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Rockford Fosgate Prime R300X4

4-channel car amplifier — 50 watts RMS x 4

Item # 575R300X4

Rockford Fosgate performance in a small package.

Find what Fits your vehicle

Rockford Fosgate performance in a small package.

Discontinued item
6 questions - 8 answers

Item # 575R300X4

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About the Rockford Fosgate Prime R300X4

Rockford Fosgate power for your speakers

Rockford Fosgate performance in a small package. The Prime Series R300X4 4-channel amp can drive your speakers with 50 watts RMS each, so you'll really feel your tunes rockin'. Or, you could switch the R300X4 to 2-channel mode to run a couple of subs with 150 watts RMS each — when you buy a bigger amp for your subs later on, you can still use this 4-channel to drive all your speakers. Smart move.

Rockford Fosgate power for your speakers

Rockford Fosgate performance in a small package. The Prime Series R300X4 4-channel amp can drive your speakers with 50 watts RMS each, so you'll really feel your tunes rockin'. Or, you could switch the R300X4 to 2-channel mode to run a couple of subs with 150 watts RMS each — when you buy a bigger amp for your subs later on, you can still use this 4-channel to drive all your speakers. Smart move.

You can use the high- and low-pass filters and Rockford Fosgate's famous Punch boost to get maximum performance from the speakers in your vehicle. And speaker-level inputs let you hook this amp up to almost any system, even a factory stereo.

Rugged performance and value

The R300X4's heavy cast-aluminum chassis efficiently draws damaging heat away from its internal components, ensuring reliable, long-term play. The amp's built-in sensors keep track of the output current and power supply temperature, ensuring that plunging speaker impedances (they change constantly during play) or even a short circuit won't hurt anything. Your driver's seat will become your favorite place for listening to music once this Prime amp goes to work.


Product highlights:

  • 4-channel car amplifier
  • 50 watts RMS x 4 at 4 ohms (75 watts RMS x 4 at 2 ohms)
  • 150 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • variable high- and low-pass filters (50-250 Hz, 12 dB/octave) on front and rear channels
  • selectable bass boost (0, 6, 12 dB at 45 Hz)
  • Class-AB amplifier design
  • MOSFET power supply
  • frequency response: 20-20K Hz
  • preamp and speaker-level inputs
  • 8-gauge power and ground leads and a 50-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 50-amp in-line fuse between the distribution block and this amplifier is recommended
  • 13-1/4"W x 2"H x 7-3/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee
  • MFR # R300X4

What's in the box:

  • 4-Channel amplifier
  • Two 6" Speaker level input harnesses
  • 3mm Allen wrench
  • Four 3/4" Self-tapping screws
  • 4 Flat washers
  • Installation & Operation manual (English/ French/ Spanish/ German/ Italian)
  • Amplifier verification certificate

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More details on the Rockford Fosgate Prime R300X4

Mark G.

Product Research



Overview: The front and rear sections of the Rockford Fosgate Prime R300X4 4-channel amplifier are bridgeable, so it can be wired in 4-channel, 3-channel, or 2-channel mode.

CEA 2006 Compliant: The R300X4's power ratings and signal to noise ratio are measured according to the uniform standards advocated by the Consumer Electronics Association (CEA). This allows you to accurately compare these specifications for all CEA 2006-compliant amplifiers, even from different brands. Manufacturers who adhere to these standards can display the CEA 2006 logo on their products and packaging. CEA2006 Specifications for this amplifier are:

  • 4 Ohms: 50 watts RMS x 4 at 4 ohms, 14.4 volts, and less than 1% THD+N
  • 2 Ohms: 75 watts RMS x 4 at 2 ohms, 14.4 volts, and less than 1% THD+N
  • Bridged: 150 watts RMS x 2 at 4 ohms, 14.4 volts, and less than 1% THD+N
  • S/N: 80 dB, measured at 1 watt output (100 dB measured at rated power)

LED Indicator: The amplifier is equipped with an LED power/protect indicator. The LED illuminates blue when the unit is turned on. It illuminates red if the thermal or short circuit protection circuit is engaged, and the amplifier will automatically turn off.

Mounting: The amplifier can be mounted vertically or horizontally using the supplied mounting screws. The amplifier should never be mounted in an engine compartment as this will void the warranty.


Gain Controls: The front and rear amplifier channels have independent gain controls. Each rotary control is labeled 1 to 11 and has a sensitivity range of 150mV to 4V when using the RCA inputs, 450mV to 12V when using the speaker level inputs.

