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Infinity Reference 475a

4-channel car amplifier
75 watts RMS x 4

28 Reviews | 3 questions - 6 answers

Item # 108R475A

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Our take on the Infinity Reference 475a

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.

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.

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!

Jim, Colorado

What's in the Box:

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

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

Infinity Reference 475a Reviews

Average Customer Review(s):

(28 Reviews)
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Hands-on research

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

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Q & A

Customer Q&A

3 questions already asked

This amp has been discontinued and we will not be able to fill an order for one or know what the current selling price of it would be. The Infinity Reference 704a amp is its replacement. You can find its information and current pricing here: My Bio: [ Paul  May 08, 2017 ]  Staff
If you purchased the product from Crutchfield, feel free to contact our Tech Support team. They can walk you through the connections on the product. Our toll-free Tech Support number is printed on your invoice, and is also available under the "My Orders" tab in the "My Account" section of our website. If you did not purchase the unit from Crutchfield, then you may want to contact the manufacturer. You can also post your question in our forums: Or try our online support center: [ Kenny  Apr 17, 2017 ]  Staff
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 ]