Bridging digital and analog grounds with cap

[burningman]

What benefits are there to connecting digital and analog grounds through a .1uf cap. I have seen this in quite a few designs. Thanks

[Processaurus]

Do you have a schematic as an example?  That just doesn't work, ground needs to be a direct (or through a resistor or diode in special cases) connection, whether digital or analog, as DC current needs to come to and from the power supply to make electronics work, and caps block DC.  Having a cap in the path would make it work for about a millisecond, until the cap charged up, and then it would block the DC on one side from getting to the other, and it looks like an open circuit to the DC.

I have seen some enclosures grounded to circuit ground through caps (Line 6 and some newer Boss digital pedals) for some reason, this allows RF and audio frequency noise to be shunted to ground, though I'm not sure what they gain by stopping the DC component.

There is one method of wiring studios balanced connections where shield sleeves of balanced lines are grounded on one end for real, and rather than lifting the other end completely, the other end through a .1 cap, which prevents a ground loop, but allows RF and audio frequency noise through.

[burningman]

Thanks for the explanation. I was looking at the traces on the power supply of the sdd3000 and mistook ceramic bypass capacitor for a connection between the two grounds. That being said, do you or anyone else know where the single grounding point for digital and analog grounds is on this unit? Thanks.