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

You can simply improve power. Direct lines, made of audiophile wire, you can go further on that… I think it was Stereophile last month about complete home power equipment replacement. On the digital end there is an Ethernet regenerated… and / or audiophile router. But like all things you have to balance cost with benefit and where else you could have spent the money.

After I reach a new level with my equipment… I occasionally do a small upgrade to see it’s effect… until there isn’t much (really never happened). I added a second direct line for my amp recently… it made a significant improvement. 

I totally agree with this.  I liken listening at night versus during the day as listening with a good power conditioner versus plugged into the wall.  It’s like our whole “perceived” noise floor of the world declines significantly at night.  I can’t measure it and can’t come close to explaining it, but if I really wanna explore the differences between gear I do it at night and not during the day.  That’s the best I can describe it.  Just my $0.02 FWIW. 

Let’s not ignore another more humanistic factor that may come into play here, in that one may feel more relaxed and receptive in ones self at such a time of day, for my part I find a nice glass of 20 yr old single malt contributes enormously .

Agree with tsushima1 ... I have found that my music sounds better when I'm relaxed and have got nothing else on my mind. This is true regardless of the time of the day.

No question, there is a humanistic factor. But the fact that the analog sound doesn't change very much throughout the day indicates that there is something else going on.