Lanzar Parametric Equalizer with Subwoofer Gain Control 9-Volt RMS Pre-Amp
You may use the RCA output to connect a power amplifier, then connect the passive speakers and the RCA inputs for MP3, DVD, or Phone. It also has a bass equalizer, mid-bass equalizer, mid equalizer 1 KHz-2 KHZ high equalizer and each frequency adjustable has a -12dB to +12dB.