The dissipation system is optimized with the heat being transferred to the heat sink and then dissipated through the sides of the amplifier. Compact Design Built from Extruded Aluminum Heatsink with the Top Side E.Hertz Compact Power HCP-4D D-Class 4 Channel Amplifier 145 WRMS x 4 at 2-Ohm. Compact Design Built from Extruded Aluminum Heatsink with the Top Side Ensuring Effective Transfer of Heat. Special Balanced High-Noise Rejection Input Circuitry on the Pre-In or Speaker-In Inputs. Speaker-In (For OEM Head Units) and RCA-In (For Aftermarket Head Units) Inputs.