Rockford Fosgate PBR300X4

Compact 4-channel car amplifier — 75 watts RMS x 4

Item #: 575PBR3004

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21 Reviews

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You won't believe how small and powerful this amp is. Rockford Fosgate's PBR300X4 4-channel amp puts out 75 watts RMS to each of your front and rear speakers, giving you the power to fill your listening space with great-sounding music.

Boosted Rail (BR) amp technology
This Punch Class BR amplifier generates this power from a very tiny case — literally the size of your hand. Boosted Rail (BR) amp technology uses capacitors and high-speed circuitry to boost the amp's power supply voltage, when needed, so it can handle musical peaks without missing a beat. Rockford Fosgate uses this new technology to create a remarkable amp that fits almost anywhere and delivers powerful sound.

Heat management
The amp also features speaker-level inputs with signal-sensing turn-on, allowing you to connect into almost any system without having to run a turn-on lead back to the receiver. An extruded aluminum heat sink combines with Rockford Fosgate's heat management technology to make sure your tunes keep rockin' — even when you're playing loud.

Product Highlights:

  • 4-channel car amplifier
  • 75 watts RMS x 4 at 4 ohms
  • non-bridgeable, 4-ohm stable per channel
  • CEA-2006 compliant
  • Boosted Rail amp technology
  • Dynamic Thermal Management cooling system
  • selectable high- and low-pass filters (80 Hz, 12 dB/octave)
  • differential-balanced inputs eliminate noise from your vehicle's electrical system
  • preamp and speaker-level inputs
  • 10-gauge power and ground leads and a 30-amp fuse recommended — wiring and hardware not included with amplifier
  • no onboard fuses — when installing multiple amps in a system, an additional 30-amp in-line fuse between the distribution block and the amplifier is recommended
  • dimensions: 6-15/16"W x 1-9/16"H x 4-5/16"D
  • warranty: 1 year (extends to 2 years when purchased and used with Rockford Fosgate's RFK10 or RFK10i amp wiring kit)
  • 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.

Rockford Fosgate PBR300X4 Reviews

Average Customer Review:

21 reviews
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Quality, I am really satisfied.

Written By Russ, Kansas City, KS on Wednesday, January 21, 2015

Crutchfield Customer Review (What's this?)


Works good

Written By tom, new meadows, ID on Thursday, November 27, 2014

Crutchfield Customer Review (What's this?)

Works very well and it was easy to install

Pros: the quality of the sound is so much better vs. factory

Cons: I think when i turn up the volume to much the amp cuts out to protect the system

Rockford Fosgate PBR300Xr

Written By Mike, Charlottesville, VA on Monday, November 17, 2014

Awesome unit

Great Amplifier

Written By Phil, Marion, OH on Tuesday, April 29, 2014

Crutchfield Customer Review (What's this?)

Definitely woke up my old system in my 2001 Jeep Cherokee with just 4 speakers. Very Happy with this amp and it is very easy to tuck away in small places. Thanks!!!

Great little amp.

Written By Brad, Billings, MT on Monday, February 24, 2014

Crutchfield Customer Review (What's this?)

I have an open top '69 Beetle with a V8 motor. The exhaust is loud and I could not hear the music over the exhaust. So I called Crutchfield and they recommended this amp as space is very limited. This amp fits well in tight places and did the job. This amp lets me listen to music clearly now when going for that sunny afternoon drive.

Pros: Small and easy to hide. Great power for such a little package.

Cons: Non self installing.

Rockford Fosgate PBR300X4

Written By Anonymous, Seneca, MO on Wednesday, February 05, 2014

I have with this amplifier a system with amazing clarity. I can turn the system up and there is no distortion. My F150 extended cab has concert quality sound.

Pros: The size of the amplifier allows it to be hidden. I drove for over ten hours and this amplifier provided the music without any problems.

Rockford Fosgate PBR300X4

Written By Sean, California on Monday, December 02, 2013

Crutchfield Customer Review (What's this?)

This is an amp for a motorcycle or golf cart so it should not be installed in a car. It is way to small and underpowered.

