Dedicated 20 amp lines/should i use a sub panel

If the cap have to be in use to reduce noise, I think it is worth to confirm that if the C13 ( .03 600V ) been modified and connected across the Hot and Neutral, the cap should be a class X cap, and if the cap is connected from Neutral to chassis then a class Y cap must be used.
https://www.allaboutcircuits.com/uploads/articles/ND_x-class_y-class_safety_figure2.jpg

https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/

Hello,
I have a question for this group regarding an issue likely related to power that I face time to time in my music room. It seems that audio/video quality fluctuates during the day/evening and I get the best quality (audio/video) only after midnight. I have two dedicated 20 Amp circuits (10 gauge wire) with a pair of Furutech receptacles which feed all of my AV components. I don't have any power conditioner but use a Nordost power distribution unit. My system is relatively quiet with no 60 hz hum. However there a slight hiss that comes out of my Aerial Model 7T speakers when everything is powered on but it is only audible if you take your ears very close to the tweeter.
Could anybody comment on the possible root cause behind the inconsistent audio quality throughout the day?
I am thinking of installing a balanced power transformer but not sure if that (isolation) would address the inconsistency issue. I would love to hear your opinion on this as well.
Thanks.

Welcome to the perennial problem of dirty power. Turn off all dimmers and use only incandescent bulbs. Heating boilers, appliance motors, phone charging adapters etc all add noise. Note that your hearing is more sensitive late at night so music sounds better then.

@indranilsen, AC power coming into our homes is always in a state of change. Fewer people up after midnight using power so the incoming AC could be less polluted as noromance stated.

A balanced power transformer could possibly allow you to hear more details in the music and maybe even a better soundstage however it might not necessarily get rid of the slight hiss you hear from your tweeter.
Personally, I wouldn't be concerned of the hiss.