Timtim,
As has been said, it is essentially an absolute must to have a ground rod at the service entrance, that serves ALL runs. For reasons of code compliance, effective circuit breaker operation, lightning protection, etc.
No one in this thread has advocated independent ground rods for each line that is run to the system. And I think that Jea has effectively made the case that having even a single ground rod dedicated to the system is pointless, as well.
The question of tying the dedicated ground runs (not rods) together at the system is a little less clear cut. As I indicated earlier, there is both potential upside to keeping them separate (improved isolation) and potential downside (offset voltages between chassis causing noise currents to flow in common with signal returns).
That downside would pretty much be negated, I think, in the case of a system that had balanced interconnects. But most systems have some or all of their interfaces single-ended. For those cases, I am not in a position to offer generally applicable guidance as to whether the upside or downside is more likely to prevail. It could be that trial and error is the only way to tell in a particular case. And as I said earlier, a more ideal solution would be to make use of isolation transformers as discussed in the other thread I referenced. It seems pretty widely agreed that both the isolation they provide and the filtering that results from their limited bandwidth make them a very effective approach.
Regards,
-- Al |
OK ... Timtim back with this thread. I was going on advice from a tech at PS Audio about the dedicated grounds. Personally, I don't really care which way I do it, as long as it works as well as possible.
Running different dedicated lines to keep my digital and analogue equipment separated sounds like a no brainer, but if the grounds are tied together for these lines, are they truly separated ? Then again, noise usually comes in on the neutral leg anyway.
Lastly, I can't see ANY good at all from running independant ground rods for each line, then grounding gain at the panel. That sounds like a ground loop just waiting to happen. |
I provided the link to show what can happen if the equipment ground for a branch circuit was connected to an earth ground electrode ONLY.[emphasis added] Yes, I agree completely, that would be a definite no-no. Thanks for the good references! Regards, -- Al |
Stray voltage
Interesting paper, but it doesn't seem to be particularly relevant, and I don't think it makes its case completely. His theme seems to be that cost reduction measures taken by utility companies cause ac return paths to power company equipment to be partially through the earth, instead of entirely through their wires, and that that is somehow harmful to people and animals. But I didn't see any explanation of how that current flow might result in significant voltage difference across any individual animal or person, other than brief mention of in-ground swimming pools (and I'd want to see more evidence or quantitative explanation before concluding that he is right in that case).
In any event, I don't think his paper has relevance to connecting an audio system ac safety ground to earth, when a very nearby connection to earth of that same ac ground would exist at the service panel.
12-24-08: Almarg Al, I provided the link to show what can happen if the equipment ground for a branch circuit was connected to an earth ground electrode only. In this case any ground-fault current would have to travel through the earth to return to the source. The path/s taken would depend on the least resistive path/s available. Depending where the isolated ground rod is driven into the earth with respect to the proximity of other earth electrodes that are connected to the grounded conductor of the source, the utility transformer. Possible ground-fault path/s back to the source? * Through the earth to the grounding electrode system of the electrical service panel of the house that the branch circuit was fed from. * Through the earth to the grounding electrode system of the neighbors house next door to their electrical panel then on out through the service entrance conductors to the utility transformer. * Through the earth to the grounding electrode of the utility transformer where the primary winding and secondary winding grounded conductors are bonded together and connected to earth. As you can see there are multiple paths the ground-fault current could take to complete the circuit back to the source. A poor conductive path I might add. |
Timtim,
I am thinking of using an input line reactor to a seperate sub panal I have planned for my audio room.
I use them alot in my trade to stop unwanted electrical issues too and from VFD's. I do not think anyone in audio has tried this but I think it will help with power and noise issues.
I will tell you how it go's later.
Has anyone tried this? |
The earth shall not be considered as an effective ground-fault current path.