2011 HD Road Glide

Written By JodyM, Brentwood CA on Wednesday, February 20, 2013

After 2 Arc amps, both would shut down after a few minutes at high volume, I installed this amp. I have 2 Boston SR65's installed in stock location and 2 SR65's custom installed inside fairing by the fork legs. The Arc was ok but something was missing. The RF was amazing night and day sound to the Arc! I highly recommend this amp for use on a Harley! Also installed one under the seat of my Lightning to run inside 4 speakers!

Pros: Everything

Cons: Wasn't free

RF Amp

Written By JohnL, Madison, WI on Monday, November 05, 2012

Crutchfield Customer Review (What's this?)

Great little amp. Perfect for motorcycle faring mount.

Pros: Small, compact, easy install.

Dont install in a Harley Davidson Ultra Classic without reading this

Written By Tull, Union, New Jersey on Monday, September 24, 2012

Installed amp but kept over heating in a Harley Davidson Unltra Classic. Needed a special cooler to keep overheating. Contact Rockfrod Fosgate about this if you are installaing in a motorcycle.

Pros: Small size but think twice about Harley fairing installs.

Cons: prone to overheat in motorcycle fairings.

Great amp, but cannot be used with solenoid and 2nd batt!

Written By James, Brooksville, FL on Saturday, March 24, 2012

Great amp, but just a note from an installer, these amps cannot be used with a second battery and isolator relay!! Had 2 amps get fried at the shop this way, apparently the way the PBR power supply is designed, it can't take the spike that comes when the solenoid opens or closes. Had smoke come out of the amps. So if you're wiring one of these up with a big sub amp that you need a second battery for, and you're doing it the proper way and isolating it from your main battery, remember to hook this one up to the main battery, away from the solenoid!

Fits great in a Dragonfly Fairing

Written By Eric, Cottage Grove, WI on Thursday, March 22, 2012

Crutchfield Customer Review (What's this?)

What difference this small powerhouse made for my wife. She was having trouble hearing her stereo at about 70 or so on the Interstate. Just fine now! The unit was so easy to install when used in conjunction with the RF amp install kit. Highly recommend this to anyone who might need a little more "punch" for their bike!

Pros: Small size, ease of install (use 10 gauge kit), makes wife happy!

Excellent in hand

Written By gnarlycs, Detroit, MI on Saturday, March 17, 2012

One word - excellence. This tiny little amp will put out beyond your wildest dreams. There's only one catch, you need to set your gains perfectly. That's all. Once your gains are matched with your head unit perfectly (and I mean perfectly) this little amp will bring your speakers to life.

Pros: Small, powerful, boosted-rail tech, Rockford Fosgate build quality

Cons: The power puck says it's designed for 10 gauge wire, but if you buy a Rockford Fosgate amp wiring kit, do not get the 10 gauge one, get the 12 guage kit. Reason being is Rockford Fosgate likes to over-spec their wires (add more copper and less insulation) so the physical size of the wire is still 10 gauge, but the size of the actual copper is 8 gauge. This is from experience, the 10 guage Rockford Fosgate amp wiring kit is too big for the PBR300X4's power puck (molex connector).

Rockford Fosgate PBR300X4

Written By Duane, Spartanburg, sc on Thursday, March 15, 2012

Crutchfield Customer Review (What's this?)

Great kit every thing I needed! I would try to gear this product to motorcycle people!

Small amp... Tons of power!!!

Written By Devin, Kenosha WI on Friday, December 30, 2011

Amazing amp. Totally worth the price. I got a scratch and dent and i didnt see any scratches or dents. This amp is so small that you could tuck it in the smallest places. Under the seat of a car ect. 4 lbs for an amp is tiny. Its like holding a super baby. This amp is small, light and looks "cute" but its going to blow you away when you hook it up and turn up that volume. I just barely got a tease. Cant wait to get the whole taste.

Pros: For one this amp weighs about 4 lbs. The thing is tiny. I hooked this bad boy up to my alpine 6x9 type r's in my rear deck. WOW did those speakers come to life. Bass is super responsive, the crack of the snare is awesome and the clarity is just outrageous. Birth sheet says 86 watts x 4. I got 11 more watts per channel then what i paid for it. Cant wait to hook up my front door speakers. Sadly those are cheap coustic 6 1/4. But they were free.

