The UD-064/UD-064D is a high efficient switching power amplifier with a concise and intuitive digital control interface. The amplifier is designed to achieve its maximum output by paralleling speakers on its outputs. Every output of the amplifier can deliver 600W of power on 4Ω load of parallelized speakers and over a kilowatt of power on 2Ω load. The outputs also support bridging which can drastically extend output capability up to 2 kilowatts on each bridged pair. It comes with an unprecedented eXtraTone™ mechanism to compensate speaker for loss below its bass cutoff. Besides boosting the bass audio on cutoff frequency of the speakers, eXtraTone™ mirrors the audio below the cutoff frequency in a way of harmonic audio over a range of frequency above the cutoff frequency.