Small amp — big power

Polk's PA D4000.4 4-channel amplifier may be small, but it can power your front and rear speakers with up to 125 watts RMS each. Or, you can switch this little beast over to 2-channel mode to drive a couple subwoofers with up to 200 watts RMS each. However you use it, this amplifier will fit in almost any location in your vehicle because of its convenient size and shape.

Great looks and a clear voice

Polk developed and employed their full-range Class D amp technology that helps this amp reproduce music very cleanly, with no added coloration or distortion. Separate high- and low-pass filters on the front and rear channels allow this versatile amp to run a variety of speaker systems, like bi-amped mid-bass and tweeter components, or two front speakers and a sub. This amp's tough, good-looking stainless steel case won't tarnish, even in extremely humid conditions.

Product Highlights:

  • 4-channel car amplifier
  • 125 watts RMS x 4 at 4 ohms (200 watts RMS x 4 at 2 ohms)
  • 200 watts RMS x 2 in bridged mode (4-ohm stable in bridged mode)
  • separate variable high-pass filters for front and rear channels (20-4000 Hz, 12 dB per octave)
  • separate variable low-pass filters for front and rear channels (50-5000 Hz, 12 dB per octave)
  • preamp inputs
  • fuse rating: 30A x 2
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 11-3/4"W x 1-13/16"H x 6-3/4"D
  • warranty: 1 year
  • 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.

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Hands-on research

What's in the box?

Download owner's manual

  • Four channel amplifier
  • Two 35 amp ATO fuses (1 installed/ 1 extra)
  • Two 40 amp ATO fuses (1 installed/ 1 extra)
  • Four 1" Self-tapping screws
  • Owner's manual (English/ French/ Spanish/ German/ Italian/ Portuguese)
  • On-line product registration information

Product Research



Input Mode: Set the input mode switch to 4-channel when using four outputs from your head unit, set to ST (stereo) when using two outputs from your head unit.

Front/Rear: The front and rear sections have independent controls for gain and crossover settings:

  • Level Control: rotary gain controls; continuously variable from 200 mV to 6 V
  • Crossover Mode Switch: The crossover has three mode options:
    • Full: crossover is bypassed
    • HPF: High Pass Filter
    • BPF: Band Pass Filter, both the high pass and low pass crossovers are engaged, useful for powering midrange speakers, or a subwoofer with the high pass crossover used as a sub-sonic filter
  • High Pass Crossover Frequency: the high pass crossover points are continuously variable from 20 Hz to 400 Hz, or 200 Hz to 4 kHz, depending on the frequency multiplier switch
  • High Pass Frequency Multiplier: 2-position switch; specifies the variable high pass crossover point range; 20 Hz to 400 Hz (x1), or 200 Hz to 4 kHz (x10)
  • Low Pass Crossover Frequency: the low pass crossover point is continuously variable from 50 Hz to 500 Hz, or 500 Hz to 5 kHz, depending on the frequency multiplier switch
  • Low Pass Frequency Multiplier: 2-position switch; specifies the variable low pass crossover point range; 50 Hz to 500 Hz (x1), or 500 Hz to 5 kHz (x10)


Power/Ground: set screw terminals; accept bare speaker wire up to 4 gauge (4 gauge wire recommended)

Remote Turn-on: set screw terminal; accepts bare speaker wire up to 8 gauge

Speaker Terminals: four pair of set screw terminals; accept bare speaker wire up to 8 gauge

Line Level Inputs: two pair of nickel-plated stereo RCA jacks

Fuses: one 40-amp and one 35-amp ATO fuse

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.