Cons: NONE. Just that i never worked with an amp like this so it was a learning experience.


Written By Hwork, Illinois on Thursday, October 20, 2011

Crutchfield Customer Review (What's this?)

I decided to try this amp out to replace a 2 channel amp that I was running in the fairing of my HD Street Glide. The amp I was using was "rated" at 125 watts/channel. This little RF is outperforming the bigger 2 channel on every level. The birth sheet says 85 watts/channel but it is by far cleaner and able to get louder than my last. If you are looking for an amp for your bike go no further. And Scooter was amazing with the many questions I had and saved me on shipping because I needed the amp quickly.

Pros: Ease of install, size

Cons: 8 Guage wire was a little tough to use for the power and ground.


Written By ET, Hayward, CA on Monday, September 26, 2011

Crutchfield Customer Review (What's this?)

I replaced my stock amp under passenger seat on my 1991 Porsche Carrera! Perfect size. Small enough to fit under seat but has power for my speakers! Great replacement for stock amp.

Perfect for my Harley Road King application.

Written By HessJr., Livermore, CA on Tuesday, August 23, 2011

This amp was quite impressive and was exactly what I had been waiting for. So here is my setup/story. Recently I purchased the Boom audio (windshield mount) and was only mildly satisfied. I planned on upgrading the whole system anyway so I installed some Harley CVO Speaker inserts into my Lower Fairings. I then purchased Polk Audio DXi 3.5" and 6.5" speakers. I used the 3.5s to replace the weak (30W max) "boom" audio speakers and put the 6.5s in to the lower fairings. Now the boom audio system wasn't a total loss, because it had a nicely integrated volume/power controls that mounted on the handlebars. This worked nicely with the RF Punch amps ability to sense input to power on the amp. I was also able to use the 2-channel output from the stock boom audio amp (similar to a headunit in power) and ran the wires to this amp which installed cleanly under the right side panel, next to the battery. This amp was capable of taking this 2-channel input and outputing a more than adequate 4-channel signal. I can now run down the road at 70+mph, with a short CVO style windshield and hear my music just fine (mostly rock, blues, and country). Bass wasn't an objective for my system. However I am sure a couple of Kicker 6.5 subs would fit that bill. Anyway, the amp gain is turned almost completely down and far more capable than my application, but it does the job superbly and I am simply stoked with the results. Thanks to RF and Crutchfield for bringing a product like this to the market.

Awesome power and quality

Written By Steven, Bozeman, MT on Sunday, August 07, 2011

Crutchfield Customer Review (What's this?)

Pros: VERY small, you can look at the specs and think "wow that's small" but until you actually have it in your hand you don't realize just how small it is, it's about the height and width of a VHS tape but shorter. In typical Rockford tradition it comes with a birth sheet showing actual power output of your amp. Mine said 349W RMS and 1,019 peak. It replaced an old Sony 4 channel amp which took up the entire space under my passenger seat to produce ~240W RMS for my 4 6.5s and they love the new power. The Sony sounded good but this sounds so much clearer and the extra power from the Boosted Rail technology really does help, my speakers have never actually had bass before. All of the hook-ups use little Molex connectors that are easy to install and remove, a big plus on an amp this small. Another very handy feature is the ability to take a 2 channel input and split it out to all 4 speakers, great for people that are running subs off the rear output of a 4 output deck.

Cons: Power input connector looks to be made for 10 or 12 AWG wire, my 8 AWG took some work to make it fit. Limited to 4 ohms per channel.

Overall an exceptional amp that you can mount almost anywhere, sounds excellent, puts out awesome power, and has so far lived up to Rockford's typical durability as well. If you are looking for an amp for your door speakers, this is the one!

Awesome so far

Written By Anonymous, St Pete FL on Saturday, July 23, 2011

Crutchfield Customer Review (What's this?)

