Help with buzz / hum that's making me insane r

I've recently realized that there's a very very subtle buzz or hum coming from the dome tweeters of BOTH of my Dali's that's audible if my ears are right next to them. Now before everyone says the tweeters are blown, let me take you through what I've done to analyze the situation (it could also be that I'm crazy):

Hooked up Dali's to a different amp using same front end, still hum
Hooked up different speakers to amp/front end, still hum
Swapped around ICs (I'm running balanced on DAC and Phono), still hum
Rewired system making sure PCs and ICs aren't touching, still hum
Hum is present with both vinyl and digital

The sound is still very, very good, but I can't help feel like on higher register vocals I can hear just a touch of distortion that I wasn't hearing before. Again, this is on both channels, and the sound is great, but vocals and highs have a small touch of rasp. I can't tell if this is me being crazy, because I can hear the hum from the dome tweeters when my ear is right next to them. Any ideas of ways to play around to see what the problem is.

I'm using shunyata PCs for the most part (one cardas) and a Hydra 6 into a Shunyata outlet. Help is greatly appreciated, as this is driving me nuts