(...) Typically, serious audiophiles know that a dedicated mains supply, separate from the normal household supply is required to achieve anything like decent sound. Why? A typical household supply is carried through low grade, poorly insulated, poorly screened cable with multiple, very poorly executed joins and junctions and is subject to the noise generated by dozens of switch mode power supplies, fridge and freezer compressors, light dimmers, motors, and host of other household appliances, all of which inject noise back into the system. Using household or hotel mains for high-end audio is akin to drinking water from the waste water system.
For a set of audio electronics to reach high sound quality standards independent of power supply quality, its power supplies would need to emulate the qualities of both the dedicated mains supply and any further mains conditioning that’s applied. I would submit that such a pre-amplifier and amplifier would require such an over-engineered solution as to be completely unfeasible. Personally I am not aware of any hi-fi electronics that have not been improved by better mains isolation and noise reduction, which according to the logic of the above statement would mean that all the systems that have respond positively to mains improvements are flawed In some respect. (...)
Well ... Should we split audiophiles in two categories, the few serious audiophiles that have a dedicated mains supply and the many non- serious audiophiles that do not have dedicated mains?
I can't write about typical household supplies, mine does not have any of the poor characteristics you refer - it was built with decent quality electrical materials from known brands. Besides I have three dedicated separate power lines in my listening room. In my system I have found that I prefer hooking the whole system on a single dedicated line.
I can connect the whole system to the house power supply or the dedicated lines in a few seconds. Although there is a difference, it is not a night and day difference - much less than for example than just changing power cables. Surely each case is a different case!
IMHO grounding aspects are much more important than just supplying the power. And experts in the field disagree on the optimum layout of power lines for audio systems - as soon we research the subject we find contradictory views on it. Mains isolation and filtering should be avoided according to some people I respect in this hobby. Remember that some devices people call "grounding boxes" are just tuned noise injectors ...
BTW, the US mains distribution system is different from the European one - this aspect can't be ignored when debating this subject.