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Rockford Fosgate Power T400X4ad Compact 4-channel car amplifier — 100 watts RMS x 4

Item # 575T400X4A

Rockford Fosgate's Power Series T400X4ad 4-channel amplifier can send up to 100 watts RMS to four separate...

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Rockford Fosgate's Power Series T400X4ad 4-channel amplifier can send up to 100 watts RMS to four separate...

9 questions - 17 answers

Item # 575T400X4A

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About the Rockford Fosgate Power T400X4ad

Buck Pomerantz

Super-compact, bursting with power

Rockford Fosgate's Power Series T400X4ad 4-channel amplifier can send up to 100 watts RMS to four separate speakers, or you could use this tiny powerpack to run a couple of subs with 200 watts each. A dual-fan forced air cooling system keeps this sturdy little amp from overheating, so it can play hard for a long time.

Super-compact, bursting with power

Rockford Fosgate's Power Series T400X4ad 4-channel amplifier can send up to 100 watts RMS to four separate speakers, or you could use this tiny powerpack to run a couple of subs with 200 watts each. A dual-fan forced air cooling system keeps this sturdy little amp from overheating, so it can play hard for a long time.

Class AD: accurate and powerful

Rockford Fosgate uses their proprietary Class AD amplifier technology, combining the high fidelity of a Class A system with the high efficiency of their special Class D technology, to bring you this ultra-efficient, high-output amplifier. In other words, this compact amp produces more power with less current draw from your vehicle's charging system than most other amps on the road today.

Rockford Fosgate's high-tech solutions yield more power

Power Series amplifiers actively monitor speaker performance using Rockford Fosgate's Constant Power technology. A speaker's impedance naturally fluctuates as it performs, fighting against your amp's output. So, just like your cruise control increases the engine's RPM to maintain your car's speed uphill, Constant Power maintains this amp's output by increasing its internal voltage and current flow when the speaker's impedance rises. This results in up to a 25% increase in the amp's total power output.

Rockford Fosgate T400X4ab

T400X4ab control panel with clip lights

Easy to set for optimum performance

Rockford Fosgate's C.L.E.A.N. technology (Calibrated Level Eliminates Audible Noise) setup system ensures your music will sound as clean and powerful as possible. It works like this: first download the setup tones from Rockford Fosgate, then play the tone, adjust the receiver volume until a red clip light on the amp goes out, then turn the amp gain up until a blue light comes on. It's that simple — your amplifier will be perfectly set to match your receiver's output. When your receiver reaches maximum clean volume, you'll get maximum clean power from your Power amp. At quiet listening levels, you'll hear less background noise and more of your music.

Clip lights

If that blue light turns solid red while you're playing music, the amp's telling you that your source is distorting and you should turn it down, or risk damage to your gear.

Rockford Fosgate T400X4ad

T400X4ad input connections (harnesses included)


Product highlights:

  • 4-channel car amplifier
  • 100 watts RMS x 4 at 2 to 4 ohms
  • 200 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • Class AD amplifier design
  • Constant Power technology maintains full output power despite impedance changes
  • C.L.E.A.N. gain setup system includes clip lights and link to Rockford Fosgate's setup tones
  • differential input circuitry helps eliminate hum
  • dual-fan forced induction cooling
  • variable high- and low-pass filters (50-250 Hz, 12 dB/octave)
  • variable Punch EQ (bass/treble boost: 0-18 dB at 45 Hz, 0-14 dB at 12,500 Hz)
More Info:
  • preamp and speaker-level inputs (quick-connect input harnesses included)
  • signal-sensing turn-on with speaker-level inputs eliminates need for remote turn-on lead
  • 8-gauge power and ground leads and a 60-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 60-amp in-line fuse between the distribution block and the amplifier is recommended
  • 8-5/8"W x 1-5/8"H x 4-5/16"D
  • warranty: 2 years (extends to 3 years when purchased with a Rockford Fosgate RFK8, RFK8i, or RFK4D amp wiring kit)
  • MFR # T400X4AD

What's in the box:

  • Four-channel amplifier
  • Two 14" Input harnesses (4-pin Molex connector to 2 female RCAs)
  • Two 8" Speaker output harness (4-pin Molex connector to bare wire)
  • Amplifier Quick Setup sheet
  • Certificate of Performance Verification

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More details on the Rockford Fosgate Power T400X4ad

Mark G.

Product Research

Warranty Information


Overview: The Rockford Fosgate Power T400X4ad is an ultra-compact four-channel amplifier. Even though the amplifier is only 8-5/8" x 4-1/4", it puts out a full 100 watts per channel at 4 ohms or 2 ohms. In bridged mono, the output is 400 watts at 4 ohms.

Class AD: The amplifier features Rockford Fosgate's proprietary Class AD technology, which allows the amp to produce more power with less current draw. It takes the highly efficient bd amplifier design to a full-range application. Class AD uses Dynamic Frequency Switching to increase the switching frequency during lower output levels for better signal resolution. In addition, Post Choke Feedback Filtering removes unwanted distortion by comparing the input signal to the output signal at the speaker connector.

