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In Reply to: RE: interesting posted by Ted Smith on June 29, 2007 at 07:28:20
Ahh! It all makes sense now, thanks for the explanation. For some reason I started thinking this shared neutral was an epidemic or something, and had begun to question my own sanity.
Re the shared earth: I think this might even be THE way to go for RFI immunity but I would assume the conduit is a code requirement for this type of installation. Does the code specify a conduit material/conductivity? If you could get away with using a conduit material that has minimal interaction with the signal itself then this way sounds nearly perfect to me. Obviously you will still have to be careful about starring out from the honkin earth at the equipment end of the run....but I like it.
Follow Ups:
Howdy
I know people are worried about the material in the conduit, but I wouldn't stress about it. The difference from standard wiring to dedicated lines is sooo big in my experience that I'm skeptical about the additional gains to be had with other conduits. I suspect that the specs are more about robustness when nails are accidentally driven into it, etc. than conductivity... But perhaps the conductivity is part of code too, that's why I hire an electrician :)
-Ted
Howdy Ted,
I kind of geek out on things sometimes, so I'll understand if you get bored and quit replying :)
In the end I would definitely approach a licensed pro to get the job done, but I also expect I'll have some design already either written down or in my head that I would expect the installer to closely follow while offering advice on how to pull it into code conforming configuration.
I really like the single ground idea and I bet it sounds really good that way too. I think the only way that's gonna approach satisfying code around here where I live is with conduit. If I could get away with PVC for the conduit material or somthing easily accessible like that I think that would satisfy my needs. Do you happen to know what your conduit material is? I suspect most are metallic and grounded but I'm sure no electrician.
Regarding the questionable signifigance of this particular detail: the skeptic in me always doubts and is stingy with the money but the eccentric audiophile says nothing is too good for my precious. Those two are constantly going at it.
I have a nagging voce telling me maybe there is a concern under the right conditions. I think what would worry me most is high current lines. I know my (class AB) amps don't have any real regulation on the final stages rails and so will be fairly susceptible to line noise and I'd rather avoid power conditioning and filtering as much as possible.
Bear with me I came up with a hybrid solution for the forums consideration. I think this hybrid approach could allow for taking advantage of the benefits of your approach but avoid ptential power quality pitfalls where they are expected to be a concern. For example I like your solution for low power devices with very little ac line current demand because low power devices, ie low ac current draw devices, should minimize this potential coupling between ferrous conduit and service conductors current and you still get the added RF immunity a single honkin ground offers. Then for higher powered devices like monoblock solid state amps for example you could run another set of dedicated lines that are all independent, ie no conduit, and have their own ground lines etc since these are the devices which might be more apt to have strong coupling with surrounding conduits, wires, environment, etc. By seperating out the high current lines this way would allow them to be routed at a slight distance to reduce the inductive coupling.
I would never let something like this slow me down from getting dedicated lines. I have an audio tweak budget regeneration cycle going right now which pushes a luxury item like dedicated lines out a while so I have time to think about the possibilities. Maybe your're right and this is all worrying for no reason but at least I'll have thrown my idea out here on this forum for critique. It always surprises the great answers I get by discussing on AA here. You all have a great thing going with this website.
Separate dedicated circuits are the way to go. If you can avoid conduit, I think that would be best. Conduit is available in steel, aluminum, and PVC. Steel would have nonlinear magnetic interaction with the power current. Aluminum would avoid the magnetic interaction, but would increase capacitance of line- and neutral-to-ground. It would also have acoustic ringing problems. PVC should be the most neutral of the choices, but would still introduce some sonic vibation behavior. If you have to have conduit, try to wrap the stuff with rubber tape after the inspector has blessed it.
Cheap house wire cable is insulated with PVC. Oyaide makes polyolefin-insulated, carbon-damped cable, but it is very expensive. If nothing is too good for precious, I would look into this stuff.
With me being involved as an ameteur AM radio station operator/ local wireless and wired network administrator (of my home)/ member of a high techish suburban community/ near bustling commercial and military communications and navigations signal hubs my audio equipment in is in the middle of what might very well be considered RF hell. I see the single ground wire, dedicated lines bundle, in conduit, in-wall, service run as a great weapon against RF and significant reducer of the length of the "necessary" ground loops a seperate dedicated lines suffers from and can't seem to let go of this thing. The problem is as I understand it, the only way to pull off this holy grail desired feature of a single ground there has to be a conduit in order to satisfy code. It is safe to assume that if I didn't use the lowest electrical impact PVC conduit material that the conduit approach is no longer an option and my dreams of this single ground wire system go poof in a wisp of smoke.
Obviously PVC isn't a perfect dielectric material so I understand your comment about how it may still be an imperfect solution signal integrity wise. My gut feel is that is less of an issue in my environement than RF immunity is. I don't see a way around that barring finding some more electrically inert conduit material. The other problem with this approach that you mentioned, vibration problems, can be dealt with almost entirely. I can as you point out mechanically damp the conduit if necessary. Maybe some of that expando foam insulation stuff in the wall surrounding a rubber tape wrapped bundle might keep it all holding still.
