System sounds better at night?

I have noticed that my system sounds MUCH better at night, after about 10pm than at any other time of day. It is clearer, more open and transparent, with a blacker background. Another audiophile told me that this is not real, it's just that there is less noise in the household at night. I disagree in that what I hear (or don't hear) is not simply due to less ambient noise but rather cleaner sound. Will power line conditioners simulate these effects during the day? Has anyone else noticed this and what is the most effective way to get better sound during the daytime? Serious responses only, please.
Tell your buddy that someone is "smokin' somethin'" but it's not you. This is a common occurance and you are not alone in your findings. My systems typically sounds noticeably better after about 1 or 2 in the morning. Soundstage becomes far more vivid and detailed, there is a "haze" or "grunge" that is removed, everything becomes more lucid, etc.... While i wish that i could achieve these results all the time, it is probably not achievable unless one has their own generator system to plug into or the capability of being able to run everything off batteries. Sean
check out steve deckert's musings on his site great stuff, some speculative, about late night listening.
it has to do with fewer draws on the power grid from the general public at night; more relaxed state of mind at night?; less ambient light means more concentration on sounds instead of sights; different electrical characteristics while insulated from the sun...all these things add up!
My system goes into this super quiet hyper-drive mode about 11 PM every night-- it's a well known phenomenon among audiophiles as Sean notes above.

As to achieving this quality during the day; putting in a dedicated AC system, ground system, high quality power cords, and getting rid of my power conditioner helped a lot. But even then, the 11 PM effect became even more pronounced. Cheers. Craig.
I tell the truth. I now have most of the atributes from this condition with my preamp and CD player pluged into a PS audio Power Plant 300, and Sonic Horizons Skyline A/C power cords, and dedicated lines. This is not an ad. I paid for it all. But I live in power ravaged Southern Calif. with all kinds of industrial pollution. I still get a more refined musical experiance at night. But I also get a very much improved sound all day. Maybe it is just that I am less than 5 miles from Disneyland and all that happiness makes the the Power Plant sound better.
This might help?
If the humidity where you live is 70% or above, your sound
system will sound dead & lifeless.the highs will bounce off
the airborne microscopic water particles & render the sound lifeless.this is one of the main reasons people love & hate their audio gear.Adding a dehumidifier in your audio room will make your system sound system sounds best in the evenings when the humidity is usually lesson in audio technology!
Not only do AC lines have lower demands placed upon them, much of what is heard in sonic improvements at night is due to reduced activity from traffic, construction, etc.The low frequency waves generated are extremely powerful and disruptive and can travel dozens of miles without dissipating.

MP your idea about humidity goes against the jist of the other postings. Humidity goes up at night as the temperature falls closer to the dew point. Everyone is saying there systems improve (at night with higher relative humidities) so a dehumidifier would go the other way. If anything you need to add a humidifier. Don't think so....
This was interesting to read as I noticed this in years past and just chalked it up to less distractions. My brother told me he noticed this also not long ago. Now I read there may be some truth to it!!!
My system alway's sound's better to me at 3:00 or 4:00am, too think I thought it was the case of beer I drank and all the women that were coming over from the bar! Well that still might be some of it!
Mine also sounds better at night. At night people are in bed sleeping so you have fewer electricity poluting things on line. I found that as I go around turning things off for the night my system gets quieter.

Your neighbors polute your electricity. Things like fluorescent lights, TVs, dimmer swithches. These things and many more put garbage in the electrical system which shows up in the background of your system.
late at night when all the irritations have ebbed, one is relaxed, frostie or warm red, the ambience plays a big roll as one usually listens at a lower volume with a touch more system sounds incredible when i am the only one up.Mains power is always spot on where i live,another point is all the electrical things like fl globes are off...its not in the mind..its real.Music soothes the soul.

It could also be the giant EMI emitter is on the other side of the world  ;) 
No solar flare or sunspot activity at night, much reduced seismic vibration due to automobiles, buses, subways, less cell phone activity.
Interesting to see my OP from 2001 and I still feel the same way about day vs nighttime listening.  While I have not found a line conditioner I like, judicious placement of an isolation transformer has helped.
OP: per your search for a power conditioner, check my posts about Inakustik AC-3500P on the following thread:
@celander  Did you purchase in US and if so from whom?  I'm guessing this is $$$.
A lot of RF is airborne, that why cell phones work indoors, and generated by microprocessors in electronics so power conditions isn’t going to help that. Just saying. 
Daytime enjoyment of one’s audio system is hampered by so many things. Solar radiation, demand on the power grid of local utilities, consumer products being used in home, increased airborne particulates, etc.
For those who use the Inakustik AC-3500P, are you plugging your power amp into this conditioner?  What about your digital gear?
For my system, a pair of ATC SCM20-2 active monitors (built-in amps and x-overs), Jay’s Audio CDT2 MK2 CD Transport, Theta Digital DSPro Basic IIIa DAC and Oppo SE83 blu-ray player are plugged into the unit. My preamp, Teo Audio’s The Liquid Pre, is a passive unit that does not require power.
Since each outlet of the Inakustik AC-3500P is configured in parallel to the other outlets, all outlets have as much power line feed as the others. This is not the case with certain other conditioners (or so-called power distribution centers) in which the outlets are linked together in series (aka daisy-chained). In those cases, the first outlet served from the wall or internal circuit gets the feast of all available power while the last outlet in the chain gets the famine.