Earth (isolated) ground vs. wall outlet ground.

@erik_squires Indeed.

Great answers thanks.  But what of the grounding posts on much equipment, including grounding blocks and common grounding of equipment I have seen mentioned?  Are these only for systems with poor electrical grounding?

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.

If you have hum in your system it probably is a ground issue. You should consult a licensed electrician. Multiple ground points can create voltage differential... bad. There are options if you are having noise problems, which often show up in older installations where multiple neutrals are tied together for expediency. Electricians are familiar with grounding problems, they can play havoc with computers. Maybe not so familiar with audiophile equipment, but many of the same issues. The ground stud is there for your convenience, Some of the older 2 wire components ground through the shield of the interconnect. When that is not sufficient, or an incomplete circuit, the ground stud, or a cover screw, can be of use. Most equipment in the phono side benefits from a physical ground, BTW, if you have hum from an older 2 wire turntable, turn the plug 180 in the outlet, realigning the neutral. Be careful, you can do worse than hurt yourself (or someone else). Consult a pro, and don't mess with the panel.

Great answers thanks. But what of the grounding posts on much equipment, including grounding blocks and common grounding of equipment I have seen mentioned? Are these only for systems with poor electrical grounding?

The electrical ground that comes from the service panel is for safety. Millivolts of difference in a ground potential won’t affect the safety features.

The problem with a lot of audio equipment is it ends up with multiple "ground" references, with some or no relationship to the outlet, and the transformer center taps fighting to be "correct."

The worst such problems often come from PC’s which have a very different "ground" for the electrical interconnects than the power plug. This is why proper grounding may become an issue. It has nothing to do with the quality of the wiring in the home, and yet, the quality of the ground in your home is important for life safety.

IMHO, the best configuration for high quality audio is to float the signals with no relationship to the earth/safety ground. My Luxman integrated does not use the AC ground at all. This is probably breaking US/UL regulations but as a result what I do not have is a ground loop. :D

You may notice some DAC makers make a point of touting the incoming copper connectors (USB and coax) are galvanically isolated.  Sadly, not all DACs do this.