MB Quart NA2-500.5 Five-Channel Powersports Amplifier

The MB Quart NA2-500.5 is a compact five-channel Class D amplifier designed for marine and powersports audio systems. It combines four full-range channels with a dedicated subwoofer channel, allowing one amplifier to support speakers and bass in the same installation. Its compact format helps solve space limitations common in boats, UTVs, ATVs, and similar vehicles.

This amplifier is intended for system builders who want to power front and rear speakers while adding a subwoofer channel without installing separate amplifiers. At 4 ohms, it is rated for 4 x 40 watts plus 1 x 100 watts; at 2 ohms, published output is 4 x 80 watts plus 1 x 200 watts. The five-channel layout supports a balanced system with full-range output and dedicated low-frequency reinforcement.

The NA2-500.5 uses full-range Class D topology and a PWM MOSFET power supply to deliver power from a small aluminum heatsink chassis. Its Q-Stasis preamplifier stage is designed to reduce incoming source noise, while nickel-plated RCA inputs support corrosion-resistant signal connections. A signal-to-noise ratio greater than 90 dB and a 20 Hz to 20 kHz frequency response support clear system playback.

Built-in signal controls make it practical for mixed speaker-and-subwoofer systems. Front and rear channels use switched full-range or high-pass operation, while the subwoofer channel uses a variable low-pass filter from 50 Hz to 150 Hz. The amplifier also provides bass boost adjustment at 45 Hz and includes a wired bass remote for convenient level adjustment.

For marine and powersports installations, the NA2-500.5 uses conformal-coated circuit boards and marine-grade protection intended to resist moisture and salt-spray exposure. Quick-disconnect wiring connections can simplify seasonal removal or service access. It is a suitable upgrade path for a compact multi-speaker system that also needs a dedicated subwoofer channel.

Key Features

• Five-Channel Layout: Powers four full-range channels plus one dedicated subwoofer channel.
• Class D Amplification: Delivers efficient output from a compact amplifier chassis.
• 2-Ohm Capability: Published ratings support 2-ohm speaker and subwoofer loads.
• Variable Subwoofer LPF: Adjusts low-pass crossover frequency from 50 Hz to 150 Hz.
• Marine-Grade Protection: Conformal-coated boards help resist moisture and salt-spray exposure.
• Wired Bass Remote: Allows convenient adjustment of bass level from the vehicle.

Design & Installation

The NA2-500.5 has a black compact chassis with an aluminum heatsink, nickel-plated connections, and quick-disconnect wiring provisions. Its full-range Class D architecture, PWM MOSFET power supply, and Simpatico Coil Design are engineered for efficient operation in a small footprint. Three-stage LED protection diagnostics monitor thermal, overload, DC, and speaker-short conditions.

Install the amplifier in a secure, ventilated location away from direct water exposure, using appropriate power, ground, speaker, and RCA wiring. The installation guide identifies a 40-amp fuse and 8-gauge power cable for this model. Configure the front and rear channels for full-range or high-pass use, then use the dedicated low-pass-filtered fifth channel for a compatible subwoofer.