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Rockford Fosgate PBR300X4

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

Item # 575PBR3004

You won't believe how small and powerful this amp is.

Find what Fits your vehicle

You won't believe how small and powerful this amp is.

Discontinued item
3 questions - 5 answers

Item # 575PBR3004

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About the Rockford Fosgate PBR300X4

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.

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
  • suitable for powersports application
  • 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
  • MFR # PBR300X4

What's in the box:

  • 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

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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.

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Customer Q&A

3 questions already asked

What wired marine remote would be compatible with this amp?
[ Chris  May 11, 2017 ]
1 answer
You can use the Rockford Fosgate PLC-U universal remote with the PBR300X4 amp: If you would like to discuss further, please contact an Advisor directly by phone (1-800-324-9695) or online chat.
[ Larry  May 16, 2017 ]  Staff
If i run 2 of these amps on my Harley will that be to much for my lithium battery to run?
[ jonmote  Sep 02, 2015 ]
1 answer
It would clearly depend on the capacity of the battery. Each amp is supposed to be fused with a 30A fuse, so having a battery capable of 60A output for an extended period is one way to look at it. The amps are rated at 300W each, so 600W of output with a 12V source would require 50A, and the amps are said to be about 85% efficient; so mean about 59A of input to get that output. If you are not pushing the amps to full capacity, then it would obviously require less power. So if your battery is rated at 60Ahr, then it would supply the 60A for one hour. I have no idea what the actual capacity of the Harley battery would be though.
[ Scott  Sep 03, 2015 ]
Thinking about running the pbr300x4 on my Harley, with the switch on 4ch. do I need 4 speakers hooked up all the time or can I unplug the 2 in my tour pac and still use it that way and not harm the amp? Thank you, Eric
[ Eric  Jun 22, 2015 ]
3 answers
You will be fine running that way, I am running in a similar fashion but with 6 speakers. You can anyways switch between 2/4 channels if you want. Just make sure you get good speakers don't chince on them
[ Daniel  Jun 22, 2015 ]
Yes you can unplug the tour pack one thing though I been on two trips on 100 plus days and the amp trips out high heat. mounted in faring I have added a fan to help cool it down have not tried it yet but I think the fan will take care of the issue other wise great amp
[ TIM  Jun 22, 2015 ]
I have not tried that specifically, but running an amp with no speaker load on 2 of the 4 channels should not hurt the amp. It is usually a short circuit that is drawing excessive current that burns up the output transistors.
[ Scott  Jun 22, 2015 ]

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