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Infinity's Reference Series amplifiers offer impressive power and extensive controls for fine-tuning your sound — an ideal way to boost your music's intensity and clarity. Strict reliability testing results in durable, dependable amplifiers, and their compact size gives you more installation options in tight places.

The heavy-hitting Infinity Reference 475a 4-channel amplifier sends 75 watts RMS to each of your front and rear speakers. Or, you can bridge the amp to 2-channel mode, and pump out 360 watts total to your two subs. And every Infinity Reference amplifier is certified to deliver power as advertised.

The variable frequency filters and adjustable bass boost let you contour the amp's output to suit your speakers or subs for more efficient output and cleaner low-end kick. Preamp outputs simplify hookup to another amp in your system, so system building is quick and easy. Direct-connect terminals make reliable connections without need for any crimping or soldering.

Product Highlights:

  • 4-channel car amplifier
  • 75 watts RMS x 4 at 4 ohms (90 watts RMS x 4 at 2 ohms)
  • 180 watts RMS x 2 at 4 ohms in bridged mode
  • CEA-2006 compliant
  • variable high- and low-pass filters (32-320 Hz, 12 dB/octave)
  • variable bass boost (0-6 dB at 50 Hz)
  • Class-AB amplifier design
  • MOSFET power supply
  • preamp-level inputs and outputs
  • fuse rating: 35A x 2
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 14-3/4"W x 2-11/16"H x 9"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.

Infinity Reference 475a Reviews

Average Customer Review:

27 Reviews

Trash in less than 6 months

Written by: John B. from Overland Park, KS on February 28, 2015

Crutchfield Customer Review (What's this?)

Amp was installed along with Infinity speakers, Infinity BassLink, and Kenwood head unit by professional shop. All equipment purchased from Crutchfield. Less than 4 months after install, amp stuck in Protect mode and utterly useless. Glad to see it's discontinued. Speakers and other equipment still work well. Infinity amps, at the very least, should be avoided. Laughably, Infinity will assess $15 restocking fee for lack of original packaging. If you take the plunge, make sure you have ample warehouse space available to maintain all boxes, etc.

At least Crutchfield service is more consumer-minded than the dopes at Infinity, and proactively processed an equipment exchange.

The one star rating was earned by Infinity, whereas Crutchfield gets an A.

Pros: If used as a paperweight, paperwork will surely be secure. Also, worked as an amplifier spectacularly...for only four months and change.

Cons: Died after less than 5 months. Junk. Will avoid entire Infinity line as a result of this defective unit.

Rocks my Jeep!

Written by: Jim from Colorado on November 9, 2014

Crutchfield Customer Review (What's this?)

Great sounding Amp; Make sure you have room to install, the amp is a large amp and it requires lots of airflow to keep it cool. I have it on a Kenwood eXcelon 997 deck, Infinity speakers (frnt and rear) and a JL 8 sub with its own amp. HairNation never sounded so GOOD!

Pros: Easy to install and setup

Cons: Large Size

Very pleased!

Written by: Joe S. from Statesville, NC on November 1, 2014

Crutchfield Customer Review (What's this?)

This was a great purchase! And with Crutchfield's prices it didn't hurt my wallet either. Crutchfield is great customer service and great products!

Pros: Great price, great sound, and looks sleek.

Cons: A little heavy

Infinity Reference 475a

Written by: Anonymous from pa on October 17, 2014

Crutchfield Customer Review (What's this?)

Got this amp to run pair of kicker cs components in front door and kicker cs 6.75 in rear door amp works great run gain all the on down on full range sounds great don't run hot and for the price can't beat it had in for lil over a month now. And it hooked up to factory 14 tacoma Hradec run in to tacotunes recurve sounds fantastic



very nice

Written by: ron from fort wayne, in on July 22, 2014

Crutchfield Customer Review (What's this?)

used it in my 88 trans am and it looks and works perfectly for the 4x6 fronts and 6x9 rears

Pros: very easy to tune, nice looking unit that is easy to custom fit

Cons: none so far

infinity amp

Written by: gus from Yuba City, CA on July 6, 2014

Crutchfield Customer Review (What's this?)

