The SP4-SL is the choice for a quality, low noise equalizer. In the ZAPCO tradition, the SP4-SL has built in Line Transformers - Fader, Sub and Crossover. Utilizing balanced SymbiLink technology, this EQ may be powered from a ZAPCO Competition amplifier or a PSi-SL power supply. Get the Winners solution: A ZAPCO SP4-SL!MAX OUTPUT: 16VMAX INPUT: 5VEQ BANDS: 40,125,1K,12KT.H.D. + Noise: 100dB Frequency Response: 2Hz - 150KHz Stereo Separation: >100dBDimensions: 5.25"D x 6.25"W x 0.95"H-Four, 18dB, Boost/ Cut EQ filters centered at frequencies chosen specifically for the automotive environment.-EQ Center Frequencies: 40HZ, 125 KHz; 1KHz, 12KHz-Unbalanced RCA inputs to SymbiLink balanced output-24dB Variable, low pass, subwoofer crossover, adjustable from 30Hz to 300Hz-Subwoofer amplifier gain control-Front to rear fader control-Overall system volume control-Input gain control switchable at 0, +6, or +12 dB-Front panel power and clipping indicators