In-Depth Review: JL Audio XD400/4 4-Channel Amp

RB XD400/4 JL Audio 4 Channel Amp Review

Are you in the market for a new amplifier? Perhaps your old one just blew out, or you’re looking to upgrade to a better option? If you want a serious player in the car stereo space, you might want to try the RB XD400/4 JL Audio 4 Channel AMP with 400 Component Speakers Tweeter Amplifier.

Who Should Buy This Product?

Anyone who wants rugged build quality, minimal distortion, and peak power sound. People who want a consistent power output while keeping things lean and mean. If you want a crisp and clear sound on an amp that won’t overheat, the JL Audio 4 Channel is the right choice for you. Those who want an efficient sound from a heavy hitter in a tiny package.

If you like a small package that puts out a big sound, you’ll love this amp. It’s compact, and you can put it pretty much anywhere as long as it’s got airflow. It won’t make for clutter even in smaller cars. If you’re someone who enjoys full bandwidth Class D that displays clear highs and lows you can control from your driver’s seat, this is for you.

What You Should Know

This product has a Watts RMS rating at 75 watts per channel at 4 ohms, 150 watts at 8ohms, and 100 watts at 2 ohms. This amp is not cheap. However, it’s top-quality, and the sound you get from this little amp is well worth the money.


The JL Audio 4 Channel Amplifier comes with advanced rollback protection. This feature makes sure the thermal condition is at the right temperature , which prevents the amp from shutting down.

The NexD Switching Technology brings forth amazing sound quality that also has top of the line efficiency while maintaining its big power. All of this is done with an extremely compact amp design.

It has an 80% NexD ultra-fast class D power switching supply enabled by a 12dB/octave Butterworth and can be configured for high or low pass. Rated power is 14.4V Stereo. The dimensions are 8.52in.-L x 7.09in.-W x 2.05in.-H

It comes coated in black aluminum heatsink and a brushed aluminum final piece badge and panel. There’s also a socket for an optional HD-RLC knob for remote control. Combination monoblock building a 1000 watt amp system that can power four satellites and a subwoofer.

Differential balanced input will eliminate any noise from your car’s electrical system.

Preamp inputs and outputs. Two-year warranty.

First Impression

When you first see the size of the JL Audio 4 Channel Amp, you don’t think it’s going to provide much of a kick, but it does. The sound will blow you away with both power and clarity. You’ll feel the difference between this and most other 4 channel amps, and although it’s more expensive than most other 4 channels, the quality is worth the price.


This amp packs a wallop of power, and it’s virtually indestructible. You won’t blow it even if you short the leads. You’ll hear great detail in the sound at lower levels and be able to blow the doors off when you want to with this amp.

The clean sound of this amp won’t give you any static during song pauses or break in between. You’ll get a much louder and clearer sound than most other brands on the market. It’s definitely worth the price.


It must be mounted in an open place to provide airflow. It’s not cheap. (About $600)


If you purchase the RB XD400/4 JL Audio 4 Channel Amp, you’ll definitely be happy. By all accounts, this little amp doesn’t disappoint. You’ll immediately see the difference when you upgrade from another system.

If you’ve wanted to buy a new amplifier for your car, you don’t need to look much further than this amp. If you’ve got $600 to spend, then you’re in luck. The JL Audio 4 Channel will make for an amazing car audio and driving experience. The big sound you will get from such a small piece of equipment is mind-blowing. Not to mention it’s crisp as can be.


Have more questions about the amp and whether or not it’s for you? Check these out.

Q: What are the dimensions?

A: The dimensions are 8.52in.-L x 7.09in.-W x 2.05in.-H.

Q: Can this amp power 2 JL Audio cr 650-csi speakers?

A: It’s more than enough, it’s 75 watts per channel and yours are 25-85.

Q: Can it be directly connected to an oem radio?

A: Yes, if the oem has RCA outlets.

Q: Should I get a focal amp, or is the JL better?

A: The JL has a better track record with no heating or distortion.

Q: Will it work with JL c5-525 component speakers and c2-525x coaxial speakers?

A: Absolutely. It’s the perfect fit for that.

Q: Is there a popping sound or a great deal of static when turning the vehicle off?

A: Not at all. If you do experience this, then the device isn’t connected properly.

Q: Will it be able to play my dual 8″ jls and speakers?

A: It’s a four-channel amp, best for two loudspeakers and your subwoofers.

Final Thoughts

The RD X400/4 JL Audio 4 Channel Amplifier is awesome. There aren’t many bad things to say about it except for maybe the price. However, when you compare the quality of the product, the crispness of the sound, the power it kicks out, and the overall sharpness, you pretty much can’t go wrong here.

I’d say this is definitely a 4.9 out of 5 stars. The only drawbacks are the fact that you should mount it in the open for airflow and the price is higher than most 4 Channel amps out there. That being said, this is a high-quality product and well worth the money you’ll spend on it. You won’t be disappointed.

So it’s time to take a look at our guide to the best 4 channel amps and make your decision. The difference this amp will make in your car is amazing. You’re sure to have a smile on your face when you pump up the volume with this little beast.

Brett Gordon

The engine behind editing at DigMyRide and the brains behind its build. During the day, Brett is a thirty-something dude from SoCal climbing the corporate ladder, but by night, he spends his time contributing to the online world of automotive tech & trends.