BOSS Audio B25N Ground Loop Isolator Noise Filter, Reduces High Pitched Whine Alternator Noise caused by the car's electrical system, Always Use High Quality RCA Cables for your Audio System.Dimensions: 3.4 x 1.5 x 1.5, Unit Weight: .30 Lbs. Tips: Ground each amplifier independently. Same thing if you have added stiffening capacitors, go to a separate ground for the cap. Tips: Make sure that the amplifiers have a good ground first. Use at least 10 Gauge wires for the grounds (and power). If you have 2 or more amplifiers, DO NOT go from the ground terminal of one amp to the other and then from there to ground.