M704A

The Infinity M704A is a four-channel Class D marine amplifier built to power a full boat audio system from a chassis small enough to tuck behind a helm panel or under a seat. It puts out 100W RMS per channel at 2 ohms and 70W RMS per channel at 4 ohms, with 1000W peak output on tap for dynamic passages.

Bridging changes the layout: two channels at 200W RMS each into 4 ohms, which frees you to run a pair of tower speakers hard or feed a subwoofer while the remaining channels handle cockpit speakers. Signal-to-noise ratio is rated above 85 dB, so quiet passages stay quiet at anchor.

Onboard 12 dB electronic crossovers switch between full-range, high-pass, and low-pass with variable frequency adjustment, letting you set where each pair of channels starts and stops working. That matters on the water, where cockpit speakers, tower pods, and subwoofers all need different bandwidth from the same amplifier.

Inputs cover both speaker-level and low-level sources, so the amplifier connects to a factory head unit through the four included high-level adapters or to an aftermarket source unit over RCA.

The circuit board is conformal coated for marine use, protecting the electronics against humidity, spray, and the temperature swings a boat sees between a closed cabin in July and a covered slip in January. Stainless steel mounting hardware and rubber inserts come in the box for a solid, vibration-damped mount.

It pairs directly with Infinity marine speakers and subwoofers, including the Kappa Marine series, and works as the amplifier for center-console, pontoon, and runabout systems.