Crossover: There are also independent 12 dB/octave crossovers for the front and rear channels. Crossover switches allow you to choose low-pass, high-pass, or full-range operation. The crossover points are continuously variable from 50 to 250 Hz.

Punch EQ: The Punch EQ bass boost circuits are individually selectable, 0 (flat), +6 dB, or +12 dB and centered at 45 Hz.

Input Switch:

  • 2-CH: when using only the front inputs
  • 4-CH: when using the front and rear inputs


Power Terminals: The power and ground terminals are nickel-plated set screw terminals and will accommodate up to 4 gauge power and ground wires.

Fuse: An external 50-amp fuse (not included) must be installed on the power wire at the battery. If a wiring kit is used which includes a fuse with a value other than 50-amps, the original should be replaced with a 50-amp fuse.

Remote Terminal: The remote turn-on terminal is a nickel-plated set screw terminal that will accommodate up to an 8 AWG wire. It's used to remotely turn the amplifier on and off.

Speaker Terminals: The four pair of speaker outputs are nickel-plated set screw terminals what will accommodate up to 8 AWG speaker wire.

RCA Input Jacks: Front and rear RCA input jacks provide an easy connection for preamp level inputs. They are nickel-plated to resist signal degradation caused by corrosion.

Speaker Level Input: Two speaker level input harnesses are included, making it easier to add the amplifier to a factory radio or to a receiver with no preamp outputs.

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Customer Q&A

6 questions already asked

If i use speaker level input can i still chain a second amp off the RCA output?
[ Ralph  Aug 25, 2019 ]
1 answer
I'm not entirely sure, but I don't think so. The RCA pass through would be connected to the second pair, so it might only work with RCA inputs
[ Markarid  Sep 16, 2019 ]
Can I run a set of Memphis prx462 speakers with this amp ?
[ Hondoman  Dec 08, 2016 ]
1 answer
I'm going to go ahead and recommend that you try an amp with a lower rms output. This amp pushes way more than what you actually need and you could probably go a lot cheaper as well and get great sound. If you are running 4 of these I would get a four channel amp around the 100-150 rms range. If you are running only 2 I would stick to an amp with an output no more than 100 and I would really try to find one at 60 if you can. I hope this helps at least a little!
[ Cody  Dec 09, 2016 ]
Do I need to run anew wire pair from each speaker to this amp? Instead is there a way not to run new set of wires from each speaker & simply switch the speaker wires from factory radio?
[ nrupvin  Mar 16, 2016 ]
2 answers
Should be no problem using factory wires
[ DENNIS  Mar 17, 2016 ]
THis is personal preference, you can use factory wiring, you'll just need to map out the color codes on wires to get your front and back left to right correct. Typically factory wiring is small gauge wiring, a lot of people prefer large diameter wires, believe to increase sound quality. I prefer larger than factory wires. But it's a lot of work and extra money. Most cases factory should be fine tho. I first noticed difference in sound quality in home stereo, using monster cable instead of small gauge. My ears seem to like bigger cables. Hope this helps
[ Richard  Mar 16, 2016 ]
I am looking to use this in my garage, hooked up to a car stereo. The 12v power will come from an old computer power supply (psu). What I need to know is how many watts power do I need? Why does the 'details' tab of this product not list the peak output? What is the max output?
[ David  Dec 27, 2015 ]
1 answer
How much watts you need depends on the speakers you plan on using. This amp is 75x4 rms. I'm no expert but usually the peak output is about double the rms. I have the gain set at about 1/2 for front and rear components that rate 50watts rms. it's way more than enough, but allows for future upgrades
[ Nathan  Dec 28, 2015 ]
can you run, say, the front speakers at 4 ohms and the rears at 2 ohms instead of same impedance all around?
[ Thomas  Sep 14, 2014 ]
2 answers
I don't think so.
[ JESSE  Sep 24, 2014 ]
We have not received any answers from other customers on your question. I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They should be able to help answer your question.
[ Krissy  Sep 16, 2014 ]  Staff
I'm installing to a factory stereo with 4 new door speakers. Will I still need LOC's (line out converters) with this AMP?
[ Chris  Aug 05, 2014 ]
1 answer
I forwarded your question to an Advisor and they responded with the following: The amplifier has speaker level inputs, so you do not "need" an LOC. It can still help if you want to get the cleanest signal to your amplifier from the factory radio. If you would like to discuss further you can contact an Advisor directly by phone (1-800-324-9695) or online chat.
[ Krissy  Aug 06, 2014 ]  Staff

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