Main vs. sub panel for dedicated lines

I am unclear as to what you are doing with this second home. If it really is a second home it would have its own service and panel. If you are running it off of your main panel then yes it would be a sub panel situation. If the listening room is in this second building then you would run the ONE dedicated listening room line to this sub panel.

Main thing is there be one dedicated line, and everything in the system uses this one line. All the lights and other outlets for accessories, you can run as many lines as you want for those. The system however, it all goes on one line.

The relevant comment from Michael Fremer starts at 15:50  https://youtu.be/H07NpWk_Xf8?t=950

One line. 10 or 8 gauge. 20amp breaker. 4 gang outlet. Distribution box.

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.

@lowrider57 Yeah. I should have been more clear. That’s why I said 10 or 8. I run 8 gauge into a L6-20R which then feeds a 4 gang box.