Shared ground between MIC and line-out ?

[samyrabih]

Hi !
The Audio Adapter PCBdisplays a warning about NEVER connecting VGND and GND.

But does it apply to line-out pins ?

(I'm currently creating an Teensy-based audio guestbook with old phones and the wires between the main element of the phone and the handset contains only 3 cables, so if I want to avoid replacing the wire by a 4-cable one, it should be useful to be able to share grounds).

If it is a bad idea to share grounds between line-out and MIC, please tell me.

If it generates bad record quality, you can tell me too

Thanks

[samyrabih]

Self analysis : ground is shared between the GND near MIC, and the line-out GND

But not between MIC's GND and the GND near VOL. So next step is to test recording and reading audio with shared ground