Where does fine sound begin? Where does it end? Audio enthusiasts have kept asking those questions for ages. As a matter of fact, physical conditions have a considerable impact on the sound quality produced by audio systems. In this, power supply is one of the key factors. In principle, we listen to domestic current modulated by a music signal. This useful signal mixes with modulations or interference from other consumers at your home or even your neighborhood all the time – and this is where sound degradation starts. Countless consumers – in particular, digital devices – and switched-mode power supplies (SMPS) cause heavy distortion in the power system, and their number is still rising. This distortion poses serious problems for your hi-fi components, overlaying your sound like patches of acoustic mist. As the number of hi-fi aficionados running their own power plants is obviously quite low, most devices will almost certainly be fed from a grid under heavy load. So to most of us, this means that sound begins at the power outlet or maybe the fuse box – everything upstream is beyond our control.