Glen: As you know, i'm not an electrician, nor do i play one on TV or Audiogon : )
I guess i should have clarified that each circuit should have its' own hot, neutral and ground to minimize series resistance and negate any possibility of wire saturation. Sharing neutrals would increase cross-talk between circuits and could result in the situation that you described. This would also cut down on the noise isolation characteristics that we are trying to achieve by going to dedicated / isolated lines. I guess that i took for granted that one would know enough to do make sure that this was done, but i guess i took too much for granted. Thank you for bringing this up.
As to your comments about common neutrals and electrical fires, i just read an article about this. It seems that the massive influx of switching power supplies, digital gear, etc... is playing major havoc with house wiring and the power companies nowadays. I am thinking that there will have to be some major changes to the various local and national power and wiring codes in the near future to try and alleviate these and other potential problems. Have you seen / read / experienced any problems with this type of situation ?
Natalie / Glen: I think that your experiences are more the exception than the norm when it comes to dedicated lines and noise reduction. While i do agree that dedicated lines will lower the noise being fed into the system, i still think / have experienced major amounts of noise being pumped in on dedicated lines. If one is in a heavily populated area and / or has any type of industry nearby, there is nothing short of heavy filtering that will remove / negate the noise that is coming down the line. With that in mind, I have to ask: "what makes you think that running separate breakers / lines from the other circuits in your house would remove all of the other outside interference that is already present on the mains" ?
No matter how many lines you have hooked up or parallel paths the noise can take, it will go wherever the current is drawn. If your system is drawing current, i'll bet that there is noise on the line feeding it. That is, unless you are operating from a bank of batteries and a high powered inverter ( i need not mention names here : )
As mentioned in another current AC noise thread here on Agon, one could / should check into just how "quiet" their AC is by using a "Noise Sniffer". I have actually witnessed a name brand "Power Line Conditioner" / "Noise Filter" introduce MORE noise into the system than if a device was plugged directly into the wall. The "Noise Sniffer" can actually help you to track down sources of noise within your own house. It helped me to identify what was "sneaking through" an otherwise "excellent" PLC.
Drubin: My comments are based on the fact that many "isolated grounds" are installed in areas far away from where the ground that is connected to the main breaker box is installed. As such, there is the potential for a vast difference in ground conductivity to exist. In such a case, the difference in conductivity will result in a voltage potential being placed on the chassis of anything that is connected to either ground IF there is a connection made between the two grounds. These voltages can be quite high, resulting in noise being generated, ground loops, hum, etc... Under specific conditions, such a combo could become lethal. THAT is why it is "illegal" in most places to have multiple grounds.
To reduce the potential for such a situation to exist AND keep your dedicated / isolated ground, one should install a ground rod as close as possible to where the mains are grounded. While this may raise series resistance to ground a little bit in terms of the distance that it must travel from your audio system, one can get around this by running a heavier gauge wire. What this accomplishes is that both grounds ( the mains and the dedicated outlets ) share common ground conductivity. This minimizes the difference in ground potential between the two, yet allows you to keep them separate. If a building inspector "wanders by", he would probably throw a fit and tell you that the two grounds need to be tied together, which really isn't a big deal either. Since they would be joined right at the point of Earth entry, cross-talk from the mains and dedicated lines should be shunted anyhow. It is only when circuits share a common ground that is long in length or resistive before being shunted to Earth that noise becomes a problem in most cases.
While i'm on the subject of grounding, i would suggest that once everything is installed and verified to be working properly, i would take steps to waterproof / insulate your ground rod / wire termination. Since this is going to take place at ground level and probably outdoors, it will be exposed to all of the elements i.e. rain, dew, possibly snow, etc... As such, a corroded ground is just as bad as no ground in my book. Just remember that whatever you use to seal up this connection should be easily removable as it might have to be taken off for system maintenance, etc...
Also, you might have gathered that one should install good sized conduit if doing this from scratch. This would allow you to pull as much wire as needed now and leave room to move in terms of "wiring upgrades" or additional circuits in the future. Better and cheaper to do it "right" the first time than to have regrets later.
