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Kicker 40KX400.4

4-channel car amplifier — 50 watts RMS x 4

Item #: 2064KX4K4

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5 Reviews | 1 question - 2 answers

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Delivers dependable power with style

Kicker's KX400.4 4-channel amplifier will power your front and rear speakers with 50 watts RMS each, bringing brilliance and clarity to your sound. This reliable and compact KX Series rocker remains cool even when pushed hard, thanks to its high-mass heatsink, high-tech internal components, and efficient full-range Class-D amp technology. Building a system and wondering what to buy first? You could start with this amp in 2-channel mode to drive a couple subs with up to 200 watts each, then switch the amp over to power all your speakers when you get a bigger sub amp.

Connects to virtually any system

Kicker employs their Fail-Safe Integration Technology (FIT™) to reject noise and stop any interference generated by your car's electronics, so you'll enjoy your music clean and pure. Speaker-level inputs make it possible to hook this amp up to almost any stereo, even a factory system. Kicker even thought to build in a 3-second turn-on delay, eliminating any annoying and potentially damaging turn-on pops.

Versatile controls behind the folding door

You can tune for almost any kind ofspeaker, as the steeply-sloped high- and low-pass filters offer a wide range of adjustment. The filter section for the rear channels can be set up for bandpass operation – where both the high- and low-pass filters are engaged to allow only the frequencies between them to play – for optimizing the signal to midrange drivers or other component speakers. The front and rear channels offer separate bass boosts, giving you more flexibility for adding some kick to your music.

Kicker KX400.4 control panel

                                                                          KX400.4 control panel

Product Highlights:

  • 4-channel car amplifier
  • 50 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 in bridged mode)
  • CEA-2006 compliant
Front channels:
  • variable high- and low-pass filters (10-5000 Hz, 24 dB/octave)
  • variable bass boost (0-18 dB at 40 Hz)
Rear channels:
  • variable high-pass filter (10-500 Hz, 24 dB/octave)
  • variable low-pass filter (10-5000 Hz, 24 dB/octave)
  • variable bandpass filter (10-5000 Hz, 24 dB/octave)
  • variable bass boost (0-18 dB at 40 Hz)
More info:
  • front-mounted controls protected behind fold-down door with magnetic latches
  • Class D amp technology
  • Fail-Safe Integration Technology eliminates noise from your vehicle's electrical system
  • preamp and speaker-level inputs (speaker wire to RCA adapter required for speaker-level input)
  • preamp outputs
  • 4-gauge power and ground leads and an 80-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amplifiers in a system, an additional 80-amp in-line fuse between the distribution block and this amplifier is recommended
  • 11-3/16"W x 2-3/16"H x 8-3/4"D
  • warranty: 2 years (extends to 3 years when purchased with either a Kicker single amp wiring kit or a Kicker multi-amp kit)
  • Our 60-day money-back guarantee

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

Kicker 40KX400.4 Reviews

Average Customer Review:

5 Reviews


Written by: Amp from Lafayette on December 9, 2015

Crutchfield Customer Review (What's this?)

Great product

Pros: None

Cons: None

Kicker 400.4

Written by: Mckulos from California on May 26, 2015

Crutchfield Customer Review (What's this?)

Good amp.. Easy hook up and adjustment.

Pros: Everything is good about it. Would buy another for a future car system


Great Choice for added sound detail

Written by: D.Banks from Mississippi on December 5, 2014

Crutchfield Customer Review (What's this?)

This is simply a great choice for that extra all around sound with detail. This is a very diverse amplifier that has the power to take you to the next level of audio in your vehicle. The variable adjustments are great; but what makes them even greater is that they can be concealed for a super clean look on install. This is a complementing amplifier to the KX1200.1 if you are looking for great 4Ohm or 2Ohm loads from your subs.

Pros: Hide away adjustments are fantastic!

Cons: Should have purchased sooner.

proof of power

Written by: j.wisdom from beaumont,tx on April 3, 2014

Crutchfield Customer Review (What's this?)

Lots of power

Pros: All digital , runs cools to the touch

Cons: Needs a lil more high end.

Kicker Amp

Written by: Jim from Oklahoma on October 9, 2013

Crutchfield Customer Review (What's this?)

I just had this amp installed in my 2013 Toyota Tundra Crew cab. It sounds great!!! I have it connected the factory radio and speakers for the time being and plan to upgrade both sets of speakers soon. I have been an Alpine guy my entire life. This is the first time I've ever bought anything but Alpine and am very pleased. Right now the amp is too strong for the factory speakers so the gain is turned down very low, but there is a big difference in quality and volume. I am very happy with this amp and with Crutchfield. I can't wait to get the speakers so I can turn it up a little louder. I really just wanted something to give me a little more umph and I certainly found it. I am assuming it will be a loud amp, as I said before the gain is only up a quarter, maybe, of a turn from the lowest setting.

Pros: Great amp, nice to look at, plenty of power for my use, great price.

Cons: None that I can think of.

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Four 2" Self-tapping screws
  • 4 Flat washers
  • 3mm Allen wrench
  • Owner's Manual (English/ French/ Spanish/ German)
  • Power certificate

Product Research



Class D Amplifier Design: The Kicker KX400.4 is a full-range Class D amplifier, which uses digital switching to amplify audio signals. This design results in high efficiency and less heat. The Class D design also allows the KX400.4 to have a small footprint for increased cargo space.