Great amp for price

Pros: Good amp

Cons: None

Great Amp!

Written by: EROK14R from Renton, WA on June 30, 2014

Crutchfield Customer Review (What's this?)

This is a fantastic amplifier! So much clean power! I've got it hooked up to a Pioneer deck with 4V pre-outs. My speakers are Polk DB 5.25 components. I have the amp gain only at 25% and the speakers get killer loud and retain crisp sound clarity. I got this amp when it was on sale, so I could not ask for more for the price.

Pros: Powerful, clean, affordable

Cons: It's an older model amp and with that comes a larger size. I had plenty of room, so this wasn't an issue for me, but if you have a small mounting space you should consider looking at newer more compact amps.


Written by: Mike T. from New york on January 28, 2014

Crutchfield Customer Review (What's this?)

I kept my stock head unit since it has an excellent tuner in it. One of my original speakers was blown. However adding this amplifier to a complete set of 4 6.5" Infinity reference component speakers has created fantastic sounds in my Avalanche. The Infinity speakers are rated to handle 90 rms peak and the unit puts out 75 rms so it's as perfect as you'll get. The clarity, as well as bass and highs is excellent. Thank you Crutchfield for a great price on a great product.



Runs HOT. Does not last long.

Written by: Anthony from Philadelphia,Pa on August 23, 2013

Crutchfield Customer Review (What's this?)

Purchased this amp with the advice from a sales associate. It runs hot so have it in an open area. I was only able to get 2 1/2 years out of it tops before issues. It went into protect mode on and off. I called to see what it could be I was advised that its probably the speakers. So I purchased all new speakers. Wasn't the speakers it was the Amp.. I have an old Sony amp pushing my sub that's way over 15yrs old and it still works. So maybe $100 per year is what's expected.

Pros: Produces good sharp sound

Cons: Can not depend on it working. Check reviews elsewhere. Lots of issues .

Great Amp

Written by: CReed from Covington, LA on July 8, 2013

Crutchfield Customer Review (What's this?)

THIS AMP ROCKS. 5 Channels, so I hooked a component set (6 1/2 door & Tweets) + Rear (Infinity 6 1/4) and the 5th channel I hooked a tear shaped box with 4 POLK 6x9 Woofers in it. All sounds exactly how I imagined... but better



Infinity 475a - a solid choice

Written by: Daniel from Atlanta, GA on June 21, 2013

A very solid amplifier with good sound quality, and plenty of power. It pushes my polk db 6.5" component's and infinity 6x9's to their limits. I've had the 475a for 4 years now! This is the only amplifier I've had to not quit on me (mostly class D subwoofer amp's like the alpine mrp-350, mrp-1000; great amps, but gave out...). For me, the volume is at it's limit, or else I'm not listening to music haha. The Infinity 475a should be on anyone's list if they are looking for a cheaper alternative that will last, all the while sounding great!

Pros: great sound for the price

Cons: definitely runs hot - but who cares if it lasts?

bang for your buck

Written by: hoff33 from columbus ohio on April 11, 2012

I recently purchased this amplifier to replace my kicker zx650·4. I expected a considerable decrease in sound quality. But I think this amplifier sounds just as good for half the price...very nice amp.

Pros: clean crisp sound

Cons: amp runs hot

Infinity Reference 475a

Written by: Brian from Terre Haute IN on January 29, 2012

Crutchfield Customer Review (What's this?)

I purchased this for my son's 96 Ford Contour with 4 6x8 Kenwood speakers in the doors. We had previously installed a Kenwood headunit and b4 the amp it sounded pretty good. After installation I was absolutely blown away! I couldn't have imagined how good this small system was going to sound. Highs are clear and loud and the bass is difficult to believe unless you hear it firsthand. My 17 yr old son decided to not install a sub! It's only been running 3 weeks but no problems whatsoever and astounding performance.

