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.
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.