strange but true mains quality

thought i would share a recent event , ive had a couple of days off work and started getting round to a few jobs that ive put off forever , one of them being a couple of bad conections in a few light switches , you know the ones that flicker on switch on ! had music playing while i sorted sat down to a cup of tea and the sound of the track playing was by far better than the previous listen ? what had changed ? the switched fuses for the lights in the house were still off with this in my head turned off others leaving basically only the sockets to the hifi which runs on a seperate spur to a sepetate fuse to the rest of the sockets , bloody hell , better sound stage , deeper bass , smoother highs , improvment on all aspects , as i turned each fuse back on the improvment did deminish , my house is fairly new and the mains sub station for the street only a few blocks away , has anyone else had a similar experience is it that the mains supply is very crucial or that RFI from within the house wiring is playing such a part in the reduction of sound quality , i have decent mains cables unswitched sockets to my gear and as ive said a seperate spur would mains conditioning bring back similar improvments , please give it a try and get back to me , mick