Constant Power: Rockford Fosgate uses a patented circuit design to gain up to 25% more output power. Constant Power actively increases the voltage and current in direct relationship to the rise and fall of music signals to provide additional power.

Fan Cooled: The T400X4ad features dual fans to keep the amp running cool. Dual Fan Forced Induction pulls in fresh air, which pulls heat off of the MOSFETs, and directs airflow into the exhaust channel and out of the amplifier. Since the top and bottom heat sinks are decoupled, the top remains cool to the touch. When installing, you should leave at least 2-3" of clearance around the ends of the amplifier to optimize air flow to the fan intake and exhaust vents.

C.L.E.A.N. Technology: Using Rockford's C.L.E.A.N. (Calibrated Level Eliminates Audible Noise) technology, you can easily and precisely set up the amplifier levels to eliminate distortion from damaging your speakers. Simple LED indicators are used, instead of test equipment, to identify signal clipping at both the input and output, and to match the audio source to the amplifier.


Top Mounted Controls: The T400X4ad features easy-to-reach controls on the top panel of the amplifier. There are two sets of controls: one for the front channels and another for the rear channels. The controls include:

  • 2/4 Channel Switch: This switch determines which inputs are active. In the 2CH position, only the front inputs are active, allowing you to feed the signal to all four channels with only a two-channel input. In the 4CH position, both the front and rear inputs are active.
  • Input Level: This rotary control lets you match the output of the audio source to the amplifier. A small screwdriver (not included) is required to set the levels.
  • Punch EQ: The Gyrator-based Punch EQ eliminates frequency shift with boost. It works in conjunction with the crossover switch on the amplifier. When set to Low-Pass operation, it functions as a 0 to +18dB variable Bass Boost at 45Hz. When set to High-Pass, it is a 0 to +14dB variable Mid-Bass and Treble Boost at 12.5kHz. When set to All-Pass, the Punch EQ boosts both the bass and treble frequencies. A small screwdriver (not included) is required to set the amount of boost desired.
  • Crossover Switch: This 3-way switch lets you select Low-Pass (LP), High-Pass (HP), or All-Pass (AP) on the Butterworth crossover.
  • Frequency: The crossover frequency is constantly variable between 50Hz and 250Hz with a slope of 12dB/octave. A small screwdriver (not included) is required to set the crossover cut-off frequency.

LED Indicators: The amplifier has three LED indicators on its top panel:

  • Input Clip Indicator: The input clip indicator works in conjunction with the audio source's volume knob. It will illuminate red when the audio source reaches its clipping point.
  • Output Clip Indicator: The output clip indicator works in conjunction with the amplifier's input level knob. It will illuminate red when the output level has reached the clipping point. When setting the level using test tones, you should adjust the output level until the LED glows blue. If setting the output level using music, the LED should glow blue with only an occasional red indication.
  • Power/Protect: The Power LED illuminates blue when the unit is turned on. If the LED turns yellow, a short circuit or too low of an impedance has been detected at the speaker connections. If the LED turns red, the amp has overheated and has shut down.

Left Side of Amplifier:

  • Inputs: There are 4-pin Molex connectors for the front and rear channels that work with the supplied RCA Input Harnesses. The front harness has gray and white wires, while the rear harness has purple and green wires. The amp will accept signals from either high-level (speaker) or low-level (RCA) sources. If connected to a high-level input signal, the amp's auto turn-on feature is active.
Note: For high-level input, you can either splice RCA plugs onto the source unit's speaker wires, or cut the RCAs off of the supplied input harnesses and splice on speaker wires from the source unit using the standard wire color code (front left=white, front right=gray, rear left=green, rear right=purple).

Right Side of Amplifier:

  • Power/Remote Terminals: The amplifier's Power, Ground, and Remote terminals are located in a separate plug-in quick connector. The connector has compression terminals that will accept up to 8-gauge wire. When utilizing high-level signals for the auto turn-on feature is active, and the Remote terminal can be used as an output to turn on/off up to two additional amplifiers or other accessories. A small screwdriver (not included) is required to tighten/loosen the compression terminals. Once the wires are installed in the quick connector, the connector can be plugged into the amplifier.
  • Speakers: Two 4-pin Molex connectors work with the supplied Speaker Output harnesses. The speaker wires can be spliced to the harness' four 16-gauge wires and plugged into the amplifier.
Note: For 2-channel bridged mono operation, the front left + and right - wires and rear left + and right - wires should be used to connect to the speakers (4Ω minimum).
Warranty Information

Warranty Terms: Rockford Fosgate Power-series amplifiers carry a two year warranty, when purchased from an Authorized Rockford Fosgate Dealer.

Extended Warranty Offer: Rockford Fosgate offers a one-year extended warranty (for a total of 3 years) when the amplifier is installed using a matching Rockford Fosgate installation kit, such as the RFK8 or RFK8i.

