Just to clear up what that screw actually does. It isn't a "ground loop screw", it's a point of connection between the chassis (safety) ground, and the signal ground.
A device that has a 3-prong electrical connection connects the chassis to the third prong, so any shorts are shunted to ground rather than finding the path there through a person touching it.
RCA cables need their external shield connected to the chassis ground for best noise rejection. But that shield is also used as the signal ground for the audio being carried on the cable.
If everything is working right, there should be no problem tying the two grounds together. But quite often things aren't right. So it worth trading the lesser noise rejection for separating the signal ground from the chassis ground to break a possible ground loop.
XLR cables solve this problem. They have an external shield which should always be connected to the chassis ground, and a separate ground pin for the signal ground. When using an XLR cable, the connected devices should never tie the two grounds together (thus why Axiom has the removable screw).
I'd also like to take a moment to rant about so called "double isolated" electronic equipment with only 2-prong connections. I hate this trend to suppose that what ever design the engineer has come up with will always fail safe, and thus not need a safety ground. It is also not able to provide a true chassis ground for shielding, making any XLR jacks less useful (like in Onkyo's pre-pro line).
EDIT: Of course none of this gets you any closer to solving your problem. I just like to hear myself type sometimes. (It is a nice sound on this Unicomp, buckling spring keyboard.)
Last edited by ClubNeon; 09/07/10 04:53 PM.