There are also imperfections in the seperate dedicated line approach. It introduces longer parallel lengths of ground conductor. This means more potential for noise energy to be injected into the signal vs the single wire approach via crosstalk and radio signal reception. To battle the RFI problem the bundle can be more tightly packed. However the tighter packed bundle would have the tradeoff of being more likely to have crosstalk issues. To battle crosstalk issues the bundle may be more loosly packed but that means a tradeoff in RF immunity performance.
What confuses me about your post is it's tough to tell exactly why you prefer a seperate set of dedicated lines over a bundle in PVC that has one low impedance ground wire. The question is: are the noise/signal distortions tradeoffs for the conduit approach worse than the noise/signal distortions tradeoffs for the seperate dedicated lines outside conduit approach you are recommending, and under what conditions is it true? I guess my big problem here Al is my little voice inside is contradicting what you are saying slightly. This worries me a little because your obviously an intelligent and thoughtful fellow. This is a general topic which is difficult to talk about in specifics since everyones situation is different.
I like separate circuit cables because of the hot and neutral isolation they provide. In an environment like yours, a single ground wire would be preferred. It is acceptable per code, as I understand it (disclaimer: I am not a licensed electrician), to tie the separate ground wires together at the audio system. This would almost be as good as a single wire. Almost, because the individual loops between the audio system and the breaker panel can still support resonance modes. The difficulty is finding an electrician who will install exactly what you want, and not try to talk you into a subpanel. A subpanel, even if fed with heavy wire, defeats the isolation afforded by separate dedicated circuits with cables back to the main panel.
A metal conduit must be grounded, and makes a second ground circuit from the breaker panel to the outlet box. A metal outlet box will tie this circuit to the ground wire if you use any audiophile outlet I'm familiar with. Nylon screws and washers to mount the outlets would break the outlet-box connection. I'd prefer a plastic box, but I don't know if such are allowed with metal conduit.
Thanks for replying. That clears things up nicely.
Howdy
I do understand in principle about tweaking every last little bit out.
On PVC I think you'll find those that don't like the sound of it as a dielectric... I wouldn't have a guess what they would feel about using PVC vs. a conductor for power conduits :)
I too have amps which can draw a lot of current: SimAudio Moon W-10 monoblocks each on their own dedicated circuit. Tho they only draw 48 watts at idle they can draw quite a bit since they are happy doing 2200 watts into 2 ohms. I'm sure I never push them anywhere near that hard but their instantaneous current draw can be large.
I have another similar compromise in my system. I have conduits embedded in the concrete floor for the left rear speaker, right rear speaker and to the sweet spot for my transport. (See my room renovation pictures: http://gallery.audioasylum.com/cgi/view.mpl?UserImages=7184&invite=194917041 ) I really wanted to get ceramic pipe for this purpose, but unlike years ago, there isn't much ceramic piping to be had these days. I gave up and put in PVC and chose a speaker wire for the rears which already has air dielectric, etc. (AudioQuest Mont Blanc) and power cords with thicker casing (Shunyata Taipan Alpha Helix.) I don't think I'm hurting too bad :)
-Ted
Hurting? I wouldn't say that! In fact that's one of the coolest looking piles of stuff I've ever seen. I wouldn't even have to be there to assume it sounds amazing.
It's kinda funny, your pictures remind me of my own system. It is more like the redneck, poor man version of the same thing, with mine still very much being a work in progress. We have a similar design approach in the full range speakers and the big amps to drive them, but yours likely cost wwwaaaaayyyy more. Judging by the looks of it yours is one of few of a rare few Asylum systems I've seen that I'd be nervous about putting mine against in a raw SPL competition and yours obviously has an extra level (or two) of refinement in quality mine will never touch. I'm going to try and email you a photo of it this week even though I don't have it posted in inmates systems because I think you'll get akick out of it and maybe even a bit of a laugh. For example where you have a giant wooden shelf in back holding a whole bunch of equipment, in my system in that spot you'll find a full height industrial computer server rack full of my amplifiers computer and various other rack mount gear. Redneck I tell you.
My amps are mid eghties JBL/Urei model 6290's with quieted Pabst fans replacing the stock fans for nearly silent operation. They can draw some current as well when set free (my house wiring really needs an upgrade) as they are rated at 1200W into 8 ohms as I have the fronts configured (bridged). These amps are in fact pro amps I got from Morgan sound in N. Seattle area when they were upgrading to digital. At $50 each I think I scored a fine deal, the owner was a bit tweaked when she found out what the sales guy was giving them to me for. At that price I told hime give me four and I already have more into tweaking them than I paid for them haha. The main problem with them seems to be the fans they come stock with but I solved that. Other than the fans they are dead quiet, sound great to my ears, and pack a big punch. I can't wait to try them on some dedicated lines.
HowdyWell here is old older picture of my old house:
Here's my office before that:
I thought you were in the Seattle area, but I guess I'm mistaken. If you come to the neighborhood you'll have to drop by and visa versa.
-Ted
I'm down here on the South end in Des Moines actually.
It's good to learn I'm not alone up here. Regular folks just don't seem to understand.
Drop me a line sometime when your bored we could shoot the breeze. I've always wanted to hear a higher end system designed for full range and have someone critique what I'm running as well.
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