Basic electrical questions.

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.

Zargon -- I did not perceive any contradictions along the lines you describe when I read Hansen's article.

First, although this is not inconsistent with anything you said in your last post, let me say that I don't think his paper addresses at all the question of multiple dedicated lines feeding the different components of an audio system. He addresses having a single dedicated line to the audio system (as he describes for his own system), and additional dedicated lines for other things in the house, such as large appliances and other noise-makers.

Concerning the inconsistencies you perceive in his paper, I think he is simply saying that the amount of noise coupled over to the audio system from non-audio devices would be SIGNIFICANTLY, though obviously not totally, reduced by having those devices and the audio system on separate dedicated lines.

See the reference I made in my previous post to page 4 of Whitlock's paper, for some indications of the inductive impedance of typical heavy gauge power wiring -- it is substantial at frequencies that a lot of noise can be expected to be at, which I think supports my use of the word "significantly" above.

Then there is the separate question of having multiple dedicated lines for the various audio components themselves. Posts by me and several others above have cited considerations which argue both for and against doing that, but your setup seems to have realized the best of all worlds. Way to go!

-- Al

Jea48

Nope. I was talking strickly in regards to the lessend effect of spurious noise equating to the distances of the dedicated line runs. Period.

I’m only a former ELECTRONICS tech, and commercial/industrial electrician, not an engineer or electronic designer, so I speak from my own experience.

My reference to phones for example regarded their charging devices impact on the household’s electrical system, not their common use… as I thought we were speaking of how dedicated lines are more the benefit than common circuits. Albeit, dedicated lines are not the end all be all, which I also pointed to quite early on and prior to many of these following posts. Further, more rechargeable devices can and do add derogatory artifacts into the power delivery.

Even UPCs for personal confusers, if not full wave AC power supplies will additionally infuse DC into the homes power supply. Those $100 Radio Shak ‘crash preventers’ do more harm than good.

Whatever the theory and or reasoning supporting such annoyances, the practical approach to remedy them has always been my tact, for in the end a solution is both what is sought and appreciated. Were I to ever tell some customer that they had a difference of potential across the differing grounds to their varying services, and the resolution for it, I’d be wasting both my time and theirs. Consequently I tend to strive for a more simplified approach when I attempt to convey some aspect which provides benefit. Truth be told here too… in some cases I don’t know the why of it, merely the how and what... for in my former vocation only results were more normally sought.

…and isn’t simple, always best?

My techy side does indeed appreciate many of these insights however, so please don’t take any offense as I underline my sense of things here, as well as others have also fortified in other words that which I promoted at the onset.

Thanks all, for the various links given here as well.