2-channel Inline Common-mode Speaker Line Filter with 2 Neutrik SpeakONs The Common Mode Speaker Line Filter (JPB-2016) is used to eliminate undesirable heterodyne tones caused by capacitive coupling of multiple Class D power amplifier outputs. Heterodyning is the combination of two or more frequencies to create sum and difference tones, in this case within the audible range. Heterodyne tones can occur when output cables from more than one Class D amplifier are run close together over a long distance, even with no audio signal present. Ashly Class-D amplifiers currently include all nX, NE two-channel, NE multi-channel, Pema, SRA, and TRA models. The JPB-2016 is wired using Neutrik? speak-ON NL-2 or NL-4 type connectors.