Soundstream REF2.640 2 x 190 2-Channel Amplifier (Midnight Blue) Sequenced Delays Eliminate Residual Power-Up/Power-Down Pops  Differential RCA Inputs Isolate 12V/Audio to Ground Eliminating Ground Loops and Noise  Full Signal Path Low Noise/Distortion Circuitry Topology Triple Darlington Audio Output Stages  Differential Drives Divide Pre-Amp & Power-Amp Stages Eliminating Ground Looping  Full Differential Feedback Surrounding Power-Amp Stages directly from Speaker Terminals Output Stage Bias Individually Sequenced Optimizing Sound Quality  Stout 2 Oz. Copper Traces Effortlessly Transfer High Volume Internal Current  Close Tolerance Signal Path Components - 1% Resistors & 5% Capacitors Hawkins Boost Control - Proprietary Bass Equalization Continuously Variable Crossovers  Tri-Mode Capable