Well, some reviews claim "The Innuos PhoenixNET will also improve your music playback from the files on the music server itself. Even though that music isn’t being streamed through the PhoenixNET. You heard that right."
Well.... something not even connected somehow improves the sound. OK.
Some digging around revealed that, for example, Ethernet does not do error correction. it does discard corrupt frames though. and TCP will retransmit lost packets. So the switch may be simply buffering frames and then transmitting in sequence on cable with fewer dropped packets. How does it affect the sound? Depends on quality of the streamer.
@nigeltheflash - Do you mean RFI on the twisted pair or in the space around the unit? Simple shielding or or galvanic isolation would drastically reduce RFI. Not sure about necessity of switch for that purpose since it runs its own CPU and hence makes its own RFI.