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Customer Q&A

9 questions already asked

Ok this is probably a dumb question but where do the RCA cables go? Or because it's compact, does it not come RCA applicable?
jerick  Aug 21, 2023
1 answer
Greetings Jerick, and no worries, there are no dumb questions. This amp has a Molex terminals and include adapters from Molex to RCA. There is just no picture of those on our presentation. They are however listed in whats in the box on the overview page.
hogan  Aug 21, 2023 (Staff)
How is the unit mounted? I didn't find any pictures or diagrams that showed the base plate or anything where one might mount. I see the photos from others here that seem like they affixed it to pieces of plastic/poly and whatnot and then attach that to a vehicle surface - but how is it attached to the scrap?
karl  Jan 28, 2023
1 answer
Great question, Karl. The Rockford Fosgate Power T400X4ad amp can be affixed to a surface by the two open tabs on either side of the amplifier. You can mount this vertically or horizontally to fit a wide range of applications. This is also how Rockford mounts the amp to motorcycle or ATV specific mounting plates to use with the T400X4ad amp. Mounting hardware is not included, keep in mind!
bo  Jan 28, 2023 (Staff)
hello. I'm thinking of buying this amplifier for my hertz cpk 690 components in the front and my cpk 165 components in the back. this amp will work for that combination? Cpk 165 (315 peak ,105 continuous) cpk690 (360 peak,120 cotinuous)
alexis  Feb 02, 2022
4 answers
Yes, this amp will work well for your setup.
juan  Feb 04, 2022
Yes, it will be plenty of power.
thomas  Feb 02, 2022
Yes it will work well for them. I currently have it powering 4 Mille legends. One per channel and it as well as the hertz sound amazing!
dustin  Feb 02, 2022
Yes it's a really nice amp with solid crisp delivery
brian  Feb 02, 2022
hello. I'm thinking of buying this amplifier for my hertz cpk 690 components in the front and my cpk 165 components in the back. this amp will work for that combination? Cpk 165 (315 peak ,105 continuous) cpk690 (360 peak,120 cotinuous)
alexis  Feb 02, 2022
3 answers
This amp would be great for those speakers. 100 watts x 4 with good crossovers. Very small size also, so it fits anywhere.
richard  Feb 04, 2022
Yes, this amp would be a perfect fit for your speakers. It's pushes 100w RMS per channel, which is right where your speakers are rated. You always want to match your speakers' RMS wattage to the amp's RMS wattage. I am super happy with it, and I'm sure you will be as well. Sidenote... This thing is TINY! Plus it comes with connectors so you're not having to mess with tiny terminals to plug in the wires.
babak  Feb 04, 2022
Yeah that will be plenty of power fornyour cpk's. I have some Hertz cento comps getting 125W @4 ohm and they are rated for 95w and they love it.
preston  Feb 04, 2022
What is needed to install 4 channel amp and a powered sound ordnance sub on a Tacoma stock radio?
edward  Aug 04, 2021
1 answer
This will depend largely on your vehicle. For details on installation please contact an Advisor by phone (1-800-324-9695) or online chat. They will be able to pull up your vehicle and give you the details on what you will need for an installation.
thomas  Aug 06, 2021 (Staff)
Will 4 gauge wiring kit work with this amp?
yuri  Jan 05, 2021
2 answers
Truth be told, I had a professional installer do the work. After sound proofing my doors and installing all the speakers (Infinity reference speakers) myself in my Sprinter van I just couldn't figure out how to get all the wires to the head unit in the dash. After looking at the battery, I believe they used the wiring kit I supplied, but I can't be absolutely positive. I can tell you that with the addition of that amp and a small sub woofer the sound is now amazing!
collin k  Jan 05, 2021
Yes, probably is even overkill.
roland  Jan 05, 2021
What is the maximum pre amp voltage it can accept?
james  Dec 02, 2020
2 answers
To be honest I'm not sure, I'm running that amp to a component speaker setup and 2 rear alpine 6.5. It over heats not literally to where it shuts down but it's tends to get very hot to the touch
anthony  Dec 04, 2020
The truth is, I don't know! I bought it to power new speakers that installed in my Mercedes Sprinter while still keeping the original Mercedes radio \ head unit. With this this amp and sound proofing the whole cab area we can finally hear music and talk without shouting. Hope this helps, stay safe
collin k  Dec 04, 2020
What if I don't have a cd receiver?
michael  Jul 04, 2020
2 answers
I don't have one either cd receiver it works great with my retro stereo . its a great amp but I up graded to there T-series amps I like them more
pierre  Jul 06, 2020
Get the jl audio bluetooth adaptor works great.
fidel  Jul 04, 2020
has anyone put this amp on a Harley Street Glide. How well do you like it and what kind of speakers do you have?
glenn  May 31, 2014
1 answer
I put this amp in a 2014 street glide special. The amp is great and very easy to setup. I am running Hybrid Audio Texhnologies 6.5's in the faring and Hybrid Audio Texhnologies 5x4's in the bad lids. Sound us loud and super clear. I had to do a little water proofing of the amp though due to the new vent being directly over the amp.
robert  Jun 01, 2014

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