Pros: Looks great and sounds even better

Cons: None so far

Good sound, bad quality

Written by: rnd from Boston, MA on April 20, 2010

I had this mounted in the trunk with lots of open space around it for a cool air supply. Never abused, this amp lasted 7 months when the front right channel went out (same as another reviewer here...). It performed well up until then. I have always thought Infinity's products were very good for their price point. This one was a disappointment.

Will it last? It's a gamble.



Great Amp

Written by: Sam from Diego CA on September 6, 2009

Crutchfield Customer Review (What's this?)

I bought this amp to power my Infinity referance 5030 and 5032 it rocks those speakers!! my music is loud and clear love infinity. My father said they where some of the best and he was right.
Really loud and clear
I have alot of Static through them and a hummm
Have been trouble shooting and i think i got it



Best customer service on difficult sale

Written by: Rix from Charlottesville, VA on August 19, 2009

Crutchfield Customer Review (What's this?)

The quality of customer service is not measured during the smooth sales nearly as much as it is with the difficult sales. I bought this amp from Norm, who had sold me other equip. I was going to get Crutchfield to install. Upon review by the installer, Devon, he found that he was going to have to do some extensive electrical surgery that was not in Crutchfield's database. I appreciated explanation, and return of the amp was cheerfully accommodated. I was impressed with the trouble Norm & Devon went to try to figure an easy way to make the install work, but, in the end, it wasn't worth the tradeoffs I would have had to make. Thanks, guys, and I will definitely buy from you again!



Clear and powerful

Written by: Anthony from Chicago, IL on April 28, 2009

Crutchfield Customer Review (What's this?)

Just got say this amp is awesome. It's powers my 6.5" component polk audio dbs very clearly. I can turn it up real loud without distortion. This is my first amp i bought. Never thought my car would sound so much clearer and that loud.

Pros: Dirt cheap 75wx4 at 4 ohms. I probably can turn it all the way, but don't want to blow out my ears. Also its alot smaller than my sub amp. it's heavy, but looks nice and built to last.

Cons: People say it gets hot, it does, but it never shuts down on me. I don't know, but i had to switch around the patch cables a little. I dont know which one was that fault the radio or amp. No biggie Crutchfield helped me out.

I would reccomend it to my friends and family.

Also I want to say to Crutchfield. Thank you for helping me out with my purchase. You guys are the best.



Going the Distance...

Written by: Chip from Gulf Coast on April 14, 2009

Crutchfield Customer Review (What's this?)

Installed in a 2004 Jeep Rubicon, with a soft top, an audiophiles nightmare, but...BUT, this amp has made the inside of this jeep more like an amphitheater. Great purchase, excellent reco by Stephen, and an A+++ for the overall experience.



Hot amp..literally

Written by: enduroracer1970 from Knoxville Tn on February 27, 2009

Crutchfield Customer Review (What's this?)

Great amp but gets very hot. Good sound and have had it 2 years, no problems at all.



Keep Looking

Written by: sean from Raleigh NC on January 16, 2009

Crutchfield Customer Review (What's this?)

I got the fist amp and right before the year warr. went out it blew sent it to infinity and it was a nightmare they said they were going to replace it with a new amp. and i waited and waited and waited it took 8 weeks to get the amp. you can not talk to a person at infinity unless you want to buy now i got the new amp. and the front right channle is gone....I have alpine, Boston Ac.,and have never had this many problems.



You get more than you pay for

Written by: quisp from Los Angeles, CA on October 18, 2008

I got this amp to go with a set of Kappa 62.9i's. I got it figuring that I should probably amp up the 4 main 6.5" speakers if I am going to put in a 500 watt sub. I have to say that the output is pretty impressive and I would not be surprised if it was slightly higher than 90 watts/channel. The ampere rating on this amplifier is 70 amps max and it does get quite hot, but it sounds amazing none-the-less. This is is much better than it's price would indicate less than half of what I got the JL 500/1 for and is a much more important part of my system as a whole. BUY this AMP



