JL Audio XD400-4 User Manual

2.84 Mb

owner’s manual

400W 2/3/4 Channel Amplifier

Thank you for purchasing a JL Audio amplifier for your automotive sound system.

Your amplifier has been designed and manufactured to exacting standards in order to ensure years of musical enjoyment in your vehicle. For maximum performance, we highly recommend that you have your new amplifier installed by an authorized JL Audio dealer. Your authorized dealer has the training, expertise and installation equipment to ensure optimum performance from this product. Should you

decide to install the amplifier yourself, please take the time to read this manual thoroughly so as to familiarize yourself with its installation requirements and setup procedures.

If you have any questions regarding the instructions in this manual or any aspect of your amplifier’s operation, please contact your authorized JL Audio dealer for assistance. If you need further assistance,

please call the JL Audio Technical Support Department at (954) 443-1100during business hours.

Protect Your Hearing!

We value you as a long-termcustomer. For that reason, we urge you to practice restraint in the operation of this product so as not to damage your hearing and that of others in your vehicle. Studies have shown that continuous exposure to high sound pressure levels can lead to permanent (irreparable) hearing loss. This and all otherhigh-poweramplifiers are capable of producing such high sound pressure levels when connected to a speaker system. Please limit your continuous exposure to high volume levels.

While driving, operate your audio system in a manner that still allows you to hear necessary noises to operate your vehicle safely (horns, sirens, etc.).

Serial Number

In the event that your amplifier requires service or is ever stolen, you will need to have a record of the product’s serial number. Please take the time to enter that number in the space

provided below. The serial number can be found on the bottom panel of the amplifier and on the amplifier packaging.

Serial Number:

Installation Applications

This amplifier is designed for operation in vehicles with 12 volt, negative-groundelectrical systems. Use of this product in vehicles with positive ground and/or voltages other than 12V may result in damage to the product and will void the warranty.

This product is not certified or approved for use in aircraft.

Do not attempt to “bridge” the outputs of this amplifier with the outputs of a second amplifier, including an identical one.





Ch. 1 & 2

Ch. 1 & 2 Filter

Ch. 3 & 4

Ch. 3 & 4 Filter



Level Mode


Filter Mode


Filter Mode










(pg. 9)

(pg. 6)

(pg. 9)

(pg. 11)

(pg. 8)

(pg. 8)

(pg. 8)

(pg. 8)





Ch. 1 & 2 Input

Ch. 3 & 4 Input





Sensitivity Control

Sensitivity Control






(pg. 7)


(pg. 7)

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Planning Your Installation

It is important that you take the time to read this manual and that you plan out your installation carefully. The following are some considerations that you must take into account when planning your installation.

Cooling Efficiency Considerations:

The outer shell of your 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-upand degraded performance. If an installation calls for an enclosure around the amplifier, we recommend that this enclosure be ventilated with the aid

of a fan. In normal applications, fan-coolingis not necessary.

Mounting the amplifier upside down is strongly discouraged. If mounting the amplifier under a seat, make sure there is at least 1 inch (2.5 cm) of space above the amplifier’s outer shell to permit proper cooling.

Safety Considerations:

Your amplifier needs to be installed in a dry, well-ventilatedenvironment and in a manner which does not interfere with your vehicle’s safety equipment (air bags, seat belt systems, ABS brake systems, etc.). You should also take the time to securely mount the amplifier so that it does not come loose in the event of a collision or a sudden jolt to the vehicle.

Stupid Mistakes to Avoid

Check before drilling any holes in your vehicle to make sure that you will not be drilling through a gas tank, brake line, wiring harness or other vital vehicle system.

Do not run system wiring outside or underneath the vehicle. This is an extremely dangerous practice which can result in severe damage to your vehicle and person.

Protect all system wires from sharp metal edges and wear by carefully routing them, tying them down and using grommets and loom where appropriate.

Do not mount the amplifier in the engine compartment, under the vehicle, on the roof or in any other area that will expose the amplifier circuitry to the elements.




