inpedance lower than the
optimum load impedance range for the amplifier or a short-circuit in the
- LED Off: The only condition that will shut down an undamaged
XD400/4 completely is if battery voltage or remote turn-on voltage drops
below 10-volts. The amplifier will turn back on when voltage climbs
back above 11-volts.
Cooling System: The outer shell of the JL Audio amplifier is designed
to remove heat from the amplifier circuitry. For optimum cooling performance,
this outer shell should be exposed to as large a volume of air as possible.
Enclosing the amplifier in a small, poorly ventilated chamber can lead to
excessive heat build-up and degraded performance.
Control Panel Cover: The
XD400/4 features a Control Panel Security Cover which protects and hides the
amplifier's controls. When installed, the cover ensures that the amplifier's
settings are not accidentally changed while creating a clean aesthetic look for
the amplifier and your installation. The control panel security cover is
pre-installed at the factory and must be temporarily removed for access the
amplifier's controls. The security cover is secured by two 2.5mm hex-head
Simplified Gain Setting: The XD Series amplifier makes
setting the gain level of the amp via the input sensitivity control very simple.
All you need is Digital AC Voltmeter (142TK12V, sold separately) and a Test CD Disc (503CD104,
sold separately) 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).
Note: The XD400/4 is equipped with a independent gain controls for
the Front (1&2) and Rear (3&4) channels.
Flexible Input Section And Active Crossover Network: The JL
Audio XD amplifier provides a flexible input section and a comprehensive
crossover network to fine tune your system effectively and accurately. The
variable filter design employed in the JL Audio XD amplifier crossover sections
allow you to seamlessly switch slopes, easily change filter frequencies and
address what frequencies the preamp inputs will pass. The XD400/4 offers the
following independent crossover adjustments for the front and rear channels
along the unit's top panel, behind a removal cover plate.
- Input Mode: This switch allows operation of all four
amplifier channels with only one pair of input signals (2-CH Input Mode) or
with independent front and rear input signal pairs (4-CH Input Mode). You
will only need to connect the front RCA inputs when placing the amplifier in
2-CH input mode.
- Filter Mode: The amplifier allows you to select either
a Low Pass, High Pass or Full-Range operation of the amplifier's 1 & 2
channels and 3 & 4 channels.
- Variable Frequency: You can set the amplifier's Low
Pass or High Pass crossover from 50 to 200 Hz for channels 1 & 2 and
channels 3 & 4.
The amplifier features set-screw terminals for the power, ground, and remote
- Power and Ground:
The JL Audio amplifier's set-screw Power and Ground
connections are designed to accept 8 to 4 AWG power wire.
A 2.5mm hex-wrench is supplied for making connections.
- Remote Turn-On: The JL Audio XD amplifier's set-screw turn-on lead
accept 18 to 8 AWG wire. The same 2.5mm hex-wrench is supplied for making
Note: The Amplifier is not equipped with a fuse. An
external 40-amp AFS, AGU, or MAXI fuse (not included) must be installed on
the power wire. If a wiring kit is used which includes a fuse with a value
other than 40-amps, the original should be replaced with a 40-amp fuse
Speaker Output Terminals: The XD400/4 amplifier's eight
set-screw speaker terminals will accept 16 to 8 AWG speaker wire. A 2.5mm
hex-wrench is supplied for making connections.
Preamp Inputs: The amplifier features two sets of
differential-balanced RCA jack inputs. The amplifier features a dedicated Input
Sensitivity gain control for the front and rear channels of the amplifier. These
controls are designed to match the input sensitivity of the XD400/4 to the
specific signal source that is feeding it. The amplifier's input level can be
set independently for the front and rear channels between 100mV-4V.
Preamp Outputs: The XD400/4 incorporates a pass-through
preamp output sections, so that additional amplifiers can easily be connected to
the same signal(s) feeding the XD400/4. These preamp output signals are buffered
to prevent noise and are always preamp level, regardless of the level of signals
feeding the XD400/4's inputs. The amplifier's set of preamp outputs can be
configured two different ways.
- Front (1&2): The preamp output delivers the same
signals that is connected to the XD400/4's front RCA inputs. This mode is
useful for feeding a subwoofer amplifier when the XD400/4 is being used to
drive front and rear speaker system. In this mode, the preamp output level
will track with the signal level of the front input signals, allowing you to
fade the rear channels in and out, without affecting the subwoofer level.
- Sum (F+R): This mode delivers a sum of the signals
being fed to the front and rear RCA inputs of the amplifier. When the
XD400/4 is being used to drive front and rear speaker systems, this preamp
output mode will deliver a summed front/rear signal to the subwoofer
amplifier, while permitting fading of the front and rear speaker system from
the source unit.
Remote Level Control: The amplifier features a standard
telephone connector for adding an optional wired remote level control. With the
addition of the optional wired Remote Level Control (136HDRLC,
sold separately), you can control the volume of one or both channel pairs of the
XD400/4 form the front of your vehicle. This is useful for subwoofer level
control or even as a master volume control for your system. If desired, multiple
XD amplifiers can be controlled from a single HD-RLC controller using a simple
phone line splitter and multiple phone cables (all sold separately).
Note: All inputs and outputs are located on the rear
side of the amplifier to make installation of the amplifier simple and neat.