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4-channel car amplifier — 60 watts RMS x 4

12 Reviews | 3 questions - 5 answers

Item # 109GXA604

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Our take on the JBL GX-A604

JBL has been designing and building sound systems for decades, so they know a thing or two about power. Their GX-A604 4-channel amplifier can send 60 watts RMS to each of your front and rear speakers, about five times the power of most factory radios. The GX-A604 includes speaker-level inputs, so it's perfect for upgrading the power in a factory system. 

Power for clarity

JBL has been designing and building sound systems for decades, so they know a thing or two about power. Their GX-A604 4-channel amplifier can send 60 watts RMS to each of your front and rear speakers, about five times the power of most factory radios. The GX-A604 includes speaker-level inputs, so it's perfect for upgrading the power in a factory system. 

Versatile tone filters — versatile amp

You can also use the GX-A604 in 3-channel mode, using the front channels to power your front speakers, and bridging the rear channels together to drive a subwoofer with 170 watts RMS. A high-pass filter cleans up the sound by removing extreme low bass from small full-range speakers, allowing them to play louder and cleaner. You can switch the rear filter to low-pass mode when you're driving a subwoofer, while the built-in bass boost adds some punch when you're in the mood.

Product Highlights:

  • 4-channel car amplifier
  • 60 watts RMS x 4 at 4 ohms (85 watts RMS x 4 at 2 ohms)
  • 170 watts RMS x 2 at 4 ohms in bridged mode (4-ohm stable in bridged mode)
  • switchable high-pass filters (80 Hz, 12 dB/octave) on front channels
  • variable high- and low-pass filters (32-320 Hz, 12 dB per octave) on rear channels
  • switchable bass boost (0, 12 dB at 45 Hz) on rear channels
  • preamp and speaker-level inputs
  • fuse rating: 20A x 2
  • 8-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 11-13/16"W x 2-1/16"H x 8-1/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee

What's in the Box:

  • 4-Channel amplifier with two 20A ATO fuses installed
  • Two 8.25" Speaker-level input harnesses
  • 4 Self-tapping screws (Length=3/4")
  • Owner's Manual

I really like this amp and would recommend it to anyone. Easy to install easy to tune

tph, tampa, FL


JBL GX-A604 Reviews

Average Customer Review(s):

(12 Reviews)
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Hands-on research

Product Research



Power Output: The JBL GX-A604 Class AB 4-channel amplifier delivers the following power output (RMS Power Output @ 1% THD+N, 14.4 VDC):

  • 60 watts x 4 @ 4 ohms
  • 85 watts x 4 @ 2 ohms
  • 170 watts x 2 bridged into 4 ohms

Protection Circuitry: The amplifier features protection circuitry for thermal overload, over- or under-voltage (<9V or >16V), and short circuits. The LED on the end of the amp glows red if the amp goes into protection mode.


Input Level: The GX-A604's rotary gain control let you match the amp's input sensitivity to the output of the source unit. There are independent input level controls for the front and rear channels. The input sensitivity range of the amplifier is continuously variable between 200mV and 12V. A small screwdriver (not included) is required to set the gain.

Input Mode: The amp's 4 channels can be driven by input signals from 4 channels. If you only have 2 channels of input, the Input Mode can be switched to "2CH" and all four channels will receive audio signal from the two connected inputs. The switch should remain at "4CH" if there are 4 inputs connected.

Crossover: The amp features separate crossovers for the front and rear channels. For the front, there is a selectable 80Hz high-pass filter with an On/Off switch. The rear channels feature a 32Hz to 320Hz variable crossover. A 3-way switch lets you configure the crossover for high-pass or low-pass operation, or switched to "flat" to defeat the crossover.

Bass Boost: The GX-A604 has a switchable 12dB bass boost, centered at 45Hz, for the rear channels. This is useful when using the rear channels of the amplifier in bridged mode to power a subwoofer.


Terminals: The JBL GX-A604 uses screw terminals for the +12V power, ground, turn-on (remote) lead, and speaker outputs. The screws can be tightened/loosened with a Phillips-head or flat-head screwdriver (not provided).

