The better the grounding schemes of the individual components in your system (and assuming your house wiring is to code), the more you will find that such grounding boxes have less effect if any at all.
A properly grounded bit of audio electronics will have its chassis grounded by the AC cord, but its electronics will not be tied directly to that chassis. In this way the chassis can provide shielding without opening the component to ground loops. The sound is more 3D and the background noise lower, as compared the same circuit that lacks proper grounding.
A properly grounded bit of audio electronics will have its chassis grounded by the AC cord, but its electronics will not be tied directly to that chassis. In this way the chassis can provide shielding without opening the component to ground loops. The sound is more 3D and the background noise lower, as compared the same circuit that lacks proper grounding.