The ground and neutral should always be bonded together at the bus bar of your breaker box according to electric code requirements in most jurisdictions in the U.S. From what I have learned (and I'm not an electrician, just another audio hobbiest), the value of a dedicated line is that the neutral and ground not be connected anywhere except where they are bonded in the breaker box, that the ground wire not be connected to other outlets and equipment other than the equipment plugged into the outlet served by this dedicated line, and that you have a continuous run of wire from the breaker box to your outlet (to the extent you can accomplish this given distances). At the breaker box bus bar, only one wire should be lugged down in each space in order to ensure the tightest and most durable connection. If you have two wires sharing the same lug spot, it would be a good idea to give each its own spot on the bus if you have openings available.
If you use a silver paste contact enhancer elsewhere in your audio system (such as Walker Audio E-SST), these connections are another place where improvement will be obtained by using the contact enhancer. If nothing else, its good periodically to make sure all these connections are clean and tight. Caveate: all of this assumes you know your way around an electrical panel and how to do this safely. Otherwise, get a qualified electrician.
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