A DACs analog output interconnect cable is a galvanic conduit for RF noise from downstream entering the DAC to affect the transparency of the D/A conversion. So, simultaneous with a DACs audio signal going out to the amplifier (or preamp), RF noise also comes back in. This noise is generated from AC connected components or magnetically induced through cables acting as antenna.
RF•STOP™ EXTREME Signal Filter uses skin effect filtering technology for bi-directional low pass filtering. It allows full bandwidth audio to pass while blocking higher frequencies. As per the attached diagram, install RF•STOP using ultra short interconnects where possible.