Chassis Ground



Channels 1 & 2

Left & Right Preamp
















Preamp Input Jacks


Output Jacks













(pg. 5)





(pg. 6)




(pg. 9)

Jack for









+12 V Power




Remote Turn-On


Channels 3 & 4


Remote Level

Channels 1 & 2

Channels 3 & 4









Preamp Input Jacks


Control Knob

Speaker Outputs

Speaker Outputs

(pg. 5)





(pg. 6)





(pg. 6)


(pg. 9)

(pg. 10)

(pg. 10)












































































































Product Description

The JL Audio XD400/4 is a four-channel,full-rangeaudio amplifier utilizing JL Audio NexD™ultra-highspeed switching technology to deliver outstanding fidelity and efficiency.

The XD400/4 can be operated with a wide variety of source units and system configurations.

Typical Installation Sequence

The following represents the sequence for a typical amplifier installation, using an aftermarket source unit or OEM Interface processor (like the CleanSweep CL441dsp).

Additional steps and different procedures may be required in some applications. If you have any questions, please contact your authorized JL Audio dealer for assistance.

1) Disconnect the negative battery post connection and secure the disconnected cable to prevent accidentalre-connectionduring installation.This step is not optional.

2) Run power wire from the battery location to the amplifier mounting location. True 8 AWG power wire may be used for runs shorter than 18 ft. For longer runs, use 4 AWG wire. Take care to route the wire in such a way that it will not be damaged and will not interfere with vehicle operation. Use 4 AWG or larger power wire and a power distribution block if additional amplifiers are being installed with the XD400/4.

3) Connect power wire to the positive battery post. Fuse the wire with an appropriate fuse block (and connectors) within 18 inches (45 cm) wire length of the positive battery post.

This fuse is essential to protect the vehicle. Do not install the fuse until the power wire has been securely connected to the amplifier.

4) Run signal cables and remoteturn-onwire from the source unit to the final amplifier mounting location.

5) Run speaker cables from the speaker systems to the amplifier mounting location.

6) Find a good, solid metal grounding point close to the amplifier and connect the negative power wire to it using

appropriate hardware (use of the JL Audio ECS master ground lug, XB-MGLUis recommended). Use 8 or 4 AWG wire, no longer than 36 inches (90 cm) from the amplifier to the ground connection point. In some vehicles, it may be necessary

to upgrade the battery ground wire. (See page 5 for important notice).

7) Securely mount the amplifier.

8) Connect the positive and negative power wires to the amplifier. A fuse near

the amplifier is not necessary if the XD400/4 is the only device being run from the fused main power wire. If the fused main power wire is shared by the XD400/4 and other amplifiers or devices, fuse each amplifier/device

within 12 inches (30 cm) of wire length, via a fused distribution block or multiple individual fuse blocks/on-boardfuses.

9) Connect the remoteturn-onwire

to the amplifier.

10)Connect the input cables to the amplifier.

11)Connect the speaker cables to the amplifier.

12)Carefully review the amplifier’s control settings to make sure that they are set according to the needs of the system.

13)Install the power wire fuse (40A for a single XD400/4) and reconnect the negative battery post terminal. Install the fuse (40A) near the amplifier (if applicable).

14)Turn on the source unit at a low level to double-checkthat the amplifier is

configured correctly. Resist the temptation to crank it up until you have verified the control settings.

15) Make necessary adjustments to the input sensitivity controls to obtain the right overall output and the desired balance in the system. See Appendix A (page 14) for the recommended input sensitivity setting method.

16)Enjoy the fruits of your labor with your favorite music.

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Power Connections

Before installing the amplifier, disconnect the negative (ground) wire from the vehicle’s battery. This will prevent accidental damage to the system, the vehicle and your body during installation.

The XD400/4’s “+12 VDC” and “Ground” connections are designed to accept8-4AWG power wire.8 AWG is the minimum required wire size for this amplifier.

If you are installing the XD400/4 with other amplifiers and wish to use a single main power wire, use 4 AWG, 2 AWG or 1/0 AWG main power wire (depending on the overall current demands of all the amplifiers in the system). This large power wire should terminate into a fused distribution block mounted as close to the amplifiers as possible (within 12 inches / 30cm of wire length). The fused output of the distribution block will connect to the XD400/4 with 4 AWG power wire. JL Audio ECS

fused distribution blocks are recommended (XD-FDBU-2andXD-FDBU-4)

Note: Smaller AWG numbers mean bigger wire andvice-versa(1/0 AWG is the largest, 2 AWG is smaller, then 4 AWG, then 8 AWG, etc.).