Awesome Amp

Written by: Kyle from Malone, New York on October 10, 2008

I bought this amp to go with a set of infinity kappa 50.7cs component speakers and a set of infinity kappa 693.7i 6x9s. This amp combined with the inifinity speakers puts out very crisp highs and great mids. I can't say much for the lows, due to the fact that the speakers have crossovers that cut off much of the low-end audio; which is good as long as you have a sub. What the speakers do put out for lows is absolutely crisp up to the highest levels. Mine also tends to get very hot, so hot in some cases that I can't keep my hand on it, but it keeps on pumping out the volume, and doesn't seem to affect performance. I'm absolutely satisfied with this amp, especially for the price. I'm giving it four stars out of five only because the trim piece that you have to take off to mount the amp would not stay on for me, so I ended up taking it completely off. Probably due to the fact that I have it mounted right next to a subwoofer on the seat back of my Buick, but still it shouldn't vibrate off. Regardless of the trim falling off, I would not hesitate to buy this amp or any Infinity speaker!!



Infinity Reference 475a

Written by: no from Deerfield Beach, FL on February 19, 2008

Crutchfield Customer Review (What's this?)

Awesome ;)



Infinity Reference 475a

Written by: Kyle from Portland, ME / Manchester, NH on December 15, 2007

Bought the Infinity Reference 475a to go along with the Kappa 60.7cs and Kappa 693.7 (90 Watts to each) and I am very Impressed with the clarity and volume of the speakers and the job the amp is doing powering them. I listen to my music pretty loud and I really only use about 50% of the power this system is capable of putting out, maybe 60% if I'm feeling brave. The Highs sound awesome, the mids sound awesome and the lows are reasonable as well (if you crave bass you'll need a woofer regardless) but the lows do sound good. I really cant say anything bad about this... Mine does get very hot though... anyone else experience this? I know there is good air circulation the way it is mounted and the space in my trunk...



Awesome Amp

Written by: Jerry from New Orleans, LA on October 23, 2007

Crutchfield Customer Review (What's this?)

I just added this amp to push 4 each PIONEER TS-A6881R. I am very impress with the power this amp supplies. The amp and speakers make a good combination to provide a loud, clear and crisp sound. The speakers scream "power". Along with a MTX 500 watt amp, 2 each Eclipse 10 in. woofers and a JVC KW-AVX800 DVD Receiver , this is a awesome sounding sound system for my 07 Ford 4-door Lariat. My only complaint is the amp was too thick to mount behind my back seat with the other amp. I had to mount it under the passenger seat, which meant re-locating my tire jack. But that was a minor obstacle easly overcome. I would definitly recommend this amp to someone.




Written by: jtisthammer from Hubert, NC on July 8, 2007

Recently installed this amp and using it to run Kappa 62.7i and a 6020 component set in a 02 Jeep Grand Cherokee and it performs superbly. Love it.




Written by: Wil from Orlando, FL on June 17, 2007

I am very happy with this amp, I just installed in my toy/tac/4dr/lb it is pushing infinity 6020 comp and kappa 62.7i they sound great. Easy to adjust, very clean, crisp and it looks cool at night. It also is a mangaible size.



Hands-on research

What's in the box?

Download owner's manual

  • 4-Channel amplifier
  • Two 35A ATO fuses (installed)
  • Instructions
  • Warranty/Product Registration card

Product Research



CEA-2006 Compliant: CEA-2006 is a new system of testing and measurement methods for mobile audio amplifiers. This voluntary standard advocates a uniform method for determining 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 4-ohm load, with 1% or less Total Harmonic Distortion (THD) plus noise, and at a frequency range of 20 Hz to 200 Hz, when applicable. Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4 ohms. CEA-2006 allows consumers to compare car amplifiers and receivers on an equal basis. The Infinity Reference 475a under CEA-2006 regulations is rated at 74 Watts RMS x 4 channels with a 85dBA signal to noise ratio.

Mosfet Power: The Reference 475a's high-output PWM Mosfet power supply ensures optimum power delivery into numerous impedances with low distortion.