This tiny amp packs quite a punch. Hard to believe so much power comes from such a tiny product. Runs Pretty hot though!!. Rocking 4 Kicker 6 1/2's and they like the power.

Great amp!!!

Written By Steve, Winterset, Iowa on Thursday, July 14, 2011

Crutchfield Customer Review (What's this?)

I have this amp on a 2009 Road glide running four 6 1/2 polk audio speakers and it sounds great. I believe this amp is better than any other on the market, especially for motorcycles. It fits perfectly above the stock or aftermarket stereo in the fairing of a Harley Davidson shark nose or batwing.

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Two 7" Speaker output harnesses (Molex plug on one end and tinned bare wire on the other)
  • Two 12" Input harness (Molex plug on one end and female stereo RCA jacks on the other)
  • Installation & Operation manual (English/ French/ Spanish/ German/ Italian)
  • Amplifier Performance Verification Certificate

Product Research



Boosted Rail Technology: The PBR300x4 uses Boosted Rail Technology (BRT), an efficient design that doesn't use a switching power supply. The PBR300x4's average efficiency is more than 75%, meaning it doesn't generate much heat and can maintain a small footprint.

Signal Input: The PBR300x4 is compatible with either line-level (RCA) or speaker-level inputs. The included Molex-to-RCA is used in both cases; the RCA end is cut off for connection to speaker wires.

Auto Turn-on: When using speaker-level inputs the amp will automatically turn on when it senses an input signal (4 volt minimum). The threshold voltage (DC offset) for auto turn-on is adjustable from 4 volts to 6 volts.

Dynamic Thermal Management (DTM): DTM Evenly distributes excess heat across the entire extruded aluminum heatsink.

MEHSA³: MEHSA³ (Maximum Efficiency Heat Sink Application-Third Generation) is a Rockford Fosgate proprietary process that increases the heat transfer from the MOSFET devices to the heatsink. The multi-layer insulated metal MEHSA substrate operates with minimal thermal resistance, spreading heat both downward and outward to quickly dissipate heat from each device across the heatsink. This allows greater power output, enhanced thermal stability, and maximum reliability.

NOMAD: NOMAD (NOn-Multiplying Advanced Decision) is an intelligent protection circuit that uses an analog computer to make real time decisions regarding temperature, voltage, current and impedance. The unit is protected without limiting sound output unless needed.

DSM (Discrete Surface Mount): In the manufacturing process high speed robotics are used to place 1% tolerance parts and large board traces. DSM improves the efficiency of the circuit, decreases cross-talk from other discrete components and lowers operating temperature.

LEDs: The Power/Protect LED on the right side of the amp illuminates blue when the amp is turned on and operating normally; it illuminates red when one of the protection circuits has engaged (short circuit, impedance too low, or temperature too high). The BRT LED on the left side of the amp illuminates white when the boost mode is engaged.


Crossover: The front and rear channels have independent crossover switches. Each can be set to low-pass, all-pass (crossover is bypassed), or high-pass. The crossover point is fixed at 80 Hz and the slope is 12 dB/octave.

Gain: The front and rear channels also have independent input gain controls, adjustable from 150mV to 11V.

2/4 Channel: When using only one set of inputs, set this switch to 2-channel and connect the inputs.

DC Offset: The DC offset threshold voltage for the auto turn-on circuit is adjustable from 4 volts to 6 volts (useful with speaker-level inputs).


Power Connections: The power, ground, and remote turn-on terminals are c-clamps on a removable plug. Each terminal will accommodate up to 10-gauge wire (Rockford recommends 10-gauge minimum for the power and ground wires). A flat blade screwdriver (not supplied) is required to tighten/loosen the terminals. There is no fuse on the body of the amp, so an external 30-amp fuse (not included) must be installed in the power wire. If a wiring kit is used that includes a different value fuse, the original should be replaced with a 30-amp fuse.

Signal Input: The included input harnesses have Molex plugs on one end (plugs into the amp) and female RCA plugs on the other. When using speaker-level inputs the RCA end is removed and the four individual wires are used.

Speaker Output: The included speaker output harnesses have Molex plugs on one end (plugs into the amp) and tinned bare wires on the other.

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.