Main vs. sub panel for dedicated lines

Different philosophies regarding dedicated lines. Use one line if all your component’s amperage is less than the 20A breaker. The takeaway is no ground loop.
Use more than one line if separating digital and analogue, running high current monoblocks, or running subs. Lighting should be moved to other panel. Certain lights and dimmers will cause hum to audio system.

These circuits should be wired into the same leg (phase) in the service panel. In your current situation, dedicated lines should be run from the panel without the high-current devices. Although both panels will share hot, neutral and ground, the breakers are further away from the appliances that generate noise on the mains.

Two ground rods need to be drilled into mother earth according to your local code. The electrician will know this.

@noromance
8 gauge Romex will not fit 20A receptacle.

4 gang box is good idea if using one line.

@noromance 
Ok, I get it.

Mike, if you're using 10 gauge wire the breakers should be 20A. There's no reason to use one 15 and one 20A. 
If you use 10/2 Romex, you would use two 20A receptacles for your audio.

As stated before, use a subpanel for audio. Main 200A panel will have high-current draw appliances, lighting, and household devices.
Each panel will have an 8' ground rod, check with electrician for code.

@jea48 @mesch
I have a new service panel and a subpanel. When the sub was installed, a second ground rod was added. Two different electricians installed the panels, both said two ground rods were required to meet PA code.

Edit... the 2 panels are near each other on a basement wall.

SQ has been debated, but keep the audio system together on the same leg (phase).

@jea48
Hi Jim, the service I mentioned is the one where you kindly offered advice. Installation was from the drop to a new meter, then inside to a Square D 100A panel, 60A subpanel.

This is a small Philly rowhome where outside the house is pavement. Now don’t freak out, this might be  Philadelphia code; both grounding rods are drilled into the basement cement floor near the rear wall. They’re 3’ apart, sunk into mother earth. I can only see one rod which is wired to the main panel. The 2nd rod is obscured behind my washer/dryer. I will look for the wire.

Question: why are two ground rods used?

I’m guessing the second rod isn’t wired to the subpanel because the main panel is ground, correct?

@jea48 
Sure, I'll check for you. 

Are the two rods connected together by a bare #6 solid copper wire?

I don't recall seeing them connected. Can each rod individually be connected to ground in the main panel?