Earthquake Sound's MiNi D amplifiers deliver unbelievable power in a compact size and stand as the most efficient Class "D" amplifiers. The MiNi D3000.4 puts a peak power output of 3000 watts and includes a subsonic filter, variable x-over, and auto signal sensing. All MiNi D Stereo Amps feature a x-over switch and frequency adjust controls, used to adjust the boosted center frequency. Bass Boost (available on the D1000.4) adds 0-12dB to the chosen center frequency. Subsonic Filter (available on the D1500.2 and D3000.4) protects your speakers from harmful low frequencies and DC voltage. And with Auto Signal Sensing, by simply connecting the RCA or speaker level inputs to the amplifier, it will turn on automatically when it senses an audio signal. Each amplifier has bridgeable IN/OUT that allows you to link two amplifiers together.