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JL Audio XD400/4

4-channel car amplifier — 75 watts RMS x 4 (New Stock)

21 Reviews | 1 question - 1 answer

Item # 136XD4004

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JL Audio XD400/4v2




Our take on the JL Audio XD400/4

Each JL Audio XD amp packs a wallop far beyond what you'd expect from something so small. This super-compact amp plays your music with true fidelity and impressive impact, without straining your car's electrical system. A cast alloy heatsink and an advanced cooling system keep these amps at optimal temperature, eliminating thermal shut-downs so your music keeps going strong without interruption.

Each JL Audio XD amp packs a wallop far beyond what you'd expect from something so small. This super-compact amp plays your music with true fidelity and impressive impact, without straining your car's electrical system. A cast alloy heatsink and an advanced cooling system keep these amps at optimal temperature, eliminating thermal shut-downs so your music keeps going strong without interruption.

The JL Audio XD400/4 4-channel amp can deliver 75 watts RMS per channel to 2 pairs of speakers, or it can drive a full set of separate tweeters and woofers with its four channels. You can even bridge the XD400/4 into 2-channel mode to power a couple of subs with 200 watts each. High- and low-pass filters give you intimate control over the character of your sound.

"Differential-balanced" inputs keep the signals clear of outside noise, and allow you to connect this amp to just about any in-dash stereo, even a factory radio with no preamp outputs. An optional wired remote lets you tweak the level from your front seat.

Product Highlights:

  • 4-channel car amplifier
  • 75 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
  • 200 watts RMS x 2 bridged at 4 ohms (4-ohm stable bridged)
  • variable low- and high-pass filters (50-500 Hz, 12 dB/octave)
  • optional wired remote for level control
  • Class D amplifier design with NextD™ switching amp technology
  • differential-balanced inputs eliminate noise coming from your vehicle's electrical system
  • Advanced Rollback Protection System prevents thermal shut-down
  • speaker- and preamp-level inputs (speaker-level input requires an optional adapter)
  • preamp outputs
  • 4-gauge power and ground leads and a 40-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 40-amp in-line fuse between the distribution block and the amplifier is recommended
  • 8-1/2"W x 2"H x 7-3/8"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

Swampy out a pair of crappy amps for a pair of these and it like a whole new world. Fantastic sound and with bass volume knob it is perfect. Incredible sound.

Mike, Valley stream , ny

What's in the Box:

  • 4-Channel class-D amplifier
  • Hex-key
  • JL Audio emblem
  • Owner's Manual

JL Audio XD400/4 Reviews

Average Customer Review(s):

(21 Reviews)

Good, but not for higher end speakers

CW from United States on 12/4/2014

I installed the JL XD 400/4 to bi-amp a front stage set of focal poly-kevlar components with active crossovers set in the headunit. This amp is great for its versatility, low current draw, and power for its size. I even used the selectable pass-thru to feed another set of mids in the rear. But if you have speakers/tweeters capable of producing really detailed sparkling high frequencies, this amp is not the best choice. Power is clean and can play as loud as u want it to. But this is not for anyone building a system focussed on sound quality. Replaced this amp with a used focal solid 4 and heard the difference in my music immediately.

Pros: Can fit anywhere Great power for its size

Cons: Sound quality not as good as a decent class A/B amp.

Not for me

Michael from PA on 5/29/2014

Crutchfield Customer Review (What's this?)

This amp sounded terrific at low to moderate levels. When playing it loud though, it was a dif story. I set the gain properly, but u can clearly hear distortion where with my previous 75x4 there was none at the same volume levels. I exchanged it for the JL Audio Slash 300 and couldn't be happier. No distortion whatsoever!

Pros: Great sound at low and moderate levels. Very small footprint. Uses very little power.

Cons: Struggles with distortion when played at high volumes.

Disappointing performance

DaytonAve from Ohio on 10/8/2013

Crutchfield Customer Review (What's this?)

