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Infinity Reference 704a

4-channel car amplifier — 70 watts RMS x 4

Item # 108R704A

Infinity's Reference 704a amplifier will add plenty of muscle to your music without breaking a sweat, and it'll...

Infinity's Reference 704a amplifier will add plenty of muscle to your music without breaking a sweat, and it'll...

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Discontinued item
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Item # 108R704A

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Contact our Virginia-based experts.

About the Infinity Reference 704a

Power delivered in style

Infinity's Reference 704a amplifier will add plenty of muscle to your music without breaking a sweat, and it'll look good doing it. This 4-channel powerhouse will send 70 watts RMS to each of the front and rear speakers in your car. Into planning ahead? You could use this amp in 2-channel mode now to drive a couple subwoofers with 200 watts RMS each, then reassign it to your front and rear speakers when you get a bigger sub amp.

Power delivered in style

Infinity's Reference 704a amplifier will add plenty of muscle to your music without breaking a sweat, and it'll look good doing it. This 4-channel powerhouse will send 70 watts RMS to each of the front and rear speakers in your car. Into planning ahead? You could use this amp in 2-channel mode now to drive a couple subwoofers with 200 watts RMS each, then reassign it to your front and rear speakers when you get a bigger sub amp.

Special integration features

An ADAS input lets you keep your vehicle's advanced driver assistance system's (ADAS) warning messages after you've replaced the factory receiver or amplifier. You can select which channel plays those messages, so you'll hear lane departure or blind spot warnings through your system loud and clear. And if your vehicle comes equipped with a Harman HALOsonic noise cancellation/enhancement system, you can plug it right into the Reference 704a and enjoy a super quiet or an engine-roaring ride along with your music.

Works in almost any vehicle

Speaker-level inputs allow this amplifier to work in almost any system, even if you're keeping your car's factory radio. You can use the separate high- and low-pass filters on the front and rear channels to maximize the performance of your speakers or subs.

Infinity REF-704a

Reference 704a inputs and control panel

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Product highlights:

  • 4-channel car amplifier
  • 70 watts RMS x 4 at 4 ohms (100 watts RMS x 4 at 2 ohms)
  • 200 watts RMS x 2 at 4 ohms in bridged mode (4-ohm stable in bridged mode)
  • Class D amp technology
  • variable high- and low-pass filters (32-320 Hz, 12 dB/octave) on front and rear channels
  • preamp and speaker-level inputs
  • preamp outputs
  • ADAS and HALOsonic inputs for advanced integration in select vehicles
  • fuse rating: 30A x 2
  • 8-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • 14-1/8"W x 2-1/4"H x 7-3/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee
  • MFR # Reference 704a

What's in the box:

  • 4-channel amplifier with two 30A ATO fuses installed
  • Two spare 30A ATO fuses
  • 4 Speaker wire-to-RCA adapters
  • 4 Self-tapping screws (length=2.25")
  • Quick Connect Guide
  • 2 Infinity decals

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Infinity Reference 704a reviews

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Features
Controls
Connections

Features

Power Output: The Infinity REF-704a 4-channel amplifier delivers the following power output (RMS Power Output @ <1% THD, 14.4 VDC):

  • 70 watts x 4 @ 4 ohms
  • 100 watts x 4 @ 2 ohms
  • 200 watts x 2 @ 4 ohms bridged

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

ADAS: The REF-704a has an RJ-45 interface for the Advanced Driver Assistance System (ADAS) that can override the audio source input to deliver a message or other audio from a connected ADAS accessory. On the amplifier, you can designate which speaker will output the ADAS signal.

HALOsonic: Infinity full-range amplifiers are compatible with the Harman HALOsonic noise management system found in select vehicles. HALOsonic utilizes a combination of Active Noise Cancellation and Electronic Sound Synthesis to greatly reduce engine noise and road noise in the cabin, making for a much quieter ride. The amp features a 3.5mm connection to interface with the HALOsonic system.

