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Pioneer GM-A6604

4-channel car amplifier — 60 watts RMS x 4

Item #: 130GMA6604

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7 Reviews | 5 questions - 12 answers

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Plays loud and clear

Many people never think to upgrade their car's audio system, suffering with subpar sound when they listen to music. Pioneer's GM-A6604 4-channel amplifier will greatly improve the sound quality in your vehicle, so you'll look forward to spending time on the road. This punchy Pioneer amp will power your front and rear speakers with 60 watts RMS each, which is a huge jump over the power supplied by your car radio. You'll hear more of the little details in your music, even when you turn your system up to compete with the road noise.

Practical features

You can also put this versatile amp into 2-channel mode to send up to 180 watts RMS each to a couple of component speakers or subwoofers. Switchable 80 Hz high- and low-pass filters on the A channels help take the rumble away from full-range speakers or the sizzle away from a sub. The B channels sport variable high-and low-pass filters so you can better adjust the sound for critical front soundstaging or a finely-tuned bass. A bass boost adds extra kick, if you want it. Speaker-level inputs allow you to add the GM-A6604 to a factory radio. This amp's performance features and reasonable price make it a great choice for almost any vehicle needing a sonic upgrade.

Product Highlights:

  • 4-channel car amplifier
  • 60 watts RMS x 4 at 4 ohms (90 watts RMS x 4 at 2 ohms)
  • 180 watts RMS x 2 in bridged mode (4-ohm stable in bridged mode)
  • CEA-2006 compliant
  • switchable high- and low-pass filters (80 Hz, 12 dB/octave) on A channels
  • variable high- and low-pass filters (40-500 Hz, 12 dB per octave) on B channels
  • bass boost (0-12 dB at 50 Hz) on B channels
  • MOSFET power supply
  • preamp and speaker-level inputs
  • fuse rating: 25A x 2
  • 8-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 13-3/4"W x 2-3/8"H x 8-1/2"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.

Pioneer GM-A6604 Reviews

Average Customer Review:

7 Reviews

Pioneer GM-A6604

Written by: Anonymous from New Jersey on August 8, 2015

Crutchfield Customer Review (What's this?)

Pwerfull & Clear

Pros: Better then my OME Amp, was able to mount it a place where no water damage could affect it.

Cons: Had to mount it next to my OME Sub Woffer.

Great amp

Written by: Anonymous from Olive branch, MS on July 6, 2015

Crutchfield Customer Review (What's this?)

Great amp with plenty of power and good clarity.

Pros: Good clear, crisp sound

Cons: Was too big to conceal in my car. Not a big deal though.

Very nice amp

Written by: Anonymous from Maryland on June 5, 2015

Crutchfield Customer Review (What's this?)

Purchased this to install in a 1969 Camaro, using 2 Polk rear deck speakers and a Retro sound custom dash speaker. The amp is great for this application. Being able to adjust the level for front and back speaker output, and HPF with range adjustments has been beneficial for tuning to match the speakers and car. Plenty of power, clean and clear. Would buy this item again, recommended amp.

Pros: Plenty of power for my app, great adjustability

Cons: None

Great Amp

Written by: Vanessa from Apache Junction, AZ on April 11, 2015

Crutchfield Customer Review (What's this?)

It is a very got amp, decent size and fits perfect under my car seat



Great Amp

Written by: 415reviews from Ross, CA on January 29, 2015

Crutchfield Customer Review (What's this?)

I needed a great amplifier that could handle some pioneer d series speakers I had purchased. I was suggested this amplifier and at such a great price I couldn't refuse. I have been using it now for a month and have had no problems. It's a great amplifier that runs notable power for such a low price.

Pros: Price was low Easy to wire 4 channel, including bridged mode Numerous ports for any wiring variation Great power

Cons: None so far

Perfect upgrade to factory system

Written by: CCO from Atlanta, GA on October 28, 2014

Crutchfield Customer Review (What's this?)

Love it made a crappy Toyota factory radio sound like an expensive aftermarket radio

Pros: Easy installation,

Cons: Wish it was more of a square shape so I could have mounted it under the seat


Written by: toppnoff from SF, California on August 25, 2014

Crutchfield Customer Review (What's this?)

Awesome amp! I paired this amp up with four Pioneer TS-A6885R 3way door speakers. This 4 channel amp transformed my F-250 to a great joy rider. Easy hook up, power adjustments, just solid all the way around! Thank you pioneer for the outstanding equipment!

Pros: Easy hook up, more than adequate power.

Cons: None

Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Two 25amp ATO fuses (installed)
  • 4" Speaker-level input harness
  • Four 5/8" Self-tapping screws
  • Owner's Manual (English/ French/ Spanish)
  • Warranty information

Product Research


CEA-2006 Compliant: CEA-2006 is a system of testing and measurement methods for mobile audio amplifiers. This voluntary standard advocates a uniform method for measuring an amplifier's RMS power output and signal-to-noise ratio. The criteria for measuring power uses a DC input voltage of 14.4 volts and the RMS power output is measured into a 4Ω load, with 1% or less Total Harmonic Distortion plus noise (THD+N), and over a frequency range of 20 Hz to 20 kHz (for full range amplifiers). Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4Ω. CEA-2006 standards allow consumers to compare amplifiers on an equal basis. Using CEA-2006 criteria, the Pioneer GM-A6604 is rated at 60 watts RMS x 4 channels, with a 78 dBA signal to noise ratio.