To connect the power wires to the amplifier, first back out the set screw on the top of the terminal block, using the supplied 2.5 mm hex wrench. Strip 1/2 inch (12 mm) of insulation from the end of each wire and insert the bare wire into the terminal block, seating it firmly so that no bare wire is exposed. While holding the wire in place, tighten the set screw firmly, taking care not to strip the head of the screw.

The ground connection should be made using 8 or 4 AWG wire and should be kept as short as possible, while accessing a solid piece of sheet metal in the vehicle. The surface of the sheet metal should be sanded at the contact point to create a clean, metal- to-metalconnection between the chassis and the termination of the ground wire. For optimal grounding, we recommend the use of a JL Audio ECS master ground lug(XB-MGLU).Alternatively, a sheet metal screw or bolt can be used with a star washer.

Any wires run through metal barriers (such as firewalls), must be protected with a high quality rubber grommet to prevent damage to the insulation of the wire. Failure to do so may result in a dangerous short circuit.

Many vehicles employ small (10 AWG - 6 AWG) wire to ground the battery to the

vehicle chassis and to connect the alternator's positive connection to the battery. To prevent voltage drops, these wires should  be upgraded to 4 AWG when installing amplifier systems with main fuse ratings above 60A.

Fuse Requirements

It is absolutely vital that the main power wire(s) to the amplifier(s) in the system be fused within 18 inches (45 cm) of the positive battery post connection. The fuse value at each power wire should be high enough for all of the equipment being run from that power wire. If only the XD400/4 is being run from that power wire, we recommend a 40A fuse be used.

If fusing the amplifier near its power connections (when more than one amp is being run from the main power wire), use a 40A fuse.

MAXI™ plastic-bodyfuses are recommended.




The XD400/4 uses a conventional +12V remote turn-onlead, typically controlled by the source unit's remoteturn-onoutput. The amplifier will turn on when +12V is present at its “Remote” input and turn off when +12V is switched off. If a source unit does not have a dedicated remoteturn-onoutput, the amplifier’sturn-onlead can be connected to +12V via a switch that derives power from anignition-switchedcircuit.

The XD400/4’s “Remoteturn-onconnector is designed to accept 18 AWG – 12 AWG wire. To connect the remoteturn-onwire to the amplifier, first back out the set screw on the top of the terminal block, using the supplied 2.5mm hex wrench. Strip 1/2 inch (12mm) of wire and insert the bare wire into the terminal block, seating it firmly so that no bare wire is exposed. While holding the wire in the terminal, tighten the set screw firmly, taking care not to strip the head of the screw and making sure that the wire (not the insulation) is firmly gripped by the set screw.

Input Section

The XD400/4’s input section allows you to send signals to the amplifier section through the use of two or four differential-balancedinputs. Input connections are via up to two pairs of

traditional RCA-typejacks.

If you wish to send four discrete channels into the XD400/4, simply use all four inputs and set the “Input Mode” switch in the “4 Ch.” position.

If you wish to use only two channels of input to deliver signal to all four amplifier channels, set the “Input Mode” switch to “2 Ch.” and use only the inputs to channels 1 & 2. In this mode, Channel 3 will operate with the Channel 1 signal and Channel 4 will operate with the Channel 2 signal.

Input Voltage Range:

The XD400/4’s input sections are designed to accept signal voltages from 100mV – 4V. This will accommodate all preamp level signals and many speaker level signals.

To use speaker-levelsources, simply splice the speaker output wires of the source unit onto a pair of RCA plugs for each input pair. (or use JL Audio partXD-CLRAIC2-SW)No “line output converter” is needed in most cases.

If you find that the output cannot be reduced sufficiently with a direct speaker level signal applied to the amplifier, you may use a “line output converter” to reduce the signal level.

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Input Sensitivity Controls

The controls labeled “Input Sens.” located in each channel section can be used to match the source unit’s output voltage to the input stage of each pair of amplifier channels for maximum clean output. Rotating the control clockwise will result in higher sensitivity (louder for a given input voltage). Rotating the control counterclockwise will result in lower sensitivity (quieter for a given input voltage.)

