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Infinity M704A

4-channel marine amplifier — 70 watts RMS x 4

Item # 108M704A

Do you want to bring the party on board? Infinity's handsome M704A marine amplifier will add a lot of happy to...

Do you want to bring the party on board? Infinity's handsome M704A marine amplifier will add a lot of happy to...

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Item # 108M704A

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$349.99

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About the Infinity M704A

Power delivered in style

Do you want to bring the party on board? Infinity's handsome M704A marine amplifier will add a lot of happy to your music, sending 70 watts RMS to each of four speakers. The amp could also power two speakers and a sub, in 3-channel mode. For even louder fun, you could bridge the amp to 2-channel mode and power a couple high-performance speakers with 200 watts RMS each. The amp features a coated circuit board and stainless-steel connectors that will stand up to the sun, salt, and spray.

Power delivered in style

Do you want to bring the party on board? Infinity's handsome M704A marine amplifier will add a lot of happy to your music, sending 70 watts RMS to each of four speakers. The amp could also power two speakers and a sub, in 3-channel mode. For even louder fun, you could bridge the amp to 2-channel mode and power a couple high-performance speakers with 200 watts RMS each. The amp features a coated circuit board and stainless-steel connectors that will stand up to the sun, salt, and spray.

Works with almost any system

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

Infinity M704A

M704A power and speaker connections

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Product highlights:

  • 4-channel marine 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
  • conformal-coated circuit board and stainless steel connections resist salt water corrosion
  • preamp and speaker-level inputs
    • high-level input adapter included
  • preamp outputs
  • fuse rating: 30A x 2
  • wiring and hardware not included with amplifier
    • 8-gauge power and ground leads recommended
  • dimensions: 14-1/8"W x 2-3/16"H x 7-3/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee
  • MFR # M704A

What's in the box:

  • 4-Channel Marine amplifier with two 30A ATO fuses installed
  • 2 Spare 30A ATO fuses
  • 4 Speaker wire-to-RCA adapters
  • 4 Self-tapping screws (length 2")
  • Quick Connect Guide
  • 2 Infinity decals

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Great Marine Amp.

Alvin from Florence, SC on 7/30/2018

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installed connected to Infinity PRV-250 receiver in my 19ft center console SeaHunt Triton 188 along four infinity 652 6.5 inch speakers sounds great much better than receiver without amp. Great Amplifier for the money.

Pros: Compact design

Cons: none

Crutchfield response on

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Product Research

Features

Overview: The Infinity Marine M704A is a 4-channel amplifier designed to power speakers aboard a boat or in an environment where moisture or water spray may be present. Infinity Marine amplifiers are engineered with conformal-coated circuit boards and other protections to withstand harsh marine conditions. In addition, the amp includes stainless steel mounting hardware that is resistant to corrosion.

Power Output: The M704A 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.

Gain: The M704A'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.

Terminals: The Infinity M704A 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). The tops of the terminals are covered by a rubber plug to prevent water from entering the amplifier.

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 M704A 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.

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Customer Q&A

Q
Crutchfield asked: Why did you buy this?
A
Was torn between this amp and the 40w rms high power Sony marine head unit. Decided to go with this and the lower powered (but cheaper) Kenwood head unit, so I'm not kicking myself later for not giving my speakers the power they're rated for. [ Dustin  Jun 05, 2019 ]
A
Infinity quality at a good price. Plus it comes with speaker level inputs. [ Denver  Nov 28, 2018 ]

1 question already asked

Q
Can I bridge this amp on a sub and also run stereo on the same 2 channels. At 3 or 4 ohms? Will it handle it. 8 ohm sub and 4 ohm 6 1/4" s?
[ Raydog  Jul 18, 2019 ]
1 answer
A
Yes you can run the front channels at a different impedance even if you bridge the rear. The amp is 4 ohm stable in bridged mode and puts out 200 watts RMS. If your sub is 8 ohm you would probably only get around half that power.
[ Cosmo  Aug 03, 2019 ]  Staff

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