what could have happened?

Two suggestions

First, unplug all cables and clean and re-attach. Sometimes it is suprising what it can do.
Second, check you speakers. Would be worried about a tweeter issue. If you have a left right "selector" on your amp, try to compare them and see if they sound different..

You may want to check all other outlets in house (including garage).

I use two different Powervars, the ABC 1200 for HT and the ABC 600 for analog. They seem to work fine and were considerably less than many name brands. I also have Audio Prism "Quiet lines" on each circuit. There are a number of quality conditioners around (if I had the money, I'd opt for Blue Circle).

I've had good results with the PS Audio UPC-200. If you can find one used it might be worth a try.

Good luck and let us know how it works out for you.

thanks guys. i was looking at ps-audio upc-200 or the powervar abc or the blue circle hum buster(though i don't think that would condition the line)coupled with dakiom stabilizers. any comments?

there was no change in component or connectors, the sound just seemed to "change" a bit. the equipment is @ 2 months old, could it be in the terrible portion of break-in?

Plato's suggestion is a good one. If this just came about all of a sudden and haven't changed any components recently, this is a sign of AC related problems. It is possible that there was an increase in noise / interference / RFI on the line. In my experience, this type of situation manifests itself in just the way that you've described i.e. a reduction in warmth and liquidity with a more harsh, brittle sound. A lack of air, separation and black background are also further evidence of this. Either way, if can diagnose and correct this problem, please post your findings and what you did to fix it. I'm sure that others may be curious and you may help them to recognize a problem that their system is also suffering from. Sean
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If it was good sounding previously, what was the last item that you changed or added?

Backtrack your configuration to the one that sounded good and go from there...