If i have made any mistakes in this, PLEASE take the time to correct me. As i stated, i'm not an electrician and as we all know, AC can be extremely dangerous. Not only do i want to learn what will work "best", i want it to be done in what is the safest and ( hopefully ) most legal manner possible. Hope this clarifies a few things and helps some of you out. Sean
>
I guess i should have clarified that each circuit should have its' own hot, neutral and ground to minimize series resistance and negate any possibility of wire saturation. Sharing neutrals would increase cross-talk between circuits and could result in the situation that you described. This would also cut down on the noise isolation characteristics that we are trying to achieve by going to dedicated / isolated lines. I guess that i took for granted that one would know enough to do make sure that this was done, but i guess i took too much for granted. Thank you for bringing this up.
As to your comments about common neutrals and electrical fires, i just read an article about this. It seems that the massive influx of switching power supplies, digital gear, etc... is playing major havoc with house wiring and the power companies nowadays. I am thinking that there will have to be some major changes to the various local and national power and wiring codes in the near future to try and alleviate these and other potential problems. Have you seen / read / experienced any problems with this type of situation ?
Natalie / Glen: I think that your experiences are more the exception than the norm when it comes to dedicated lines and noise reduction. While i do agree that dedicated lines will lower the noise being fed into the system, i still think / have experienced major amounts of noise being pumped in on dedicated lines. If one is in a heavily populated area and / or has any type of industry nearby, there is nothing short of heavy filtering that will remove / negate the noise that is coming down the line. With that in mind, I have to ask: "what makes you think that running separate breakers / lines from the other circuits in your house would remove all of the other outside interference that is already present on the mains" ?
No matter how many lines you have hooked up or parallel paths the noise can take, it will go wherever the current is drawn. If your system is drawing current, i'll bet that there is noise on the line feeding it. That is, unless you are operating from a bank of batteries and a high powered inverter ( i need not mention names here : )
As mentioned in another current AC noise thread here on Agon, one could / should check into just how "quiet" their AC is by using a "Noise Sniffer". I have actually witnessed a name brand "Power Line Conditioner" / "Noise Filter" introduce MORE noise into the system than if a device was plugged directly into the wall. The "Noise Sniffer" can actually help you to track down sources of noise within your own house. It helped me to identify what was "sneaking through" an otherwise "excellent" PLC.
Drubin: My comments are based on the fact that many "isolated grounds" are installed in areas far away from where the ground that is connected to the main breaker box is installed. As such, there is the potential for a vast difference in ground conductivity to exist. In such a case, the difference in conductivity will result in a voltage potential being placed on the chassis of anything that is connected to either ground IF there is a connection made between the two grounds. These voltages can be quite high, resulting in noise being generated, ground loops, hum, etc... Under specific conditions, such a combo could become lethal. THAT is why it is "illegal" in most places to have multiple grounds.
To reduce the potential for such a situation to exist AND keep your dedicated / isolated ground, one should install a ground rod as close as possible to where the mains are grounded. While this may raise series resistance to ground a little bit in terms of the distance that it must travel from your audio system, one can get around this by running a heavier gauge wire. What this accomplishes is that both grounds ( the mains and the dedicated outlets ) share common ground conductivity. This minimizes the difference in ground potential between the two, yet allows you to keep them separate. If a building inspector "wanders by", he would probably throw a fit and tell you that the two grounds need to be tied together, which really isn't a big deal either. Since they would be joined right at the point of Earth entry, cross-talk from the mains and dedicated lines should be shunted anyhow. It is only when circuits share a common ground that is long in length or resistive before being shunted to Earth that noise becomes a problem in most cases.
While i'm on the subject of grounding, i would suggest that once everything is installed and verified to be working properly, i would take steps to waterproof / insulate your ground rod / wire termination. Since this is going to take place at ground level and probably outdoors, it will be exposed to all of the elements i.e. rain, dew, possibly snow, etc... As such, a corroded ground is just as bad as no ground in my book. Just remember that whatever you use to seal up this connection should be easily removable as it might have to be taken off for system maintenance, etc...
Also, you might have gathered that one should install good sized conduit if doing this from scratch. This would allow you to pull as much wire as needed now and leave room to move in terms of "wiring upgrades" or additional circuits in the future. Better and cheaper to do it "right" the first time than to have regrets later.
If i have made any mistakes in this, PLEASE take the time to correct me. As i stated, i'm not an electrician and as we all know, AC can be extremely dangerous. Not only do i want to learn what will work "best", i want it to be done in what is the safest and ( hopefully ) most legal manner possible. Hope this clarifies a few things and helps some of you out. Sean
>
