Questions about grounding

[kraal]

Hi,

I have three separated ground plane on my board: signal, power and digital (all connected in a single point). I have two questions:

1) I have a set of logical gates (connected to digital ground) that are used to open/close the gate of a mosfet. The drain is connected to the power supply. When the gate is high, then current is provided to a relay. The relay is connected to ground. Should the relay be connected to power ground or to digital ground ?

2) the relay is a dpdt that switches on/off a LED on one of the two poles. So far I connected this LED to the power ground is it correct or should I connect it somewhere else (direct to DC jack negative pin) ?

Thanks you for your help !

[GibsonGM]

For both, I personally would connect them as close to the power supply as possible (your 'power ground').  You just want them away from the audio path as much as you can place them, to avoid switching noise...