Basic electrical questions.

I have read on many occasions various AGON members stating that in effect "separate dedicated circuits alone help decouple components from one another".

From an electical engineering perspective, separate dedicated circuits all connected to the same subpanel would all be in parallel with each other. This means that any spurious artifacts from a component fed back into its dedicated circuit would be superimposed on all other dedicated circuits. Other components power supplies would have to deal with these artifacts, e.g., filter them out. In this regard, this approach is not any better than a single dedicated circuit.

In my own system, I have installed an isolation transformer feeding the subpanel, with separate dedicated lines to each component. To address the issue above, I have put a second isolation transformer on the CD dedicated line to keep its digital hash from contaminating the other components.

This has proved very effective for me, as there is now no difference in the background noise level between the CD player while off, and the CD player playing while muted. If you are contemplating multiple dedicated lines off a single subpanel, I suggest you consider this approach.

Jea48,
I have read Hansen's article, and he does a good job of explaining the sources of disturbances on a household AC line. One has to appreciate well designed audio equipment that operates successfully in such a harsh environment. I do have some issues with his statements on Filters and Fixes (Part 2, pg. 7).

A dedicated line from your service panel to your audio equipment (I call it "star sourcing," similar to star grounding) can do wonders to keep noise and harmonic currents out of your audio equipment. With a dedicated supply, your amplification need only endure the noise from its system mates, rather than the hash from the washer, garage door opener, and furnace.

He recognizes the benefit of multiple dedicated lines with star grounding to reduce ground loops. And he recognizes that multiple dedicated lines by themselves do not prevent noise from one line getting on another. But then he contradicts himself by asserting that dedicated lines to a garage door opener and furnace will not pass their hash over to the dedicated audio line. As long as they are all connected in parallel on a common phase at the service panel, they will all share the same voltage disturbances. You can't have it both ways. I do agree that the length of the connection can attenuate conducted EMI and to that extent some of the crosstalk is reduced, but for short runs it would be minor.

This is why I advocate an iso on the audio subpannel and either a second iso on noisy lines or some conditioning at the componant. In my case the subpanel is adjacent to the audio room and less than 50 ft. from the service panel.

PS, thanks again for your excellent counsel when I designed and implemented this a couple of years ago.

Almarg,
The question of whether to tie the ground to common at the subpanel is an interesting one. I chose to do that and not let the audio system float. There are codes which apply to this question and I will let Jea48 address them if he so chooses.