MB Quart NA3-560.4 4-Channel Marine Amplifier

The MB Quart NA3-560.4 is a four-channel marine amplifier designed to add clean, configurable power to boat, powersports, and weather-exposed audio systems. It delivers up to 70 watts RMS per channel at 4 ohms or 140 watts RMS per channel at 2 ohms. This makes it suitable for powering four full-range marine speakers from a compatible source unit.

Its four-channel layout gives installers flexibility for balanced multi-speaker systems, including front-and-rear zone arrangements. Each channel pair can also be bridged, allowing the amplifier to provide up to 280 watts RMS per bridged pair at 4 ohms. The result is a practical option for systems that may evolve from four speakers to a mixed speaker-and-subwoofer configuration.

The NA3-560.4 uses MB Quart's Class SQ Class A/B topology, Q-Stasis preamplifier section, and FLUID-FET output devices. Its published frequency response extends from 10 Hz to 45 kHz, with a signal-to-noise ratio above 90 dB and total harmonic distortion below 0.2%. Adjustable gain, crossover, and bass-boost controls allow the amplifier to be matched to the speakers and source unit in the system.

For marine-duty use, the amplifier is IPX67 rated and uses a conformal-coated circuit board, sealed connections, and corrosion-resistant stainless-steel hardware. A gloss-white epoxy finish and heavy-duty heat sink help transfer heat away from the amplifier's output stage. The top-mounted controls are protected by a removable sealed cover.

RCA inputs support conventional preamp-level source connections, while speaker-level input capability and DC signal sensing support installations using source units without RCA outputs. The amplifier can be switched between remote turn-on and DC-sense activation modes. It is a focused power-amplifier upgrade, so a compatible source unit, speakers, power wiring, ground connection, and correctly sized fuse are still required.

Key Features

• Four-Channel Output: Powers up to four speakers from one compact amplifier.
• 2-Ohm Power: Delivers 140 watts RMS per channel at 2 ohms.
• Bridgeable Channel Pairs: Supports two 280-watt RMS bridged channels at 4 ohms.
• IPX67 Marine Protection: Built for water- and dust-resistant marine installations.
• Variable Crossovers: Helps route appropriate frequencies to speakers or subwoofers.
• DC Signal Sensing: Supports turn-on with compatible speaker-level source signals.

Design & Installation

The NA3-560.4 combines a gloss-white epoxy exterior, heavy-duty heat sink, conformal-coated circuit board, sealed connection points, and stainless-steel hardware for marine-oriented durability. Its top-mounted tuning controls sit beneath a removable cover that should be reinstalled after adjustment. The amplifier also includes illuminated status indicators for overload and speaker-short protection monitoring.

Mount the amplifier securely in a location with adequate ventilation and do not mount it upside down. Use high-quality 10 AWG copper power and ground cable, install a 35-amp fuse within 18 inches of the battery connection, and use the included harnesses for power and speaker connections. Set gain as a signal-matching control rather than as a volume control, then select full-range, high-pass, or low-pass crossover operation for the connected speakers.