Dedicated Line

I need your advice on a dedicated line installation. I look at my breaker box and see the neutral and ground connected to each other by a cross bar.
1. Should i seperate them?
2. Should i build another ground and connect it to dedicated line only?

Your input is really appreciated.
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.
No, don't separate them. In general, the only time that the neutral and ground do not share the same bar is when you're installing a subpanel.

Multiple grounds can be dangerous & are against the electrical codes in most areas. If you have homeowner's insurance, you give the insur. co. a good reason to void any fire or damage claims. You also leave yourself open for liability in case of damage to other's property.
The bars are connected for a reason. Leave them alone. To answer your questions:

1. If you seperate the bars, then each and every circuit breaker in the panel might not trip properly on fault. Self-explanatory as to the danger.

2. No. Only one ground is permitted for the whole house electrical system by code.

Strongly suggested: talk to an electrician or your local BD inspector before you touch anything, regardless of what you read here.
If you have to ask you don't know enough to do this. Hire a competent electrician.

GS5558, I recently had a a new 200 amp service installed and the electrician told me they had to install a backup ground wire from the breaker box to a water pipe in addition to the ground that went to the stake they drove in the ground near where the service comes into my house. Does this violate the "one ground" rule cited above?
Thanks for all input
Herman, no those aren't multiple grounds. They are connected in a star topology so that they all work to enhance the single ground in the system. Not all grounds are created equal; typically the best (ie, lowest impedance) grounds are from a strategic network of copper rods and additional low-impedance routes to the ground, such as cold water pipes.

And I agree with previous posts in that if you have to ask these questions, you should be consulting with an electrician rather than doing it yourself.

Herman, just to add to Sufentanil's post, your electrician was correct. NEC requires a minimum of two earth grounding electrodes. If a metallic incoming water service line is present it shall be one of the two electrodes. For a 200 amp service the ground wire from the neutral/ground bar, in the panel, to the water pipe ground clamp shall be a minimum size of #4 awg copper wire.

As for the ground rods outside, you should have a minimum of two. The rods driven a minimum of 6ft apart from one another. A single bare solid wire run from the ground/neutral bar to the first rod then extended to the second rod continuous unbroken. The two rods are counted as one Grounding Electrode.