I guess it's the mystery of the ages. How should one provide a clean, reliable ground for reference, yet provide, also, a sufficient return path for currents flowing throughout the system? Sometimes GND is a reference, and sometimes it's a current-sink/source. In the end, it's just GND, isn't it?

What priniciples, KAI, would you recommend? How should one set about to avoid contaminating the GND that one needs for reference with the currents that we need to send back to the supply?

RE