Specifications: The manual also lists these non CEA-2006 compliant specifications:

  • Power:
    • 2Ω: 90 watts x 4 channels (14.4 volts, 1 kHz, no more than 1% THD+N)
    • Bridged: 180 watts x 2 channels (into 4Ω, 14.4 volts, 1 kHz, no more than 1% THD+N)
  • Signal to Noise Ratio: 95 dB (at rated power)

Gain Control: The A and B halves of the four channel amp have independent gain controls. To accommodate the varying range of signal levels coming from today's factory and aftermarket radios, the input gains are adjustable (300mV-6.5V line level, 3V-26V speaker level).

Gain Control Caution: If the gain control level is set too high, Pioneer's Gain Control Caution feature will automatically reduce the amplifier's output until the headunit volume is decreased to acceptable levels. This added layer of protection helps prevent damage to the amplifier and the connected speakers due to improper gain control adjustments.

Crossovers: The A and B sections of the amplifier also have independent crossover circuits:

  • A: The A channels' crossover point is fixed at 80 Hz and the slope is 12 dB/octave. A three position switch specifies the crossover operation: LPF (low-pass), Off (crossover bypassed), or HPF (high-pass).
  • B: The B channels' crossover point is continuously variable from 40 to 500 Hz and the slope is 12 dB/octave. A three position switch specifies the crossover operation: LPF (low-pass), Off (crossover bypassed), or HPF (high-pass).

Bass Boost: The B channel outputs have a bass boost circuit, centered at 50 Hz, that is variable from 0 dB to +12 dB.

Power Connections: The power and ground connections are 0.54" wide screw terminals, the remote turn-on screw terminal is 0.325" wide. A Phillips-head or flat blade screw driver (not included) is required to tighten/loosen the terminals. Spade connectors are recommended for the power, ground, and remote wires.

Speaker Connections: The speaker screw terminals are 0.325" wide. A Phillips-head or flat blade screw driver (not included) is required to tighten/loosen the terminals. Spade connectors are recommended for the speaker wires.

RCA Input: The amplifier features two pair of stereo RCA line level inputs, left/right A and left/right B.

Input Select: When using only one pair of RCA inputs, set the Input Select switch to 2CH to send the one pair of inputs to both the A and B sections of the amp.

Speaker Input: The included four channel speaker level input harness allows you to connect your OEM radio (or aftermarket radio that does not have the typical RCA-type outputs) without having to buy an adapter.

Auto Power On: When using the speaker level input, a circuit senses the input signal and turns the amp on automatically. This feature makes it easier to add an amplifier to a factory radio.

Fuse: The amp is protected by two 25-amp ATO blade fuses.

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.

Customer Q&A

5 questions already asked

Thanks for your question. For information on selecting the best subs for your amp I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They will be able to help determine the differences between the models and help you make the best choice for your system. [ Krissy  Aug 31, 2015 ]  Staff
Thanks for your question. For information on selecting the best amp for your speakers I would recommend reaching out to an Advisor by phone (1-800-324-9695) or online chat. They will be able to help determine the differences between the amp models and help you make the best choice for your system. [ Krissy  Mar 15, 2015 ]  Staff
From a sound standpoint there should be no difference. Using the signal input harness as I did required running 4 pair from the radio to the amp whereas the RCA version would avoid that but would require the power/signal wire to be run. Hindsight I probably would've went with the RCA version to avoid pulling those extra wires. I am very pleased with the amp. [ Thomas  Oct 04, 2014 ]
Sir, not sure if there would be a difference. I chose to use RCA inputs and it has been so clean sounding, I was amazed how perfect this amp paired up to my door speakers. [ JONATHAN  Sep 30, 2014 ]
I have not installed it yet. [ LAURENS  Sep 29, 2014 ]
RCA - for two reason.. 1.2 wires vs four wire to run 2.The RCA signal wires are shielded [ DAVID  Sep 29, 2014 ]
The best is the low level input (RCA ) this is the non amplified output from the source. It is controlled level output with little to no distortion. The high level input (speaker level) is the amplified output of the source. And this can be to high and distorted depending on volume level from source. [ mike  Sep 29, 2014 ]
The Pioneer 6604 can be run on 3 channels. A side at 60w RMS in stereo and the B side run at 180w RMS in mono. [ Ronald  Jul 10, 2014 ]
This amp bridges at 180x2 but trying to make it a 3 channel may spell failure. [ Evan  Jul 08, 2014 ]
You'd probably be better off with a 2 channel amp for the 6.5's and a mono amp for the sub. It is possible to bridge channels 1&2 and 3&4 together to make 2 channels, but not sure if it will work they way you are asking. Besides this amp is only about 60 rms per channel giving you only 120 rms to a sub even if it did work. Also your ohm rating may be off and blow the amp [ Evan  Jul 08, 2014 ]
The box the 6604 came in says, 4ch-3ch or 2ch. [ Ronald  Jul 08, 2014 ]