I experience the same thing. Lots of microwave energy where I live (near Cape Canaveral, KSC) also there is more active radio interference during the day than late in the evening or early morning. Without some type of filtering there isn't much you can do. Sounds like you might want to check out one of those PS Audio P300 power generators, would certainly help you with clean power and filtering out the nasties that is affecting enjoyment of the system. I bought a pair of Enacoms passive RFI filters, that helped. Audio Prism also has a product called quiet lines that plug into the wall outlet I have heard that the work well. Both of the above are inexpensive and are probably a good place to start.
Different & inconsistent sound quality
I am noticing different sound quality from my audio system, depending on when I listen to them. My system consists of Krell integrated amp, B&W CDM 1SE, and Sony DVP-7700. They are connected with Transparent ML Super interconnect and MIT T2 Biwire speaker cable. For example, in the moring and very late night, piano recordings sound very clean, detailed, and transparent, however, in late afternoon or evening, it seems that some of piano notes from the same CD sound very dull and veiled. The phenomenon is true of other recordings of cello, violin, and etc. I suspect that AC noise has to do with the problem, so as a first step, I consider upgrading stock power cord for my integrated amp to a better one such as Transparent PowerLink Super or others. Could anyone help me with any possible solutions to the problem I'm experiencing? Any suggestions or comments would be greatly appreciated.