I have an audio application scenario here. The Idea is to power a device (that later produces sound) with USB.
Unfortunately, I have massive static and what sounds like pink (Brownian) noise on GND. I also have a lot of static and other artifacts on the +5V lead, but I figured I can use a low-dropout voltage regulator to get a nice, smooth +3V out of it.
But how do I filter out GND?
Right now, I was experimenting with all sorts of low-pass and high-pass filters, constructed from caps and resistors. The caps, however, introduce artifacts themselves, it it's like two steps ahead, one step back.