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.
jwminf9e7
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Definitely, power -- may I be so definite? The local electrician was absolutely definite on this point (no joke). He mentioned the TV, too.
I live in the old continent; my 230V equipment refuses to reproduce clear bass under 220V. I claim to "hear" the difference when the neighbours' stove & heater switches off--through my speakers. Easy to do when you live, as I, in a flat...
But then, how often can we stay up to 3am to enjoy music?
A very good thread indeed! All above posts bring out the real experiences and make sense from engineering principles. I too found various successes in using some of the methods mentioned. However, i have a little reservation on Oatalay's method of cutting the pc into shorter lengths. Best to check with Powersnakes what's the MINIMUM length which will do the job. In eng'g sense, the conductor size, dielectric material, geometry(twist & formation), grounding and length all account to the effective "filtration" the pc designer is aiming to achieve.
I use Chang CLS6400 ISO, NBS Dragonfly II & AudioPower 313(obsolete?) pc's. They are not top of the line but they do a fine job on my tubed system which has a low current demand. I changed the Chang's feeder to a Belden foil shielded 3X14 Awg powersupply cable; connecting the drainwire to Chang's metal chassis, thus voiding my warranty right. I did this because my 20A powersocket is wired through metal conduits. The foil & drainwire serve as an extension of the conduit system. Please do not attempt this unless you are a qualified electrician. Regards.