What's Going On?? Sound changes every night


O.K., this is what I'm experiencing: Some nights my system is superb and I just get sucked in and have to force myself to stop. This will be for 2-3 night and then all of a sudden, the next night or three, the music looses life and I can't get involved. The sound looses high end sparkle and extension. Things sound closed in a bit and percussions instruments that the night before were right in front of me are now fake with a closed in and shelved down presentation. Cymbals no longer sound like wood sticks on bronze but as if someone threw a blanket btw me and them.

Is this a power conditioning problem? I use a hospital grade outlet but not a dedicated circuit and no power conditioners. Or could it be my DAC which is a Perp Tech w/ Level 2 WrightMods and cryo treament. When the system works right I couldn't be happier but it seems something weird is going on every few days or so. Could it possibly be coming from the local power company and I need some sort of powerful line conditioner?

System:

Merlin TSM-MX speakers
REL Strata III subwoofer
Air Tight ATM300 stereo amp
Joule-Electra LA150 pre-amp
WrightModded Perp Tech DAC
CEC transport or Marantz SE 5 disc changer as transport
Cardas Golden Reference interconnects
TG Audio speaker cables
tomryan
Stehno makes a key point in that dedicated lines will not clean up the AC from outside your home, and unless you have a dedicated ground on that dedicated circuit you will still get feedback from other appliances in the house. I have 3 dedicated lines (10 guage, 20 amp, power ports) but grounding those on existing ground did nothing to alleviate EMI from other appliances. Some use a seperate (dedicated) ground for their dedicated lines but I've heard this can be potentially hazardous because of potential between the 2 grounds.
Even after the dedicated lines I heard variable quality from system so I went to power condtioning as well. Originally PS300 on sources only, now I have BPT 3.5 Sig. on everything. No variability anymore, noise floor has dropped considerably, stable image, etc. If you have dirty AC this is the way to go.
I have noticed this also. I believe a large contributor is background noise. Later in the evening less traffic, clearer sound. Wind and humidity also bring traffic "closer" to your house. Days when your furnace or AC are running frequently or the wind is strong also muddy the sound.