The XD400/4 is my fourth 4-channel amp to grace my cars throughout the years. I am running a Pioneer DVD head unit, through the JL amp into Focal Access components in an Audi S4. After ~5 weeks of burn-in, tweaking, tuning, etc, I still could not achieve a sound with which I was satisfied. My reference material (Dire Straits/Brothers in Arms SACD, Nils Lofgren/Acoustic Live, Elton John/(various SACDs) lacks the dynamic punch I've had with every other system. The sound quality for low-level listening is quite good, specifically in it's low frequency control. However, dynamic recordings are uninspiring with all of them feeling "brickwalled." By replacing the factory Bose system with an aftermarket amp, I did so with the purpose of being able to appreciate the transients and dynamics inherent in music. Another downside was the listener fatigue noticed during longer drives. I have had profound listener fatigue with factory systems in many vehicles, but never with my aftermarket systems. I purchased the amp through Crutchfield because they have the most generous return policy in the business. It was sent back after 6 weeks and replaced with an Alpine PDX, which has been fantastic up to this point

Pros: Form factor/size, solid construction, tight bass control

Cons: Lacks dynamics, disappointing upper frequencies, listener fatigue on long trips


Mike from Valley stream , ny on 8/13/2013

Swampy out a pair of crappy amps for a pair of these and it like a whole new world. Fantastic sound and with bass volume knob it is perfect. Incredible sound.

Pros: Size, volume knob

Cons: None

This amp fits in my hand

Charles from CHICAGO ill on 3/16/2013

OK, when i first saw this amp on the website i was looking for a 4 Channel that would not take up the whole trunk. Once I installed it & did my fine tuning, i was truly impressed,and it's so small that friends ask me WHERE IS THE AMP!! I have it running a 6 inch in the doors & 6 by 9. Upgrade coming soon. Thanks Crutchfield.

Pros: Small footprint,easy to set up,and the power nice and clean. Not amp pop went comes on are powers off.

Cons: ........ NONE.


Jerry T from Phoenix, AZ. on 1/31/2013

Crutchfield Customer Review (What's this?)

I have a 2001 Mustang convertible. I had to find an amp theat would fit behind the rear seat. This was that amp... I completely tore out the stock sound system (Mach 460). I paired this amp with a Pioneer AVH-P2400BT. For speakers; JL Audio C5 570's in the front and C3 600's in the rear. I still cannot believe how awesome my system sounds! Running 70 mph down the highway with the top down is no longer an issue! I get loud, powerful, clear sound and there is volume to spare. I have been working with Crutchfield for more than 15 years and all I can say is they are second to none. They have saved me literally thousands of dollars! A huge THANK YOU to Hogan (xt. 3210) and all the staff at Crutchfield, you have a customer for life!

Pros: SIZE, Easy to Instal, SIZE, very powerful unit

Cons: None so far

JL Audio XD400/4

Mykhaylo from Cleveland, OH on 1/27/2013

Crutchfield Customer Review (What's this?)

Pretty powerful clear very good channel separation



Choked on a bone.

Rroppmd from Chicago on 1/18/2013

I really liked my setup with this amplifier but after 2 years it started to give me trouble. It was suggested by Crutchfield to replace the speaker but that didn't fix the problem and the installer told me to look into a new amplifier. I didn't think that this was a trial and error fix. Now my right rear subwoofer and speaker cut out when I start up the car.

Pros: It has as nice sleek design that looks neat and tidy. There are many features that are adjustable. The wiring setup makes changing connections easily accessible.

Cons: The amp really needs to have a ventilation/heat exchanger setup.

Great things come in small packages

TomRiv from Boston, MA on 8/1/2012

Crutchfield Customer Review (What's this?)

First off this is the first time I've ever installed an amplifier, and while the thought of drilling holes and running all those wires was intimidating I'm really glad I did it. It was easily installed under the passenger seat of my Subaru Forester with lots of room to spare. The end result is worth it, my music is noise free and this can really push a set of high end speakers to the limits... OMG can this thing get loud! I paired this with just a set of Polk Audio MM6501 component speakers (2.7 Ohm rated at 120W RMS) to start off, and even with the gains only set halfway the volume can get unbearable. However at "reasonable' volume levels the music is clean and clear, so much so I no longer mind sitting in traffic on the MassPike! =) Next up I'll be hooking up a Polk Audio MM840 subwoofer to the rear channels, can't wait to see how it sounds when I'm all done!