CEA-2006 Compliant: CEA-2006 is a system of testing and measurement methods for mobile audio amplifiers. This voluntary standard advocates a uniform method for measuring an amplifier's RMS power output and signal-to-noise ratio. The criteria for measuring power uses a DC input voltage of 14.4 volts and the RMS power output is measured into a 4Ω load, with 1% or less Total Harmonic Distortion plus noise (THD+N), and over a frequency range of 20 Hz to 20 kHz (for full range amplifiers). Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4Ω. CEA-2006 allows consumers to compare car amplifiers and receivers on an equal basis. Using CEA-2006 criteria, the Kicker KX400.4 is rated at 50 Watts RMS x 4 channels with a 75 dBA signal to noise ratio.

Specifications: The manual also lists these non CEA-2006 compliant specifications:

  • Power:
    • 2Ω: 100 watts x 4 channels (no more than 1% THD+N, 14.4 volts)
    • Bridged: 200 watts x 2 channels (into 4Ω with no more than 1% THD, 14.4 volts)
  • Signal to Noise Ratio: 95 dB (at rated power)

Kicker Livin' Loud Certified Power: The amplifier comes with a certificate that indicates the total maximum RMS power output of the particular amplifier, along with the model number, serial number, and whether the amplifier passed the total harmonic distortion, signal-to-noise ratio, and protection circuit tests.

Auto Turn-On: The Auto Turn-On switch offers three options:

  • +12 V: The amp turns on when +12 volts is applied to the remote terminal.
  • DC Offset: The amp turns on when a 6 volt offset is detected on the signal inputs (from a speaker-level source); in this mode the amp's remote terminal acts as a +12 volt output to turn on another component.
  • Audio: The amp turns on when an incoming audio signal is detected; in this mode the amp's remote terminal acts as a +12 volt output to turn on another component.

Protection Circuitry: The KX400.4 has protection circuitry that will turn the amp off in the event of overheating, over voltage (power input), under voltage (power input), short circuit (speaker output), and over current (speaker output). If the Protection LED on the front side of the amp illuminates red, the protection circuit has engaged and the amp will not play until the problem is resolved.


Gain: To accommodate the varying range of signal levels coming from today's factory and aftermarket radios, the Kicker KX400.4 features adjustable gain controls (low level: 125mV-5V, high level: 250mV-10V). The front and rear sections of the amplifier (Amp 1 and Amp 2) have independent rotary gain controls, labeled from 0 to 11.

Input Level Switch: Set the input level switch to Lo when using preamp level input signals and Hi when using speaker level input signals.

Crossover: The front and rear sections of the amplifier also have independent crossover circuits:

  • Amp 1:
    • Mode: three position switch; Off (crossover bypassed), HP (high-pass), or LP (low-pass)
    • Range: two position switch; sets the frequency adjustment range for the crossover point dial; 1x (10-500 Hz) or 10x (100-5,000 Hz)
    • Frequency: continuously variable from 10 to 500 Hz (with Range switch in the 1x position) or 100-5,000 Hz (with Range switch in the 10x position)
  • Amp 2:
    • Mode: four position switch; Off (crossover bypassed), HP (high-pass), LP (low-pass), or BP (band-pass, both high-pass and low-pass circuits engaged)
    • Range: two position switch; sets the frequency adjustment range for the low-pass crossover point dial; 1x or 10x
    • High-Pass Frequency: continuously variable from 10 to 500 Hz
    • Low-Pass Frequency: continuously variable from 40 to 500 Hz (with Range switch in the 1x position) or 400-5,000 Hz (with Range switch in the 10x position)

Fader: When your source unit has discrete front and rear outputs, set the fader switch to on. Turn the fader switch off to send a single stereo input to both the front and rear amps.

KickEQ: The amplifier's KickEQ bass boost circuits are continuously variable from 0 to +18 dB and centered at 40 Hz. The front and rear amps have separate bass boost controls.


Power Connections: The power and ground connections are set-screw terminals that will accommodate up to 4-gauge wire. The remote turn-on set-screw terminal will accept up to 8-gauge wire. The included Allen-wrench is required to loosen/tighten the terminals.

Note: The Amplifier is not equipped with an internal fuse. An external 80-amp fuse (not included) must be installed on the power wire. If the system has only this amp and a wiring kit is used that includes a fuse with a value other than 80-amps, the original should be replaced with an 80-amp fuse.

Speaker Outputs: The Kicker KX400.4 is equipped with four pair of set-screw terminals. The terminals will accommodate up to 8-gauge wire and are loosened/tightened with the included Allen-wrench.

Dual Sensitivity Inputs: The KX series amplifiers have dual input sensitivity differential RCA inputs, which will accept either speaker-level (high) or RCA (low) signals from your car's head unit. A high-level signal can be run from the head unit's speaker outputs to the stereo RCA inputs of the amplifier using Speaker Wire to RCA adapters (206KiSL, sold separately). The Input Level Switch on the amp should be set to high when using a speaker-level input, and low when using an RCA line-level input.

Line Level Output: The amplifier has a pair of RCA line level outputs for feeding another amplifier. This is the same signal that is present at the amp's inputs. Either input method (speaker-level or RCA) will provide a low-level output signal to the RCA outputs. The amplifier's crossovers have no effect on the line level output signal, however, if you input a filtered signal from the head unit, the amp's low-level output will also be filtered.

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.

Customer Q&A

1 question already asked

THe total output , certified power is 483 wts rms [ JON  Oct 16, 2015 ]
I wish i could help but i'm on vacation in Germany and dont have access to any of my information. Bob [ Bob  Oct 16, 2015 ]