CT Sounds AT-900.1 Class D Monoblock Car Amplifier AT-900.1D Monoblock Amplifier Power Ratings- 1 ohm at 12.8v, 900W (rms), 1800W (max) 2 ohm at 12.8v, 450W (rms), 900W (max) 4 ohm at 12.8v, 225W (rms), 450W (max) Class D Amplifier Technology