Streaming music sounds better late at night. Is this just me?

kijanski,

I don't know much about the ionosphere, but are you saying that the SQ improves at night because of the radical shifts in the ionospheric layers rather than the reduced stress on the power grid?

@chungjh   Reducing transmitting power reduces pollution from electromagnetic waves as well as pollution of the grid by radio stations.  

My system tends to sound best late at night ~11PM and the very best on Sunday night. I have noticed this for forty years with different systems, in Arizona and Washington. 

OK, is there anything we can do about this? I already have a very good power isolator Torus RM20.

We had few discussions on this subject and so far nobody has been able to pinpoint the reason for improved sound at night.  I suspect that all factors play small role, including electrical grid pollution, reduced AM waves, reduced cellphone traffic etc.  
There will be some noise injected from the Ethernet.  Ethernet has inherent isolation, but nothing is perfect (there are always few pF across).  Perhaps some ethernet filtering might help, but I don't know much about it.  Other than that, usual precautions, like running signal and speaker cables away from (or perpendicular to) power cables, proper grounding and shielding etc.