Ground issue

[ctong]

I posted this in another (more appropriate) forum but got no answer. I feel that people here are more knowledgable so I will try it here.

I know this is not exactly a Pass Labs question but the ground issue would also apply to amps.

Ground issue

[Audio_se]

Not sure I understand your question fully.
You want to know why the grounds are separated (isolated)?

I notice the label "AGND" on the circuit to the left in the schematic.

One should pay same attention to ground as to signals and power supply. Remember that current flows in closed paths.
A better name for ground would be return current.
So ground is not just something you can connect to what you want.
A ground wire will have voltage drop, crosstalk, inductance, .... as any other wire.

This is the reason to separate grounds here.
Yoy don't want the analog ground to be affected by currents flowing from the digital circuits. This would corrupt the analog ground which is the reference (zero volt) for audio signals.

[ctong]

I am bothered by the fragmentation of the analog ground in the 555es. In the 777es all the A grounds are connected and is separated from the D ground by a 2.2ohm resistor. I am going to experiment several options and see which sounds the best.