Up to 87% efficiency thanks to ADC (Advanced D-Class) 1 stable output stage ensuring high audio performance in a compact size. ^^ USS (Universal Speakers Simulators) allows SP 1.900 to work with head units featuring the speaker load detection circuit. ^^ 1000 W RMS (1) with ultra-compact size 211.6 x 130 x 49 / 8.3 x 5.1 x 1.9 (mm/inch). ^^ IP55 aluminum chassis for maximum protection against humidity and external agents. ^^ There is no cooling fan to prevent internal accumulation of dirt.