Lior, I have always been told to connect the shield only to the source side. If you look at some commercial interconnects they have directional arrows on them, that is why. You don't want the interconnects grounded to the Crack's chassis, that is why the RCA jacks are insulated and isolated from the top plate. For headphone cable you would connect the shield to the ground of the trs, xlr or whatever you use to terminate the cable. If you connect the shield to the destination, (Crack or headphones), you will get a bunch of hum. Hope this helps.
Cheers,
Shawn
