Those magical days when the HVAC is off

@carlsbad2 correct. Just turning off AC, what about all the other contaminating electrical devices still running in your home, all of it continuing to contaminate AC. And then think about the entire AC grid, we increasingly live in a 24 hour world, I suspect for vast majority of us, grid contamination pretty much same day or night.

The biggest variable day to night is both home generated and externally generated background noise. Also, I can understand why some dismiss this as cause so easily, many live 24/7 in  high ambient noise level environments, we subconsciously block much of it out. And think about epidemic levels of hearing loss today, likely many of us suffer from it and don't even know it. Not only certain frequencies can suffer, but low level info and micro dynamics simply unheard. Think about how many of us not really hearing full potential of our systems, between ambient noise and hearing loss, could be a lot!. people simply don't know what silence sounds like anymore. Go to an anechoic sound chamber, you'll be freaked how loud just your breathing is.

@sns 100% agree that I think the big difference is background noise, both inside and outside the home.  For a second I thought I was accidentally reading my own post.

Late night is great 'round here. '20's background until MOMA flies over...but somebody's getting saved potentially....  my ambient is low otherwise..

Night temps are drifting down into the '60's. so the AC can get shut down...

I’m not sure if this has been mentioned already, but I’ve had this exact experience and my sister pretty much always sounded better after 8 o’clock at night.

I do use conditioner and that helps some.  Pretty good success with running my stereo off a large battery.  It’s worth experimenting with both of these Options.

I would say the most dramatic results that I’ve heard are with a DC blocker.  DC current alter the sound by adding noise and distortion typically caused by HVAC solar panels and so on and I think it’s going to continue to be a bigger problem with being noisy and dirty and electronic devices as those devices proliferate throughout our homes and neighborhoods.

but not all DC blockers are created equal.  There’s a synchro Uni that I’ve settled on for a price that I can live with and it works wonders.  There are also cheap blockers which claim to do the same thing, but do not.

As always trust your ears.

I may Ido a YouTube video on this. It’s a good topic. It’s worth it.

 - American audiophile 

A couple months ago,,,,,plugged vacuum into kitchen wall outlet.  Dead outlet with no warning.  2 plugs on that wall both show dead.  Original 30 year old contractor grade,, so I replace with commercial grade.  Still dead.  One plug is end of circuit and the other feeds that one, and is fed (shows hot), and a second line out that goes ?   Isolating with breakers shows those plugs are part of adjoining bedroom circuit which tests out fine.  From the basement view it appeared kitchen fed bedroom.  After a week of mulling this over, I called a commercial electrician friend to look at it.  Didn’t make sense to him either.  He looked at the breaker box which looked superficially looked fine.  While gently probing neutral bar with a wooden dowel we saw very fine arcing around connections.  He recommended residential electrician…soon.   Hang in there, this story goes somewhere.   All bedroom plugs tested fine, but gotta start somewhere.  I removed the cover off of plug that appeared to be connected to kitchen.  Ok ,, bedroom feeds kitchen.  Neutral wire from kitchen still attached, but scorched, insulation gone, with the metal on the plug scorched.  That plug still functioning and tested good.  Replace that plug and incoming neutral wire.  That was that.  But,, that arcing neutral bar in breaker box.  Yup, very fine static like arcing still there.  I threw the main breaker and began to retighten all the screws on the neutral bar.  Many needed 1/4 to 1/2 turn to snug down.  No more arcing.  Nice.   So finally here’s the payoff.  The next day I resume my daily music ritual.  The improvement in audio was amazing.  Bigger cleaner wider, and especially airy.  Like upgraded equipment.  Weeks later, it’s still there. The wiring is the only thing in the house that changed.