Interesting topic. I've been asking myself these same questions for years. My old sixty three year small house has all two prong outlets from an old fuse panel. The only ground is through the wall to the ground rod(I assume) buried to this panel. Always worried me if my system(somewhat expensive) would be protected, even with a Furman Power Conditioner/protector. Some years ago I installed a "ground box" from a certain manufacturer in the UK, with grounds going to each piece of audio gear. Never trusted this set-up and the sound quality was no better. Got rid of that and installed a dedicated ground rod just outside the wall near my systems outlet and ran a heavy gauge copper cable to that outlet only New hospital grade three prong. This set-up is working great. Am I wrong to think that I will be protected from a lightning strike or such? I am not an Electrician.
Earth (isolated) ground vs. wall outlet ground.
Looking on my 200amp main panel I notice that the neutral (white) wire bus and the ground (bare copper) bus have continuity. Wouldn’t it be better if my interconnected rig had it’s own earth ground thereby isolating it from feedback from the neutral wires? If not (NEC rules, Ott’s Grounding Myths, etc.) why is there a ground lug on some of my pieces? Surely it’s not there for decoration. I can’t imagine a manufacturer adding a useless item (adding cost) in a hidden place if it didn’t have specific function. All my pieces are connected by balanced XLRs (except the speakers) and the balanced XLR has unified grounds. Inquiring (and in my case sometimes simple) minds what to know.....