Power/Ground: The +12V Power and Ground terminals will accept spade connectors up to 1/2" wide. It is recommended that you use an 8 AWG power wire to the battery, with an in-line 50A fuse installed no more than 18" from the battery terminal. An 8 AWG ground wire (minimum) should be used, and attached to a metal area close to the amplifier.

Remote Turn-On: The Remote screw terminal will accept a spade connector up to 3/8" wide. Typically, an 18 AWG turn-on lead is included in an amplifier wiring kit.

Speaker-Level Input: The amp includes two Speaker Level Input harnesses for connecting the amp to a factory radio or aftermarket head unit without preamp outputs. You should splice left and right speaker wires from the head unit to each harness and plug the harnesses into the amp.

Line-Level Inputs: The amplifier is equipped with two pairs of RCA inputs for connecting stereo RCA patch cables from the head unit to the amp. If you are bridging the amplifier's rear channels and have only one input for the rear channel, a "Y"-adapter will be needed to connect the left and right rear RCA inputs.

Speaker Outputs: The amp features screw terminals for connecting speakers in 4-channel, 3-channel, or 2-channel configurations. In 3-channel mode, the front channels are connected in stereo and the rear channels are bridged (using Left + and the Right - terminals). For 2-channel mode, both pairs of speaker terminals are bridged. The terminals will accept a spade connector up to 3/8" wide.

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Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Jackson helped me out with this. As I could not really afford at this time to get the ultimate package I really wanted. I decided just to get something to tide me over until I can pull out the stops and get the set up I want. I'm sure this will do the job for now. Plus I found a scratch & dent model (who is going to see it anyway?) and found some rewards points that I applied......perfect !!! Jackson's Bio: [ M  Apr 17, 2016 ]
this was recommended by my advisor as a good fit for the stereo I purchased [ steven  Mar 13, 2016 ]
to match aftermarket door speakers [ CHRIS  Mar 04, 2016 ]
Quality and fit [ William  Feb 28, 2016 ]
A lot of positive reviews on this item. [ CHARLES  Jan 21, 2016 ]
After much research and speaking with advisors, I finally came across this amp. It does everything I need, all packed within a quality brand. Someone once told me that it's okay to buy cheap stuff for things that don't matter as much, but with electronics, especially car audio, you never buy cheap. [ ANDREW C  Dec 24, 2015 ]
Advisor Larry recommended this amp. [ ERIC M  Dec 05, 2015 ]

3 questions already asked

When powering those 2.3-ohm JBL/Infinity speakers with an external amplifier, you can expect your amp to provide roughly the same wattage output at 2-ohm as you would at 2.3-ohm. So with this amp for example, you would get approximately 85 watts RMS x4 when powering the 2.3-ohm speakers. [ Larry  Nov 27, 2015 ]  Staff
I believe tri-mode [ Jeremy  Sep 02, 2015 ]
Yes, this amp can run iin 3-channel mode - the front channels are connected in stereo and the rear channels are bridged (using Left + and the Right - terminals). [ Jeff  Aug 31, 2015 ]  Staff
I mounted the amp under the driver's seat directly to the carpet using only the hook portion of 2" strips of self adhesive Velcro attached to the bottom of the amp since it didn't want to drill any holes into the floor of the vehicle for screws. I had the amp oriented such that the terminal blocks were facing towards the center console for easier input/output wiring. I put a 2" slice in the carpet next to the center console to pass the wires to the head unit, speakers and battery. The cut in the carpet was placed low enough so that you couldn't see it after the seat was reinstalled. This Velcro mounting system also allowed me to make minor adjustments to the amp's position under the seat for the best placement so the amp would not get kicked by a passenger in the back seat or get caught by any seat parts when the driver adjusted the seat forward and back. Hope this helps. [ FRED  Apr 02, 2015 ]
Hi, I mounted it in the trunk, on a piece of board. The board is attached to the metal frame that backs up the rear seat. So it is in a vertical position. the car is a Nissan Maxima. Hope this helps. [ William  Mar 30, 2015 ]

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