Controls

Gain: The REF-704a's rotary gain controls let you match the amp's input sensitivity to the output of the source unit. The input sensitivity range of the amplifier is 200mV and up. A small screwdriver (not included) is required to set the gain.

Input Level: The amp will accept low-level (line level) or high-level (speaker level) input signals. The input level switch lets you select the type of input you are using. For a high-level input, there are two settings: Hi1 and Hi2. If the audio system fails to play with an amplifier connected to its output, set the switch to the Hi2 position. The Hi2 position includes a circuit design to fool this type of factory system into "seeing" a speaker connected to its output.

Crossover: The amp features switchable crossovers that can be set to low pass (LPF), high pass (HPF), or Full Range. You can adjust the cutoff frequency of the crossover from 32Hz to 320Hz using the rotary control. There are separate crossovers for the front and rear channels.

ADAS Assign: The ADAS Assign switch is a 4-position rotary control that lets you select which speaker outputs the ADAS message: left front, left rear, right front, or right rear.

Connections

Terminals: The Infinity REF-704a uses set 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 up to 4-gauge wire. It is recommended that you use a minimum of 8 AWG power wire to the battery, with an in-line 60A fuse installed no more than 18" from the battery terminal. An 8 AWG ground wire (minimum) is also recommended, and attached to a metal area close to the amplifier.

Fuses: The REF-704a has two 30A ATO (blade-type) fuses installed in the amplifier behind a removable panel. A small Phillips-head screwdriver (not included) is required to remove the panel. Two spare 30A ATO fuses are also included with the amp.

Remote Turn-On: The Remote screw terminal will accept up to 10 AWG wire. Typically, an 18 AWG wire is sufficient for the turn-on lead.

Speaker-Level Input: The amp includes four bare wire-to-RCA adapters for connecting the amp to a factory radio or aftermarket head unit without preamp outputs. You should attach each speaker wire from the head unit to each adapter and plug the adapter's RCA plug 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.

Pre-Out: A third pair of RCA jacks is provided to output the audio signal to a second amplifier, if desired.

Speaker Outputs: The amp features screw terminals for connecting four speakers. There are markings on the terminals for bridging the amplifier. The terminals will accept up to 10 AWG wire.

ADAS Input: The amp offers an RJ-45 port for the input from the Advanced Driver Assistance System (ADAS), if the vehicle is so equipped.

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Customer Q&A

Q
Crutchfield asked: Why did you buy this?
A
Purchased the Infinity reference 704a solely based on Trevor's recommendation (which I asked for) on alternate components from what I had originally chosen in the JL Audio line-up. By going with Trevor's recommendations as appropriate replacements for the components I had selected previously I saved over $600!! Sure glad I made that phone call to Tech Support! [ BRADEN  Jul 21, 2018 ]
A
Value/ recommendation [ Michael  Jul 02, 2018 ]
A
To use on my infinity speakers. [ Daniel Ryan  Jun 15, 2018 ]
A
According to other opinions, this amp packs a punch, stays cool, and provides great quality sound for the price! [ Michael  May 07, 2018 ]
A
Always loved Infinity products. Bought Infinity Kappa speakers and this looks like it matches them perfectly. [ Nathan  Nov 12, 2017 ]
A
I scratched my first one, but I loved it so much I replaced it with another. [ SHAWN  Sep 22, 2017 ]
A
price and reputation [ Kirk  Apr 23, 2017 ]
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1 question already asked

Q
When setting the gains? I have all processing turned off at the head deck, when I hook up the DMM to the amplifier with the gain completely turned down and crossover set at full, a already get an amplified measurement. Is this normal or do I have a defective unit on my hands? This is the first time I encounter this when setting gains on an amp.
[ Felix  Sep 20, 2018 ]
2 answers
A
I had mine professionally installed. So I wouldn't be able to answer that
[ Samuel  Oct 02, 2018 ]
A
I believe you will always have a slight signal even with it off. Mine plays with it off too but only minimally. May be worse with yours if you have a high volt deck.Should be fine. Unless you hear noise or crackling.
[ RUSSELL  Oct 02, 2018 ]

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