There's a small chance that this is an issue with the circuit board. Chips usually have completely separate analog and digital signal grounds. This separation is supposed to continue onto the PCB except for a single point bridging the two. Most PCBs immediately connect it all together instead. This means that one part of an analog circuit might have a signal reference that fluctuates with digital power consumption more than another signal reference. The difference between the two references is a ground loop and it ends up contaminating the analog signals.
You'd think that a few millimeters of a copper trace carrying current would all be the same voltage but it's not. Audio circuit designers need to take great care with this even for low-end equipment.
