This product is a vintage Polk model and is not available for sale, but it may still be available in some stores as a closeout or used product. The following text is taken from the original sales brochure for this product and does not reflect current availability. If you happen to have any question or concerns about this product, or any other Polk Audio product, feel free to contact our Customer Service Department at 1-800-377-7655 Monday - Friday, 9am - 5:30pm EST

C400.4 (4/3/2 Channels)

4/3/2 Channel Power Amplifier

Available Finishes:

Championship Performance


"The C400.4 makes great power, looks totally cool and comes in a tight package. The amp exceeds its power ratings in all categories by a significant margin...this amp is a hit." - Performance Auto & Sound, Feb. 2005

"The higher-current through-hole components are better quality, using tighter tolerances. There are lots of film capacitors in the signal processing sections, and all of the switches and potentiometers have a nice feel to them. These components are all mounted on a true double-sided fiberglass circuit board." - Car Audio & Electronics

When I swapped out my (Brand X) for the Polk amps, I was doing it strictly so that my amps and subs would match. Boy, was I surprised when my components sounded better then they ever have before! They were crisper and tighter then any amp I had put on the speakers previously. Polk amps are definitely some of the best amps I have come across in my almost ten years of being in the car audio market and I would suggest them to anyone from the entry level customer to the out-most enthusiast!" - Lynn Ramp, Award-Winning Competitor

Ditch your passive Xover: Bi-Amp with the C400.4

With the C400.4, you can power a pair of Polk/MOMO (say that four times fast!) Components using the active crossover inside the amplifier instead of the speaker system's passive crossover. Ditch those passive crossovers and wire up your MMC Series Components directly to this amplifier. Then press the C400.4's Pre EQ Switch and instantly get greater dynamic range and higher efficiency with your MMC Series Speakers. Love to tweak and tweak again? Audio perfectionists would die to have this feature on their amps. You could be one of them. And you don't have to die. This time.

Championship Performance means: More Power. Better Sound. More Control. Built To Be The Best.

More Power.

  • Polk's Massive Dynamic Headroom (MDH) Power Supply uses multiple smaller-value capacitors wired in parallel to lower the Equivalent Series Resistance (ESR). This lowers impedance for more efficiency, faster transient response, more instantaneous power peaks, tighter bass and better control.
  • The MDH Power Supply features oversized Toroidal Transformers to more easily deliver high voltage, high current power. This set of tremendous transformers lowers the incidental radiation of stray magnetic fields for uncontaminated audio signals.
  • Oversized Power Supply BUS Bars achieve maximum power transfer from the MDH Power Supply to the audio circuitry for more efficient high voltage, high current output stages.

Better Sound.

  • Power Supply “Chokeâ€? Inductor reduces stray noise effects from power cables and alternators, cutting ground loop disturbances for truly quiet amp performance.
  • High current Bipolar Output Transistors with low impedance pump maximum voltage and high-current to your speakers. Dual low noise Operational Amplifiers at the input gain stages deliver higher gain & wider bandwidth at a faster “slewâ€? rate (with the ability to change voltage “on the flyâ€?), for excellent transient response.
  • High-end Non-Inductive Metalized Film Capacitors in the active filter stages for excellent transient response and extended bandwidth with low noise and low distortion.
  • Surface mounted Metal Film Resistors are used in the audio signal path, delivering higher performance with lower noise and less fluctuation (“value driftâ€?) over time. MFR technology is so stable that your music will sound perfect for the life of your amp.
  • High damping factor at the speaker output terminals improves driver control for tighter, punchier bass.

More Control.