Bridgeable: In addition to powering 4 full-range speakers, the Reference 4-channel amplifier can be bridged and configured in a 3-channel or 2-channel application. The amplifier is rated at 180 Watts x 2 at 4 ohm in 2-channel mode and 75 Watts x 2, 180 Watts x 1 at 4 ohm in 3-channel mode.

Line Level Inputs: The front and rear channels of the amplifier each have separate line-level RCA inputs with independent gain (Input Sensitivity) controls. The Input Sensitivity controls will accept an input signal of 100mV to 6.0 Volts. If you are using a receiver with only one pair of preamp outputs you will need to use two RCA Y-adapters. When using a Y-adapter, fader controls will be lost.

Protection Circuitry: The amp features 4-way protection, and will shut itself down in the following cases:

  • DC Output: DC voltage is detected on the amplifier output
  • Temperature: Amplifier is overheated
  • Over/Under Voltage: Voltage at the +12V (Battery) terminal is less than 8.5V or more than 16V
  • Short Circuit: Short circuit in speaker or speaker wire

Power and Protection LEDs: The amplifier features a Power and Protection LED on top of the unit. The Power LED illuminates Green when the amplifier is supplied power. The Protection LED will illuminate Red when the amplifier goes into protect-mode.


Application Selectors: There is an application selector for the front and rear channels that allow you to select which channels of the amplifier drive your front or rear speakers and what channels drive your subwoofers. There is also a stereo and mono (left or right) switch for each channel of the amplifier if you want a mono signal from either the front or rear channel.

Front and Rear Input Levels: Individual rotary controls for the front and rear channels of the amplifier used to match the level of the preamp input signal.

Crossovers: The 475a has built-in high pass and low pass crossovers for the front and rear channels. The high pass and low pass crossover's slope are 12 dB/octave and are continuously variable from 32Hz to 320Hz and can be controlled independently for the  front and rear channels. The amplifier can also be operated at full-range simultaneously for both front and rear channels.

  • Crossover Mode Switches: Individual slide switches for the front and rear channels used to select Low-Pass, High-Pass or Full-Range configuration.
  • Crossover Frequencies: Independent rotary controls for the front and rear channels to set the cutoff frequency of the Low or High Pass Filter between 32 and 320 Hz.

Bass Boost: The Bass Boost control allows you to enhance the bass output of your system at 50Hz up to 6dB independently for the front and rear channels.


Preamp Output: 1 pair of gold-plated RCA jacks (amp provides a non-filtered signal for daisy-chaining additional amplifiers).

Preamp Input: 2 pair of gold-plated RCA jacks.

IMS Input: This port is designed for future Infinity expansion products.

Speaker Output: 8 Set screw terminals for connecting speaker wires; handles up to 8 gauge (16 gauge minimum recommended).


  • +12V: Set screw terminal for power wire from battery; handles up to 4 gauge wire (8 gauge minimum recommended)
  • Remote: Set screw terminal for remote turn-on lead; handles up to 8 gauge wire (18 gauge minimum recommended)
  • Ground: Set screw terminal for ground; handles up to 4 gauge wire (8 gauge minimum recommended)

Fuses: 2 Slots for 35A ATO fuses (installed)

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

1 question already asked

only 4 channel you need bridged two channel for down to 2ohms front speakers [ ANTONIO  May 11, 2014 ]
You can just run a 4 channel. I would run the 3.5" speakers directly off the head unit as it will push them just fine, and the run the door speakers off the amp! The 475a is a good amps little bulky but still works good! [ JEREL  Apr 10, 2014 ]
I think it's a good choice. 6 channel [ TAMARA  Apr 10, 2014 ]
Would be a decent choice. I've grown apart from Infinity and am not the biggest fan of their products but I still have this amp. This is my third one. Crutchfield is good about replacing them, however I have not had much luck with Infinity. A lot better than other companies like Boss and Pyle however... I would recommend Sundown Audio, Sound Qubed, or Crescendo Audio. [ BRANDON  Apr 10, 2014 ]