Pros: Zero noise, minuscule footprint compared to other amps with similar wattage, no heat buildup at all.


Big sound small package

hifonix from Greenville, NC on 7/17/2012

Crutchfield Customer Review (What's this?)

I have had this amp installed for over 1 year now. Let me say that when they first came in, xd400/4 and xd 600/1 I was shocked by the size. I replaced old school hifonics XI series amps with these little JL audio's. My first thought OH GOD WHAT HAVE I DONE. Well this proved to be the wrong thought, these little amps are power houses and clean. I would relate them to the old PPI art series for clarity. Going from old school large amps to these small amps has given me my trunk space back, and cleaned up the sound amazingly.Had this amp running a pair of Polk MOMO 6.5 inch fronts and Polk MM 6.5 inch rear componets. Did not have enough power to keep up with subs, solution added a 2 channel XD 200/2 for rear, and bridged 4 channel to front. JL has a winner here scoop them up before they realize and raise the price!!!!!

Pros: Small, Clean, and Powerful.

Cons: Not really a CON I knew what I was buying. Went from a hifonics XI europa (125x4@ 4 ohms) Wasnt enough power alone for my two componet sets.Wish it came in a bigger size say 125x4 @ 4ohms. After 1 year of use no issues.

Jl audio XD 400/4

Kaytay from Mason, ohio on 4/18/2012

Crutchfield Customer Review (What's this?)

I will make this short and sweet, this amp is extremely clean with plenty of juice to power front and rear jl components. I needed space and was hopeful this would be the answer, and it's like I never switched from my jl 300/4. Great amp !

Pros: Good power, clean , tiny footprint

Cons: Only con is my 300/4 had better crossover

JL XD 400 amp

Frankie L. from New York, ny on 1/30/2012

Crutchfield Customer Review (What's this?)

What power in a small package. This amp can fit anywhere.

Pros: Great power in a little package.

Cons: None

Nice and compact

t s from Dallas on 12/27/2011

Crutchfield Customer Review (What's this?)

I was looking for an amp to replace the stock amp on my 2011 Camaro, and this was one of the few that would fit in the stock location. Sounds great, very heavy for being so compact. Hopefully it is typical JL quality and will last for years to come.

Pros: Very compact, sounds nice

Cons: a little bit pricey for such a small amp

JL xd400/4

Ryan M from Wisconsin on 10/4/2011

The JL Audio xd400/4 is a solid amplifier, ultra small footprint compaired to the slash series. Running in 4CH mode,Powering JL C5-525 components up front and C2-690tx in the rear deck with authority and clarity. Will offer plenty of power for any 4CH speaker setup, at moderate to loud volume the amp remains cool/warm to the touch, nothing but the highest quality when choosing JL Audio!



incredible amp

chuck H. from Lake Mary,FL on 7/18/2011

Crutchfield Customer Review (What's this?)

I purchased this amp along with a JL 8" subwoofer.The amp will surprise you,alot of power in a small package.Handles it very well powering a sub-woofer and polk component speakers,7 speakers in all and plenty of power to spare.would reccomend this amp to anybody.I'm deffinately a JL Audio fan now.



Great small amp with lots of power

kontai69 from Vacaville, CA on 4/17/2011

Crutchfield Customer Review (What's this?)

I bought this amp to power a pair of Polk 6.5" component speakers and a JL Audio 8" sub in my 2011 Honda CR-V. The amp is fed with the output from an Audiocontrol 2-channel line output converter. The amp is very small (slightly wider than a dollar bill) and fits underneath the driver's seat with plenty of room to spare. The amp is extremely well built and impeccably finished. I like how the amp controls are hidden underneath a cover and that the wire connections are all on one side. In my application, all this makes for a VERY clean looking install with no visible wires. The amp also has alot of controls to make it very flexible in terms of connectivity. The low and high pass filters have defined indentations to allow for precise setting of cutoff frequencies. The amp seems to power the speakers/sub effortlessly with no audible noise or distortion. I bridged two of the channels to power the 8" sub. It is quite pricey, but well worth the cost. TMK, it is the smallest amp on the market that puts out this much power. Overall, a very great purchase!



