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Pioneer GM-A4604

4-channel car amplifier — 40 watts RMS x 4

Item #: 130GMA4604

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9 Reviews | 3 questions - 4 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-A4604 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 40 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 120 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. Speaker-level inputs allow you to add the GM-A4604 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
  • 40 watts RMS x 4 at 4 ohms (60 watts RMS x 4 at 2 ohms)
  • 120 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
  • Class AB amp technology, MOSFET power supply
  • preamp and speaker-level inputs
  • fuse rating: 30A x 1
  • 8-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 13"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-A4604 Reviews

Average Customer Review:

9 Reviews

Good 4 channel

Written by: Dakota from minot, ND on February 1, 2016

Crutchfield Customer Review (What's this?)

Great amp as far as clean sound and powerful delivery



Pioneer amplifier

Written by: Johnny F from Puerto rico on September 1, 2015

Crutchfield Customer Review (What's this?)

Excellent quality better price

Pros: Small ,appropriate output and good quality


Sounds great

Written by: harold from Texas on June 12, 2015

Crutchfield Customer Review (What's this?)

Installed this amp in a 2010 Mazda 5 with the factory GPS head unit. Paired it with 2 pair of Pioneer TS-A6885R speakers. It sounds nice, crisp and clean. Really happy with this amp and the speakers.

Pros: Speaker level inputs, perfect match for a factory unit and 2 pair of speakers.

Cons: None

Pioneer GM-A4604

Written by: Tom M. from Maryland on May 12, 2015

Crutchfield Customer Review (What's this?)

Easy to install. Great sound....really helped out my system.

Pros: Good directions...great tech support.

Cons: Unit was a tight fit under seat.

Pioneer GM-A4604

Written by: John B. from Mississippi on April 13, 2015

Crutchfield Customer Review (What's this?)

Just installed a Pioneer GM-A4604 4-channel amp in my friends car and it sounds great. Plenty of power and punch now!

Pros: Sounds and Looks Great...

Cons: None

Pioneer GM A-4604

Written by: TC from Nevada on December 16, 2014

Crutchfield Customer Review (What's this?)

sounds great, runs 4 6x8 speakers with power to spare. I give it a 5 star rating

Pros: Good price, great quality

Cons: none

Great Amp

Written by: Pioneer 4604 from PA Philadelphia on September 1, 2014

Crutchfield Customer Review (What's this?)

Great sounding Amp well worth the money sounds great clear sound

Pros: Good brand

Cons: None

Amplifier Review

Written by: Ron from Chestertown, MD on March 29, 2014

Crutchfield Customer Review (What's this?)

Got this amp to power 4 replacement 5X8 speakers. Great stock upgrade.

Pros: Powers multiple channels


Pioneer GM-A4604

Written by: Anonymous from M'boro on January 13, 2014

Crutchfield Customer Review (What's this?)

Wonderful amp to run full range speaker,...

Pros: Great sound for the price


Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • 30amp ATO fuse (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-A4604 is rated at 40 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: 60 watts x 4 channels (14.4 volts, 1 kHz, no more than 1% THD+N)
    • Bridged: 120 watts x 2 channels (into 4Ω, 14.4 volts, 1 kHz, no more than 1% THD+N)
  • Signal to Noise Ratio: 94 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).

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.

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.

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.

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 or to a receiver with no preamp outputs.

Fuse: The amp is protected by a single 30-amp ATO blade fuse.

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

3 questions already asked

yes it definitely is. With this amp I never have to turn my head unit past 14 out of 35. and thats with all 4 windows down [ AUSTIN T  Jul 20, 2015 ]
Thanks for your question. For information on selecting the best amp for your subs and 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. [ Greg  Jul 20, 2015 ]  Staff
Thanks for your question Hiram. You'll be happy to know that you can certainly run the amp this way. It is a great solution for many systems. [ Jeff  Dec 16, 2013 ]  Staff