Sony MHC-ZX70DVD System "humming sound stereo" Questions

...stereo speakers sound garbage ! there's high and low frequency wiring options and neither of them produce good quality sound. the low frequency (european) setting is so muffled its impossible to make ...

...humming sound through the speakers. It doesn't change with the volume, but does disappear when there's no volume at all. I've tried unplugging everything and even using different speakers, but still ...