To properly set the amplifier for maximum clean output, please refer to Appendix A (page 14) in this manual. After using this procedure, you can then adjust any or all “Input Sens.” levels downward if this is required to achieve the desired system balance.

Do not increase any “Input Sens.” setting for any channel(s) of any amplifier in the system beyond the maximum level established during the procedure outlined in Appendix A (page 14). Doing so will result in audible distortion and possible speaker damage.



Filter Controls

Most speakers are not designed to reproduce the full range of frequencies audible by the human ear. For this reason, most speaker systems are comprised of multiple speakers, each dedicated to reproducing a specific frequency range. Filters are used to select which frequency range is sent to each section of a speaker system. The division of frequency ranges to different speakers can be done with passive filters (coils and/or capacitors between the amplifier outputs and the speakers), which are acceptable and commonly used

for filtering between mid-rangespeakers and tweeters. Filtering between subwoofer systems and satellite speaker systems is best done with active filters, which cut off frequency content at the input to the amplifier. Active filters are more stable than passive filters and do not introduce extraneous resistance, which can degrade subwoofer performance.

The active filter built into each channel section of the XD400/4 can be used to eliminate potentially harmful and/or undesired frequencies from making their way through the amplifier sections to the speaker(s). This serves to improve tonal balance and to avoid distortion and possible speaker failure. Correct use of these filters can substantially increase the longevity and fidelity of your audio system.

1)“Filter Mode” Control: The XD400/4 employs a 12dB per octave filter for each pair of channels (one filter for channels 1&2, another filter for channels 3&4 and a third filter for channels 5&6). Each of these filters can be configured independently into one of two filter

types or defeated completely by way of the three-position“Filter Mode” switches:

“Off”: Defeats the filter completely, allowing the full range of frequencies present at the inputs to feed the amplifier. This is useful for systems utilizing outboard active crossovers or requiringfull-rangereproduction from one or more of the XD400/4’s channel pairs.

“LP” (Low-Pass): Configures the filter to attenuate frequencies above the selected filter frequency at a rate of 12dB per octave. This is useful for connection of subwoofer(s) to one or more of the XD400/4’s channel pairs in abi-amplifiedsystem.

“HP” (High-Pass): Configures the filter to attenuate frequencies below the selected filter frequency at a rate of 12dB per octave. This is useful for connection of component speakers to one or more of the XD400/4’s channel pairs in abi-amplifiedsystem.

2)“Filter Freq. (Hz)” The filter frequency markings surrounding this rotary control are for reference purposes and are generally accurate to within 1/3 octave or better. If you would like to select the filter cutoff frequency with a higher level of precision, consult the chart in Appendix B (page 15).

Tuning Hint:  If you are using the XD400/4 to drive a subwoofer system (“LP mode), a

component satellite speaker system (“HP mode) or both, 80 Hz is a good baseline “Filter Freq. (Hz)” setting. After properly adjusting the “Input Sens.”, as outlined in Appendix A (page 14), you can fine tune the “Filter Freq. (Hz)” control to achieve the desired system frequency response.

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Remote Level control (Optional)

With the addition of the optional Remote Level Control (HD-RLC),you can control the volume of one, or both channel pairs of the XD400/4 from the front of the vehicle. This is useful for subwoofer level control, rear channel level control,center-channellevel control or even as a master volume control for the system.

The HD-RLCconnects to the jack labeled “Remote Level Control” on the Connection Panel of the amplifier using a standard telephone cable (supplied with theHD-RLC).If desired, multiple XD (and HD) amplifiers can be controlled from a singleHD-RLCcontroller using a simple phone line “splitter” and multiple phone cables.

When connected to the amplifier, the HD-RLCoperates as follows. At full counterclockwise rotation, the audio will mute completely. At full clockwise rotation the level will be the same as if theHD-RLCwas not connected at all. In other words, it operates strictly as a levelattenuator.

“Remote Level Mode” Switch: This switch allows you to assign the operation of the HD-RLC to one, or both pairs of channels. In the “All”position, the HD-RLC knob will affect all three channel pairs equally. In the “3&4”position, only the level of channels 3 and 4 will be affected by the HD-RLC knob (Channels 1 & 2 will not).