  • While most amps have an input sensitivity up to only about 2 Volts, Polk's Variable Input Sensitivity ensures high performance even with older, low-power head units by accepting 200mV up to 8 Volts, and allowing Line Level (RCA) or Speaker Wire inputs.
  • Fully adjustable electronic crossovers power any install using virtually any speakers on the market.
  • The exclusive Polk/MOMO Pre-EQ Switch optimizes the amp's active crossovers for use with Polk/MOMO Ultra High Performance Speakers and Subwoofers for perfect sound every time! In the C400.4, Pre-EQ is an auto-preset filter (2nd Order HP, Fc 5.5kHz, Q of 0.707; 2nd Order LP, Fc 3kHz, Q of 0.707; 3rd order HP, Fc 50Hz, Q of 0.707; Notch Filter, Fc 11.7kHz, Q of 5.5, -2dB) that replaces the MMC Series passive Xover, and provides greater dynamic range and efficiency with MMC Series Speakers.
  • Remote Subwoofer Level Control available separately.

Built To Be The Best.

  • Industrial-strength extruded aluminum, supremely rigid and warp-resistant, with excellent heat dissipation for more reliable performance. Styled in conjunction with MOMO, maker of the world's most sought-after bolt-on accessories, and featuring real Carbon Fiber accents.
  • 6-Way Smart System Protection (SSP) circuits: Power and Ground-Reversal Protection, Thermal and Short Protection, Current Overdraw and Low Impedance Protection circuits with auto-Standby Mode ensure safety, reliability and durability.
  • Selectable Subsonic Filters (15Hz@24dB/octave) for an extra level of speaker protection. Select ON/OFF via internal jumpers to keep subsonic frequencies from reaching drivers, preventing driver damage at high levels of low frequency play and reducing stress on the power supply for extreme reliability.
  • Dual (top and side) computer optimized extruded aluminum Heat Sinks for more efficient power output, superior heat dissipation and high reliability.
  • Double Layer Fiberglass Epoxy Printed Circuit Boards for more rigidity and less shrinkage, with plated through-holes instead of jumpers, for twice the amount of component contact area. Efficient layout safely packs more circuitry, with tighter component tolerances, into a smaller circuit board for a smaller overall amp footprint.
  • Removable cast aluminum End Caps offer more flexible install options, including an even smaller amp footprint.
  • Power, Thermal and Short Protection LEDs easily visible on top plate.
  • Hideaway Cover Plate conceals the wiring and the "Set It Once" user-adjustable controls for clean-looking, fiddle-free installs.


Total Frequency Response< 10Hz to 45kHz 
Signal-to-noise (Referenced to rated power)105 dBA
Remote Gain0 to -30dB 
Protection CircuitryPower and ground reversal, Thermal and Short, Current Overdraw and Low Impedance Protection with auto stand-by mode 
Subsonic Filter24dB/Octave @ 15Hz 
High Pass Filter
Filter Slope12db/oct. or 24dB/oct. 
Filter Frequencyadjustable 50Hz - 5kHz 
Low Pass Filter
Filter Slope12db/oct. or 24dB/oct. 
Filter Frequencyadjustable 50Hz - 5kHz 
Input Impedance10.0000 k ohms
Output Impedance0.0200 ohms


Product Weight (each)13.50 pounds
With Panels
Height2 1/2" (6.35cm) 
Width16" (40.64cm) 
Depth9 3/4" (24.77cm) 
Without Panels
Height2 1/2" (6.35cm) 
Width15 1/2" (39.37cm) 
Depth9 3/4" (24.77cm) 

Amplifier Specs

Channel Notes4/3/2 (bridgeable) 
Total Dynamic Power975 watts
12V & Ground Cable Gaugeaccept up to 4 AWG wire 


Total Shipping Weight15.00 pounds

Amplifier Power Specs

RMS Power at 14.4V
Watts per channel NOT bridged @ 1 kHz
4 ohms75 watts
2 ohms100 watts
Watts per channel bridged
4 ohms200 watts

Specifications, dimensions and features subject to change without notice. For more information call us at 1-800-377-7655 (USA and Canada). Outside of North America call +1 (410) 358-3600.

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C400.4 (4/3/2 Channels) Accessories