Earthquake Sound TNT Series T500W/2 2-Channel 800-Watt MOSFET Amplifier with Auto Sensing 800-Watt, 2-channel class A/B amplifier Equipped with massive MOSFET power supplies and high quality circuitry for more power and a cleaner sound THD: &gt;0.008%; Signal-to-noise ratio: 95dB below rated power Power 2-Ohm: 2 x 150; Power 4-Ohm: 2 x 100; Power 4-Ohm Bridged: 1 x 300 AUTO SIGNAL SENSING - will turn on automatically when it senses an audio signal