The ZAPCO ST-104D SQ III is a compact 4-channel Class D full range amplifier designed to deliver clean, powerful audio in a space-saving footprint. It provides 100 W RMS per channel at 4Ω, which can increase to 150 W RMS at 2Ω, or be configured in bridged mode to output 2 x 300 W RMS at 4Ω for those needing more punch from a subwoofer. To ensure a precise sound, the unit maintains a signal-to-noise ratio above 90dB and a frequency response from 15Hz to 30kHz. You can fine-tune the audio using the variable input gain, electronic crossover, and bass boost controls, while the flexibility of both RCA and speaker-level inputs makes it compatible with a wide range of head units. Its small chassis, measuring 124 x 50 x 213 mm, allows you to tuck it away in tight spots under a seat or in the trunk without sacrificing performance.