From 2005 NEC 250.4 (A) 5 True, but the presence of such a path will do no harm as long as the proper path is also present, at the service entrance (that proper path presenting a much lower impedance to fault current than the extraneous path, as diagrammed in Whitlock's paper). The earth does not have some magical mystical power that sucks AC noise from our audio systems. Agreed. As I admitted, you are likely correct that a ground rod near the system would accomplish nothing. More and more audio equipment manufacturers are building their equipment with double insulated AC power wiring thus eliminating the need for an equipment ground. They are finding the use of an equipment ground causes more problems than the added cost of the double insulated power wiring. That's interesting; maybe one of the problems they are finding is exactly what I was describing -- voltage offsets in safety grounds causing noise currents to flow through signal return paths, a problem which would be eliminated if signal ground and ac safety ground were not both tied to chassis. Stray voltage Interesting paper, but it doesn't seem to be particularly relevant, and I don't think it makes its case completely. His theme seems to be that cost reduction measures taken by utility companies cause ac return paths to power company equipment to be partially through the earth, instead of entirely through their wires, and that that is somehow harmful to people and animals. But I didn't see any explanation of how that current flow might result in significant voltage difference across any individual animal or person, other than brief mention of in-ground swimming pools (and I'd want to see more evidence or quantitative explanation before concluding that he is right in that case). In any event, I don't think his paper has relevance to connecting an audio system ac safety ground to earth, when a very nearby connection to earth of that same ac ground would exist at the service panel. Thanks for the interesting read, though! Best for the holidays and new year, -- Al |
The earth shall not be considered as an effective ground-fault current path. From 2005 NEC 250.4 (A) 5 The earth does not have some magical mystical power that sucks AC noise from our audio systems. More and more audio equipment manufacturers are building their equipment with double insulated AC power wiring thus eliminating the need for an equipment ground. They are finding the use of an equipment ground causes more problems than the added cost of the double insulated power wiring. Stray voltage. |
I agree with all of the excellent cautionary statements that have been made. I want to clarify that the suggestions in my previous post (the third post in this thread) did not mean to suggest anything contrary to these cautions. I assume that there is and will continue to be a bond between ac neutral, safety ground, and earth ground at the main entrance of power into the house, near the breaker panel. For all existing runs, and for the new ones that may be added. The earth ground is essential for lightning protection, and the bonding of ac neutral and safety ground at that physical location is essential for effective circuit breaker operation, as the paper Jea48 linked to makes clear. And, yes, it seems likely that not having outlet receptacles may be a code violation. But to restate the point I was trying to make: The downside of having dedicated runs to different parts of the system is increased voltage differential between the chassis of the different components, particularly at high frequencies, which can result in noise currents flowing through the same cable shields as signal return currents, thereby effectively summing the noise into the signal (the very thing that having multiple ac runs is intended to improve). Connecting the grounds of the different runs together, near the system, will minimize those voltage differences. Jea may very well be correct that tying that local system ground to an earth rod will not accomplish anything, but I don't envision that it would have any negative effects either (in terms of either safety or performance). A better approach all around, though, may be to utilize isolation transformers, as described by Zargon in this thread: http://forum.audiogon.com/cgi-bin/fr.pl?htech&1228780109Regards, -- Al |
timtim
A word of caution.
What you are doing may not be legal. You must bond all grounds. Even in isolated outlets you still bond the all ground wires, thats why there are 4 wires for isolated outlets and not 3 wires like standard house wiring. You will not be able to that the way you are doing it. You could have issues with the insurance company if your house gets set on fire from those electriacal feeds. You may be able to cut the end off a cord and terminate it in the wall. Electical romex feeds are not meant to go diractly to any source equipment.
Check local electrical codes, because what you can do in one city or state does not mean you can't do it in another. |
I don`t know about all the tech talk above but, a company called "Tributaries" known for cables, IC`s etc. also makes "Audiophile" grade house wireing, Romax, better than the stuff at Big Box Lumber etc. I had a 20' run installed as a seperate line feeding my monoblocks.
and it looks purdy too, bright orange so your friends know....! |
Can't comment on the technical issues, but I would check w the local building inspector about hard-wiring the items w/o wall receptacles. It probably does not meet code and could be an issue w your insurance co. if (god forbid) you ever have a fire. YMMV. |
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My instinct would be to use ONE copper ground rod, close to the system, with the grounds of the three Romex runs coming together at one and only one physical point, at that ground rod.
As you obviously realize, the upside of dedicated runs that are separate for digital and analog components is reduced cross-coupling of digital noise into the analog components. The downside is possible voltage offsets between the chassis (and consequently the signal grounds) of the different components in the system, particularly at high frequencies (such as typical noise frequencies), due to the inductance in the wiring. If your components are unbalanced, meaning that they use single-ended interconnects, these voltage offsets result in extraneous current flow in the shields of those interconnects, that is in common with the current flow of signal return paths.
So to minimize that downside, you want to have the chassis and consequently the signal grounds of all of the components as electrically common as possible, with as little inductance between them as possible. DC resistance will probably be sufficiently low regardless of what you do; the concern is with inductance, that can dramatically increase ground run impedance at noise frequencies.
I think that using one ground rod as I suggested will accomplish that. As long as the grounds are tied together at only one point, so that no ground loops exist, there is no reason to "keep the grounds separated." And having three separate rods in relatively close proximity doesn't really keep them separate anyway.
Regards,
-- Al |
You are taking this way too seriously.
I have 3 dedicated lines all with 10 gauge going direct to the circuit panel. On the other end are Wattgate outlets.
Wiring direct will be a pain later down the road as your system changes , and it will look crappy and will not provide any sonic benifits.
Too many grounds and you will induce humm.
However, lifting the ground on your Digital might improve things. |
