I'm currently listening to a Synergistic Research demo switch. Although this one is thoroughly broken in, it took two days to open up. Previously, I thought the Synergistic stuff was fairly far on the voodoo side of the continuum. But, if I use an active switch, I prefer a compact, one-piece unit that is complete as is. As I said to a friend who is an audiophile: My mind is skeptical but my ears remain open.
For this experiment, the switch sits close to the router, which resides in a different room from hifi. Therefore, the patch cable from the switch feeds the in-wall ethernet, which eventually feeds a passive filter and the MU2 streamer/DAC (this is the only wired connection to the router). I know that most manufacturers suggest getting the switch as close to the streamer as possible, but this setup is easy to implement and get a feel for the gear.
After two days, the main effect was an increased sense of depth. The sound does not move closer to the listener, an effect I do not prefer, instead one hears more of the size of venue, as if the soundstage extends further to the rear of the speakers. Better yet, it seems airier (but not lacking in impact in any way). Similar to using a diffuser but perhaps 10x that effect. The overall effortless flow of the music also increases. I believe both of these are not sound effects, but result from a lower noise floor that allows the true qualities of the MU2 to be heard.
Next, I inserted the small UEF ethernet filter into an unused RJ45 port of the switch. Very disappointing. Suddenly, the switch's beneficial qualities were diminished. After an hour, I almost removed the filter at that point. Give me back the good stuff! But, assuming that the designer had his reasons for this option, I just let the music play in the background for a few more hours.
After a few hours, I wanted to listen to one song from Pat Metheny's MoonDial, but before I had realized it I had listened to the whole album. The timbre of his specially designed baritone guitar with its highly specialized nylon strings was effortlessly revealed. As was his intricate playing. What came to mind was not "this sounds real" but "this is so beautiful."
In short, so far, so good. Will keep listening. Down the road I will substitute the SR-included power cord with a Kubala-Sosna PC since I have one available.