HB 48 II 4A

The Zapco HB 48 II 4A is an eight-channel digital signal processor with a four-channel Class AB amplifier built in. The amplifier section powers a front and rear speaker set at 23W RMS per channel at 4 ohms, 35W RMS at 2 ohms, and up to 70W peak, while the processor keeps eight channels of tuning available for the rest of the system.

That split is the point: four channels of onboard power for the speakers you have now, plus eight RCA outputs for external amplifiers as you add a subwoofer, a center channel or a three-way front stage. Four high-level inputs pull signal from a factory radio, and two RCA inputs cover an aftermarket source.

Tuning tools include 31-band equalization, an I/O mixing matrix, Butterworth, Bessel and Linkwitz-Riley crossovers with slopes from 6 to 48 dB/oct, speaker assignment, time delay, level and polarity. Work from PC software for a full tuning session, or from the Zapco app when you want to adjust presets in the car. Bluetooth streaming and the USB Music Player function add sources without changing the head unit, and the optional remote brings volume, subwoofer level, presets, source and track control to the dash.

The 160 x 126 x 45.5 mm chassis installs under a seat, behind a glovebox or in a marine console, so a staged build can start with the factory radio and grow one amplifier at a time.