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
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
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
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.