The XD400/4 incorporates a pass-throughpreamp output section, so that additional amplifiers can be easily added to the system. Thispass-throughpre-ampoutput can be configured two different ways using the switch labeled “Preouts From”.

1)“1&2”: The preamp output delivers the same signal that is connected to the CH 1&2 Inputs. This mode is useful for feeding a subwoofer amplifier when the XD400/4 is being used to drive front and rear speaker systems. In this mode, the preamp output signal will depend only on the input signal level of CH 1&2, allowing Channels 3&4 to be faded without affecting the subwoofer level. If CH 1&2 is faded in this mode, the signal level of the preamp output will change accordingly.

2)“Sum”: When the XD400/4 is being used to drive front and rear speaker systems, this preamp output mode will deliver a summed

front/rear stereo signal to a subwoofer amplifier, while permitting fading of the front and

rear speaker systems from the source unit. This method prevents a loss of signal to the subwoofer amplifier when the system is faded to the front or the rear by the head unit.

Note: Any signal delay between the front and rear channels can result in a cancellation of signals within certain frequency ranges when using the “Sum” position. If you experience a loss of bass output in the “Sum” position, compared to the “1&2” position, you are likely dealing with a delayed signal in either the front or rear outputs of the source unit. If the front to rear delay is desirable for other reasons or if it cannot be defeated at the source unit, we recommend that you use the “1&2” position.

Note: In either mode, the preamp output signal is not affected by any crossover filter selected (if the input signal isfull-range,the preamp output will befull-range).




The XD400/4’s speaker outputs are designed to accept 16 AWG - 8 AWG wire. To connect the speaker wires to the amplifier, first back out the set screws on the top of the terminal block, using the supplied 2.5 mm hex wrench. Strip 1/2 inch (12 mm) of insulation from the end of each wire and insert the bare wire into the terminal block, seating it firmly so that no bare wire is exposed. While holding the wire in place, tighten the set screw firmly, taking care not to strip the head of the screw.

Each pair of the XD400/4’s channels are designed to deliver power into speaker loads equal to or greater than 2 ohms when using a “stereo” configuration and speaker loads equal to or greater than 4 ohms when using a “bridged” configuration.

Speaker loads below 2 ohms nominal per channel (or 4 ohms bridged) are not recommended and may cause the amplifier to initiate a protection mode which reduces power output.

Bridging Considerations

Bridging is the practice of combining the output of two amplifier channels to drive a single load. When bridged, each channel produces signals of equal magnitude, but opposite polarity. The combined output of the two channels provides twice the output voltage available from a single channel. The XD400/4 has been designed for bridging of its channel pairs without the need for input inversion adaptors.

To bridge a pair of channels, use the “Left +” and “Right speaker connectors only (the

Left and “Right +” remain unused). When bridged, each channel will deliver optimum power into a 4 ohm load.

When a pair of channels are bridged, they will deliver 200W x 1 into a 4 ohm load or 150W x 1 into an 8 ohm load. Operating a pair of bridged channels into a load lower than 4 ohms is not recommended.

Because a bridged pair of channels requires that both channels receive input, you need to connect both left and right inputs to the source unit. Connection of only one input will result in reduced power output, increased distortion and can cause the amplifier to overheat.

Do not do this!

When a pair of the XD400/4’s channels are operating in bridged mode, the output will be in mono (only one channel). This mono channel can contain right channel only information, left channel only information or the sum of

the information from both the right and left channels. In order to achieve one of these options, configure the inputs to that pair of channels in one of these two ways:

1)Left Channel Only or Right Channel Only Information: If you wish to send a left-only or right-only signal to a pair of the XD400/4’s channels, use a “Y-Adaptor” to split the single channel signal into both left and right RCA inputs. This option is useful when using a pair of the XD400/4’s channels to drive left channel speakers only and the other pair of the XD400/4’s channels to drive right channel speakers only.

2)Left + Right Channel Information: When bridged and fed by a stereo input, a pair of the XD400/4’s channels will automatically combine the left and right channels into a summed mono (left + right) channel. This option is useful when using a pair of the XD400/4’s channels to drive a subwoofer system or a summed mono center channel.

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