A tiny powerhouse!

SpencerW from Houston, TX on 12/13/2010

I bought my JL Audio XD400 because of its small size. I have it installed under the passenger seat of a 2010 Smart Passion coupe. My head unit is a Kenwood DNX9960. Although the JL amp is tiny, it is driving the crap out of a JBL GTO-804 subwoofer and a pair of Focal 165 VR components. The sound quality is incredible, and it never gets hot. It seems like the more you push it, the tighter and cleaner the sound becomes. If you have severe space constraints, or you just want a very clean amp to drive a few speakers, this is your best bet!



Great amp

Chris from Schuylkill Haven, PA on 11/27/2010

Crutchfield Customer Review (What's this?)

This tiny little amp is great. Easy to hook up and goes just about anywhere because of it's small size. Speakers sound great and have no power interference noise at all. Hard to believe that much power comes from such a small amp, but it does. You won't be disappointed with this amp. Good job JL Audio.



JL Audio XD400/4

Sing from pensacola, FL on 8/3/2010

Excellent quality amp. zero noise. easy installation. Best amp I've ever owned.



small amp big sound

chipss from lafayette la on 7/28/2010

Size: One of this amps best futures, if you have an install with limited space, this amp is a no brainier, I have it installed sideways under the middle seat of an f150, with room to spare, but it would fit in the glove box, in the dash, under either seat. Many options due its size, Controls: Amp has the usual stuff, you can read about on this site, some notes of mine are that the remote level control can be set up to fade to the rears if running rear speakers. I am running component speakers active, 2 ways, so I can blend mids and tweeters with the knob, very cool for fine tuning. One weakness on this amp are the crossovers, 80 to 500 cycles is very limiting, I personally do not use them, its just a heads up. All wire hook ups are on one side, very cool and again makes for a clean install. I spoke with JL techs today and the amp will run bridged two sets of 4 ohm speakers at 200 WPC. Very impressive, and allows for future upgrades. Sound: I hotly debated subject is weather amps have sonic signatures, I will not go there, I will say, its hard to believe this little guy puts out solid clean power in such a little package, but it does, not even a hint of hiss, My subjective review is that this amp sounds good, real good, and I am so impressed with it my pdx 600/1 will be replaced with an XD as well. I give this amp a solid and honest 4 rating.



Excellent amplifier

Scott from San Diego, CA on 5/14/2010

Crutchfield Customer Review (What's this?)

I purchased this item to replace a Polk Audio PA200.4 car amplifier that I originally installed during my stereo upgrade. The Polk amp was creating a noticeable hiss in all of the connected speakers that was independent of volume and very annoying. The noise was present even when only the amp was connected to the speakers (with no inputs feeding into the amp), so the amp was definitely the culprit. I returned the Polk amp and purchased this amp instead. Although this amp is obviously nicer (and more expensive), the difference is major. This amp is around half the size and more powerful. Plus it produces an extremely clean signal (the user manual credits this to differentially balanced inputs, though I can only tell you that whatever they are doing works). I highly recommend this amp over cheaper amps such as the Polk Audio PA200.4, as you will notice a major difference. *Note that I have purchased a more expensive Polk amp in the past and have been extremely satisfied with its clean and powerful sound. I think in general it is always wise to stay away from the bottom-line amps, no matter what brand you choose.




Hands-on research

Product Research



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 system configuration.

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 muted.
  • 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 speaker wiring.
  • 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 screws.

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.


Power/Ground/Turn-On Terminals: The amplifier features set-screw terminals for the power, ground, and remote turn-on connections.

  • 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 will accept 18 to 8 AWG wire. The same 2.5mm hex-wrench is supplied for making connection.

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.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Q & A

Customer Q&A

1 question already asked

If you purchased the product from Crutchfield, feel free to contact our Tech Support team. They can walk you through the settings on the product and see if there may be a fix. Our toll-free Tech Support number is printed on your invoice, and is also available under the "My Orders" tab in the "My Account" section of our website. If you did not purchase the unit from Crutchfield, then you may want to contact the manufacturer. You can also post your question in our forums: Or try our online support center: [ Krissy  Mar 30, 2014 ]  Staff