I understand the idea is to "isolate" the circuit supporting the stereo / HT from other things which introduce noise. So it's the breaker switch which does the isolating, right? Because at some point it all comes together in the box. IE not possible for "noise" from one circuit to make it back through a common connection point in the box (is this called the bus bar?) and then up into the dedicated stereo breaker / circuit. Am I getting this? I guess I don't understand how an individual breaker isolates that circuit from noise.
A dedicated circuit and breaker won't
totally isolate that circuit from noise. But noise on a circuit can be
reduced by (a) not having noise-producing devices share the circuit, (b) having that circuit on the 120V leg with the least offensive noise-producing equipment and devices, as previously mentioned, and (c) having that circuit closer to the main panel.
A sub panel wouldn't offer any "sonic" advantage over simply tapping into an unused breaker in the main box. It's simply a matter of installation cost and space conservation, right?
A true isolated ground circuit will have it's ground wire connected directly to the panel, rather than shared with other circuits that might provide multiple paths for the ground, as in commercial conduit installations. But this is done for safety reasons. In a commercial hospital, with common grounded conduit, "hospital grade" outlets have their grounds removed from the metal mounting tabs so as not to use the conduit for grounding with it's multiple paths, and instead run a separate ground wire back to the panel.
I would propose that there might be a very small improvement in isolation between circuits if two cables were run back to the main panel, rather than using a subpanel.
If no motors, dimmers or other noise-producing devices were on either of the two circuits, the difference would probably be even less.
Steve
