Basic electrical questions.

You will find a good part of the following thread to be relevant to your questions:

http://forum.audiogon.com/cgi-bin/fr.pl?ymisc&1228674146

As you will read there, recent (but not some older) 20 amp receptacles have a T-shaped slot for the neutral prong, which allows them to accept both 15 amp and 20 amp plugs.

I agree with LK that I would not feel comfortable plugging directly into the wall. I would want the protection of a surge suppressor, that is dedicated to the audio system.

I'm uncertain about the concept of having multiple dedicated lines for different parts of the system. I would be concerned that voltage offsets could be introduced between the grounds of the different components, which could lead to ground loop noise. Same goes for having parts of the system on a surge suppressor, and other parts of the system on a different suppressor or no suppressor -- the result would be some degree of isolation between the ac grounds of the different components in the system, at least at high frequencies, due to inductive filtering in the suppressors, and inductance in the house wiring, which might cause ground loop issues.

The need for a line conditioner (as opposed to a simple surge suppressor) will, as LK indicated, depend on the quality of your ac supply, and also on the designs of the power supplies in your particular components. There might be less need for one if you have a dedicated line, as you stated (depending on whether the significant noise sources are elsewhere in your house, or if the noise is present on the wires that come into your house). Other people's experiences can initially point you in what are hopefully promising directions, but a conclusive determination can only result from trial and error, imho.

Regards,
-- Al

Can someone offer either a technical explanation, or at least some persuasive anecdotal evidence, to explain the claim that running multiple dedicated lines to the different components of a single system is beneficial. As I indicated in my earlier post:

"I'm uncertain about the concept of having multiple dedicated lines for different parts of the system. I would be concerned that voltage offsets could be introduced between the grounds of the different components, which could lead to ground loop noise. Same goes for having parts of the system on a surge suppressor, and other parts of the system on a different suppressor or no suppressor -- the result would be some degree of isolation between the ac grounds of the different components in the system, at least at high frequencies, due to inductive filtering in the suppressors, and inductance in the house wiring, which might cause ground loop issues."

Regards,
-- Al

Jea48 -- That was an excellent paper; thanks!

However, it does not really address my question, which as you appear to realize was about having MULTIPLE dedicated lines powering different parts of the same audio system. The author describes his own setup, which has a single dedicated line running to a receptacle into which he plugs a diy power strip + switch. He does provide some good information as to connection order, such as connecting the power amp to the end of the strip closest to the incoming ac.

I understand your point about decoupling the power supplies of each component from the supplies of the other components, particularly to isolate digital components from analog components. But I'm uncertain how to reconcile that with the concerns I expressed, about ground loops and the possibility of having ac ground points that are offset from each other at least at high frequencies.

When I get a chance I'll try to take a look at the AA archives you mentioned.

Thanks again,
-- Al

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.

I would think that the inductance of the one or two hundred feet of round-trip wiring that is involved is likely to be significant at noise frequencies.

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.

Interesting approach! The combination of isolation and bandwidth limiting that the transformers provide would overcome the concerns I expressed about ground loop noise, while still achieving the decoupling benefits of multiple dedicated lines. Excellent! Do you tie the system to a (single) earth ground at some point, though, to keep it from floating relative to earth?

Regards,
-- Al

Shadorne and Jea48 -- I went through the Bill Whitlock paper and presentation you linked to -- really super!!! He's absolutely right when he says these issues are not adequately addressed (or addressed at all) in EE curricula, and even EE's often don't know the difference between a ground loop and a fruit loop. :)

Shadorne -- thanks very much for the compliments. As someone with a digital design background, and who builds his own pc's, I agree 1000% that pc's are particularly proficient noise generators, due primarily to the fast edge speeds (rise and fall times) that are present on the innumerable digital signals running around in them, as well as to the large currents that can be change value very quickly as a result of fluctuating demands on the cpu and other devices.

Whitlock very persuasively supports what you said about high impedance shields, in single-ended interconnects, saying that they are typically one of the most major contributors to noise problems. He makes the point that ground offsets and resulting noise are inevitable (although they can be minimized), but it is the resistance of the shields of single-ended interconnects where that noise typically gets introduced into the signal path to the greatest extent. Therefore single-ended interconnects should be as short as possible, and selected for the lowest possible shield resistance.

Blindjim -- Re signal attenuation per unit length of cables, you are probably thinking of video or rf transmission lines, where both the cable impedance and the signal frequencies are well defined and controlled. I don't think that the attenuation is determinable in a meaningful way for noise components that are present at many unknown frequencies and are being conducted through power wiring that has poorly defined and controlled high frequency characteristics. But see page 4 of the reference below (one of those that Shadorne and Jea48 provided) for some rough indications of the impedance of typical power wiring.

For those who don't have time to go through the 140 pages or so of these two references, I'd suggest at least looking at the following pages of this link:

http://www.jensen-transformers.com/an/generic%20seminar.pdf

Page 12: "how the noise gets in"

P. 14: "solutions"

P. 20: "choosing cables"

P. 21: "a checklist" -- especially good!

P. 27: "always ground shield at driver (at least)"

P. 28: "unbalanced to balanced interfaces" (if applicable)

P. 40: "Many of the benefits often ascribed to power treatment schemes are simply due to plugging all system equipment into the same power strip or dedicated branch circuit. For obvious reasons, this is always a good idea"

P. 40: "surge suppressor cautions" (they can do much more harm than good if used improperly)

Thanks again,
-- Al

Cellphones and cordless phones emit far higher frequencies than the frequency components of the digital hash, other component-induced noise, and power line noise that we have been speaking of. I believe cellphones operate in the range of 800 to 1900 MHz or so, while cordless phones are around 2400 MHz. Audio equipment seems unlikely to have any detectable sensitivity to frequencies above perhaps a few ten's of MHz, and perhaps much less than that.

Also, as you appear to realize, these kinds of issues are likely to be dependent on location, house wiring, system components, system interconnections and setup, and listener.

Regards,
-- Al

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