Actually, a dedicated circuit will only help with providing adequate current. The only way to get rid of distortion from sources in the house is to either move it to the other leg of the service (so if the compressor in the fridge is on leg A, you want to power the amp from a circuit on leg B) or to put in an isolated ground system. In commercial installations where there are sensitive electronics (computers) that can get irritated by noise from things like variable frequency controllers, we put in separate IG panels and even transformers because the noise produced by the drives (and other things, but I'm picking on drives because I'm usually responsible for them being in the building in the first place) affects more than just their own circuit or even their own distribution panel.