advice on dedicated line

Al,

Here is a white paper of a 2012 seminar by Bill Whitlock.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Check out grounding, starting on page 31.

Note page 35, for those that have to use metallic conduit for the branch circuit wiring. MC cable with an aluminum armor is the best. Conduit runs with loosely randomly installed wires pulled in the conduit is the worst for ground loops.

I would have liked to have seen Bill comment on the effects of multiple dedicated branch circuits sharing the same conduit raceway addressed.

Also check out pages 200 through 212.
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Jim

Very informative thread and a model for how this forum should operate. I am no expert on this but I have to agree that one dedicated line should be plenty for your (and most other) systems. As has been stated, running a single line avoids a host of potential problems associated with multiple lines. I am running a single line to a bank of 4 Porter Port duplex outlets behind my rack. I also turn off my digital playback machine when I'm listening to vinyl--not sure if it makes a difference but there you go. Finally, while there have been a number of suggestions about powerstrips etc. I don't think I see reference to the Environmental Potentials 2050 which acts as both a surge suppressor and noise reducer. It is made for very high technology industrial applications but has found favor among audiophiles as well. I had one installed on my panel along with the dedicated line and my system is dead quiet. Hope this helps.

Great reference, Jim (Jea48), as I'd expect from Mr. Whitlock. And all of the sections you referenced make perfect sense to me. Thanks!

Amazing that it took until the last few years for an explanation and measured verification to finally be presented for "what drives 99% of all ground loops."

I note that rate of change of current is indicated on page 31 as being a significant variable, which reinforces the significance of what I said earlier about not extrapolating results obtained with one amplifier class (i.e. A or AB or D) to other classes.

With respect to the comparison chart on page 35, I wonder what the results would be for the situation that probably exists in many older homes where the metal conduit IS the safety ground connection, for example where older two-prong outlets have been replaced over the years with three-prong outlets, or where a three to two prong adapter is being used, with its ground connected to the cover plate screw. I would guess the results of his test in those situations would be fairly good. I assume, though, that modern code doesn't permit installation of conduit containing only two conductors. Am I correct about that?

I note that the BrickWall I had suggested to Margot is based on the series mode non-MOV technology that is recommended in the paper. And I seem to recall that there may have been some kind of relation between BrickWall and the SurgeX brand he specifically mentions.

Regarding the EP-2050 Dodgealum suggested, having looked at the datasheet and other info on it provided at their website it certainly seems to be a good product, that would be a worthwhile investment in many cases. But as a whole-house protector and noise reducer it appears that it won't do anything to reduce the effects of noise generated within the system, certainly in an application that utilizes a single dedicated line. Also, I note that it lists at $730, plus the cost of professional installation. Also, I would note that the absence of audible noise does not necessarily signify that noise is not a problem. Digital noise has very substantial frequency content far above the audible frequency range, and that high frequency content can have effects within the audible spectrum when introduced into analog circuitry as a result of intermodulation with signal and other effects.

The bottom line would seem to be that given the success many audiophiles achieve with both multiple dedicated line and single dedicated line approaches, and given the system dependency and technical unpredictability of the tradeoff between the possibilities of ground loop issues and inter-component noise coupling, it seems clear to me that there is no one size fits all answer, and in general there is no approach that can be determined to be optimal apart from experimentally.

Best regards,
-- Al

I assume, though, that modern code doesn't permit installation of conduit containing only two conductors. Am I correct about that?
02-11-14: Almarg

Al,

As for NEC 2011 Code, Rigid, IMC (intermediate Metal Conduit), EMT (thin wall), are reconized as an equipment grounding conductor.
Flexible metal conduit 6' or less in length is also acceptable for use as an equipment grounding conductor provided the connectors are Listed for use as equipment grounding means, and the branch circuits is 20 amps or less.

Remember NEC Code is bare minimum. The AHJ (Authority Having Jurisdiction) in the area a person resides may not allow the above metal conduits to be the sole equipment grounding conductor. The AHJ may require an equipment grounding wire to be installed in the conduit with the other branch circuit wires.

The problem I have with using any metal conduit for the equipment ground is the continuity integrity of the couplings and connectors to maintain a good conductive electrical connection over the passage of time. Not to mention how well the conduit installation, fittings tightness, was to begin with.

As for the white paper....
I was glad to see actual testing done for an equipment grounding conductor sharing the same raceway or cable as the current carrying conductors of a branch circuit.

I always thought a voltage could be induced from the current carrying hot and neutral conductor over onto the equipment grounding conductor on a long branch circuit run. We now know why many audio enthusiasts recommended using NM-B cable, (Romex is a Trade name of NM-B), for audio equipment branch circuits.

One thing for sure, conduit runs where the wire is installed after installation is the worst thing for audio. And to repeat what I have said in the past, dedicated branch circuits should not share the same raceway, conduit, with other branch circuits.

For those out there that have to use conduit I suggest MC cable with aluminum armor and solid core conductors. MC can be bought with solid or stranded wire conductors.
MC Cable
http://www.afcweb.com/product-category/mc-metal-clad-cables/
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**Just an added note.
Old homes built before around the middle 1950s and earlier may be wired with old BX cable wiring. Construction of the cable is 2 insulated cloth covered conductors with a steel spiral armor cover around the conductors.
The receptacles back then were the old 2 wire type.

The armor on this BX cable should not be used as an equipment grounding conductor. Not only is the steel armor not an effective ground fault path for fault current, neither is the electrical connection of the BX to box connectors.

NEC 1959 Code required AC/BX cable to have a continuous bonding strip installed under the armor so the cable could be used as an equipment grounding conductor. Just guessing the BX to box connectors were still the same old connectors. By NEC 1962 Grounding type receptacles were required.

Here are a couple of Links.

http://www.inspectorsjournal.com/forum/topic.asp?TOPIC_ID=10144

http://www.dslreports.com/forum/r26797846-using-BX-cable-as-a-ground-

Jim

Jim, thanks for the detailed and nuanced answer. Good stuff!

Best regards,
-- Al