C7 Unpolarized Power Cord

[Laudanum]

You'd be surprised (or maybe not) to find out how many homes arent properly grounded, often due to broken ground clamps or those that have come loose.  Even broken ground wires/strands themselves.  Ive seem homes use the drop cable as ground back to CATV plant because of bad power co. grounds.  On our own plant, the interface between the ground cable and the ground rod with a standard clamp was problematic enough that we began using a special kit that allowed us to weld the ground wire to the rod.  And that in itself helped alot because we had thousands of buried copper rods out there grounding strand, power supplies, power inserters etc. 

[Grainger49]

You are right, I'm not surprised.  Salting my ground rod was a suggestion from one of the most experienced and intelligent EEs I have ever known.  He designed the power distribution for the four green field K-C mills I worked on.  At K-C we often had a "noise free grounding system" for sensitive equipment and a power grounding system.  Both connected to buried triads and bonded together at one point at ground, under ground actually.

Now that I work on a wiring crew for Habitat For Humanity I see ground rods being driven every week.  I wish the crew I work on had wired my house, there are four licensed electricians, maybe more, I don't have an accurate count.  This is a professional crew.

[HF9]

Surprised I didn't notice this thread until now. I'm currently in the process of building my own C7 power cord for an ST35 I'm building here: http://www.diyaudioblog.com/2011/06/customized-dynaco-st35-kit.html . I'm using a C8 connector made by Shurter as the power inlet that I fastened to some FR4 material.

For the cable, I chose to use three 16 gauge silver plated copper in teflon conductors and a grounded shield on the source side, even through only two conductors will be attached at the amp side. There are multiple layers of teflon tape insulating the braided wires and shield. On the amp side, I'm using a low-cost connector from a seller on that auction site: http://cgi.ebay.com/FIG8-C7-style-connector-solder-tags-/170169090572?pt=UK_Computing_CablesConnectors_RL&hash=item279ede420c#ht_1249wt_812

The connector above is made in Japan, and sold from the UK. I'm not sure if there's a U.S. source for it. If there was a slightly nicer $10 plug floating around somewhere, made by Hubbell or Marinco, I'd use that, but I'm not paying $45 for a Furutech C7, no way Jose!

Typically, a stock C7 power cord will have 18 gauge conductors. There is a PS Audio Jewel C7 that is 12 gauge and an Audioquest NRG C7 that's 16 gauge IIRC. These are both around $60-70 street price.

The cheapie C7 connector will accept 16 or 18 gauge wire and provides a nice tight connection.

[HF9]

Finally all done with my 16 gauge C7 power cord:



See all the build notes here: http://www.diyaudioblog.com/2011/07/custom-c7-power-cable.html

[Yoder]

Finally getting back on my feet, and shall throw the big question out. Here is what confuses me when it comes to the C7 unpolarized power cord. Assume that I am using my C7 cord for my MacMini. We plug the cord into the wall that has the grounding pin, and neutral and live blades. Assuming that I have built the cable properly, then how is it that I can flip the C7 end of the cable and plug it into the Mini without causing havoc? Granted, only the neutral and live are going in but it seems that if I flip it that so that I have a live and neutral configuration that this would have an adverse affect. Anyone know what is it that prevents things from frying in this scenario? Thanks.

[jrebman]

Yes, the AC goes into a transformer that has the primary isolated from ground, so there's no earth ground on the mini and the polarity of the hot/neutral won't matter -- technically speaking.  On the other hand, I get two clearly different sound signatures depending on the orientatin -- one way is more mellow and rounded, the other is more dynamic and focused.  There's no right or wrong way, whichever way sounds best to you.

-- Jim

[Yoder]

Hah, now I understand. So, it does have an effect but not like one would expect...snap, crackle, pop.

It is hard to wrap my head around the simple stuff like this when I don't fully understand what is going on.

Thanks Jim.

[jrebman]

Yoder,

Glad to help, and so sorry for dropping the ball on this one -- I should have remembered to answer this for you months ago.

Anyway, hope you let us know when you have that whole system together -- you've got the makings of a really, really nice system there.

-- Jim