Features

Overview: The Infinity Marine M4555A is a 5-channel amplifier designed to power speakers and subwoofers 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 M4555A delivers the following power output (<1% THD, 14.4 VDC):

• Full Range Channels:
  • 45 watts RMS x 4 at 4 ohms
  • 65 watts RMS x 4 at 2 ohms
  • 130 watts RMS x 2 at 4 ohms bridged
• Subwoofer Channel:
  • 320 watts RMS x 1 at 4 ohms
  • 500 watts RMS x 1 at 2 ohms

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 M4555A'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 for the front and rear channels that can be set to low pass (LPF), high pass (HPF), or Full Range. In addition, the subwoofer channel has a non-defeatable low-pass filter. You can adjust the cutoff frequency of all of the crossovers from 32Hz to 320Hz using the rotary controls.

Bass Boost: You can apply up to 9 dB of bass boost to the subwoofer channel, centered at 45 Hz, using the rotary control.

Phase: You can switch the phase of the subwoofer output from 0° to 180°.

Terminals: The Infinity M4555A 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 4 AWG power wire to the battery, with an in-line 100A fuse installed no more than 18" from the battery terminal. A 4 AWG ground wire (minimum) is also recommended, and attached to a metal area close to the amplifier.

Fuses: The M4555A has three 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. Three 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 three pairs of RCA inputs for connecting stereo RCA patch cables from the head unit to the amp.

Sub Input: There is a two-way switch to select the source of the Subwoofer Channel input. If you have a dedicated RCA subwoofer output from the head unit, you can select EXT (external) on the switch and connect the RCA cable to the amp. If you do not have a dedicated subwoofer channel signal, you can select INT (internal) on the switch, and a summed signal will be derived from the full range inputs.

Speaker Outputs: The amp features screw terminals for connecting five speakers. There are markings on the terminals for bridging the front and rear channels of the amplifier. The terminals will accept up to 10 AWG wire.