"PAC SNI-1/3.5 Ground Loop Isolator w/ 3.5 mm PlugEliminates ground loop noise between the audio source and radio. For use with portable device that have the 3.5mm audio plug.? Close to perfect response of +/- .03 dB from 20-20kHz.? Unlike other manufactures which use 1:1 transformers, PAC utilizes proprietary audio transformers for a 1.3 dB gain. "