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Our take on the Rockford Fosgate Power T400X4ad

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: play the setup tone on the included test CD, 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. The optional PLC2 remote level control also doubles as a clip indicator, so you can see from the front seat if your music's clipping.

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 test tone CD
  • 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)
  • optional PLC2 Punch Level Control wired remote with clip light available
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)
  • Our 60-day money-back guarantee

I Love This Amp This Is The Best Amp I've Ever Owned Totally Awesome !

Willie, Moreno Valley Ca.

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)
  • Setup disc CD-ROM
  • Amplifier Quick Setup sheet
  • Certificate of Performance Verification

Rockford Fosgate Power T400X4ad Reviews

Average Customer Review(s):

(6 Reviews)

T400x4 ad

Willie from Moreno Valley Ca. on 8/31/2017

I Love This Amp This Is The Best Amp I've Ever Owned Totally Awesome !

Pros: Crisp Clear Clean Sound No Distortion.

Cons: Small Compact Easy To Mount.

Awesome amp

Chico from Belvidere, IL on 5/3/2016

Crutchfield Customer Review (What's this?)

I really love this product

Pros: Everything about is good

Cons: This price that sucks

Best amp I've ever owned

Rob from Florida on 10/1/2015

Crutchfield Customer Review (What's this?)

Excellent, runs cool as a cucumber and please do not compare this to the PBR amp, it's like comparing apples to oranges.

Pros: Crisp Undistorted sound Runs cool with built in fans

Cons: No cons


Subdoc from Kingsland GA on 9/17/2015

Crutchfield Customer Review (What's this?)

Amazing product and fit on my 2013 Flhtk Harley Davidson. Currently pushing 4 speakers upper and lowers and producing rich full sounds at every speed. Can not recommend this product enough. Crutchfield once again delievers on time for the best price around ......the only place I shop. Thanks again for helping make all my rides rock.

Pros: Powereful unit 4 cannels Own cooling system Small foot print Very adjustable

Cons: None

Great little amp!

Milton from California on 6/25/2015

Crutchfield Customer Review (What's this?)

Great little amp! It's $$$ but you get what you paid for! I try the Focal FD, but it just don't cut it for me!

Pros: Super small for that kind of power. Fan cool.

Cons: Little bit pricey! Would be great if it have build in processors!

My T400xad

K.A.M. from Miami, FL on 3/20/2015

Crutchfield Customer Review (What's this?)

Beautiful service for this wonderful product. Thanks




Hands-on research

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.

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

Crutchfield asked  
Why did you buy this?

very good line of amps and good features[ Michael  Mar 04, 2017 ]
1. Good name. Looks like a great 100W amp. 2. Molex plugs will make for easy and clean install - you can buy your own molex pins and then you won't have to splice the pigtails.[ Frederick  Aug 26, 2016 ]
This amp will be a perfect match to my Focal speakers.[ William  Feb 14, 2016 ]

1 question already asked

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 ]