DIY DC power cables

[Daudio]

6 minutes ago, JohnSwenson said:

The open open shield at one end is NOT the right way to do it. The last time I tried to bring this up...

John,

 

I, for one, would be interested. I don't recall getting a clear grasp of the issue from your previous attempt. And I have been using one-end grounded, shielded, star-quad config, Mogami 2534, DIY interconnect cables for a looong time now. Not that my analog source was that challenging, but it was a best practice from that time. So I'm still very curious about the theory, measurements, and/or listening experiences around this issue.

 

 

P.S. (to All, not just John) why has this thread page expanded its width beyond my normal viewport ??  Makes it hard to read !

 

[Middy]

I cant find it.. can you link it please Jud.

Why I've been nagging Mr S but I didn't realise people threw a fit over a theory...

 

[pl_svn]

1 minute ago, Daudio said:

P.S. (to All, not just John) why has this thread page expanded its width beyond my normal viewport ??  Makes it hard to read !

 

happened yesterday here too 

closed browser's window, reloaded CA main page and all was back to normal

[Middy]

Ok on Android. .

[Jud]

1 hour ago, Middy said:

I cant find it.. can you link it please Jud.

Why I've been nagging Mr S but I didn't realise people threw a fit over a theory...

 

 

It'll be a while, Dave - going out shortly, may not get back in front of a keyboard until tomorrow.

[MikeyFresh]

1 hour ago, Daudio said:

And I have been using one-end grounded, shielded, star-quad config, Mogami 2534, DIY interconnect cables for a looong time now. Not that my analog source was that challenging, but it was a best practice from that time. So I'm still very curious about the theory, measurements, and/or listening experiences around this issue.

 

 

I'm not trying to answer for John S. in any way, but what you are describing above with W2534 and an analog interconnect cable is a different thing.

 

So while I agree it would be interesting to know the theory behind why this is not the best way to do a DC cable, John S. did specifically state in his last post :  "At least for the DC cables an unshielded starquad is better than one with improper shield."

 

I also concur with @Jud that this good news for me as I neither have to try to source shielded cable nor be concerned with connecting it at one end only and then marking the cable's directionality, it's easier not to have to bother with any of that.

 

[R1200CL]

2 hours ago, JohnSwenson said:

The open open shield at one end is NOT the right way to do it. The last time I tried to bring this up I was thrashed by a large number of very angry people (I had no idea shield connection was such an emotional topic for so many people) so I am loath to bring it up again. Part of the problem is that I have no test equipment  right now so I can't PROVE it.

 

At least for the DC cables an unshielded starquad  is better than one with improper shield.

 

I have to make up my mind whether I want to talk about proper shielding at this time or not.

 

John S.

 

Thanks John for your expert feedback. I would very much like if you could talk about proper shielding. I wold love to hear your advice. I was hoping for your comment on my post. 

 

And I agree it's not as simple as I said, cause shielding has to be part of the whole loop, so you need to use shielded cables the whole way, which means that you most likely would have to use a shielded open end USB cable as well, and probably not on the DC power cable. Unless the USB is only signal ?

 

And this can probably can only be verified by measuring, as you are saying but:

 

My reason for bringing this up is that as a designer of low voltage control systems in the Oil & Gas industry, the rule for as long as I've been in the business is a signal loop from the I/O (input/output) control system card, we use shielded cables. They all in the end has the same ground (on an offshore platform), but the screen / shield was always floating in the end. End is where the field instrumentation is. 

 

This is related to 4-20 mA systems with 24 VDC where signal is analog. Digital is on/of (well it is a bit more actually), but still 24 VDC. 

 

I was thinking this way of designing control systems loops, could be transferred to our way of powering things in the audio world. But I could be wrong. I should also mention that the minus of these signal cables is NOT the same as ground.

But some control systems offers a common minus. I think those engineers some times will have callanges ? 

 

So the conclusion is that you have to look at your whole system, and how everything is connected up. This may not be so easy, as we, (or at lest me), hasn't got a clue how my earth and signals (and power) is done between the various devices in my setup. 

 

And I think John has chosen not to use eart, except for his amplifier. 

 

Also to to fully understand all these things, we need some sketches. And they can only cover the design principles. 

 

John your advices is mostly welcome. 

[Daudio]

1 hour ago, MikeyFresh said:

I'm not trying to answer for John S. in any way, but what you are describing above with W2534 and an analog interconnect cable is a different thing.

 

Yes, I know, and am curious partly as to the why of the difference between applications.

 

That, and I made an external LPSU cable for my UTA MMK equipped Mac Mini, from that same W2534*, in a star-quad config and, yes, one-end shield grounding. So I'm curious on that score too !

 

BTW, the Mogami Microphone cable works wonderfully with the Oyaide barrel connector. No problem soldering the paired wires, and the jacket slips freely through the back of the cover. The two paired 24 gauge conductors, result in only about a total 21 gauge capacity, but this is not an arc welder. Is a heavier gauge necessary ? Or more importantly, audible ? I don't know, but would love to find out. In the meantime I'm happy with my cable, except that is, for the recent cloud over the shielding technique

 

Here is a pix of my 12vdc cable for my Mini music server:

 

 

* I still have about 60' of that stuff left !

 

[MikeyFresh]

6 hours ago, Daudio said:

 

Yes, I know, and am curious partly as to the why of the difference between applications.

 

That, and I made an external LPSU cable for my UTA MMK equipped Mac Mini, from that same W2534*, in a star-quad config and, yes, one-end shield grounding. So I'm curious on that score too !

 

BTW, the Mogami Microphone cable works wonderfully with the Oyaide barrel connector. No problem soldering the paired wires, and the jacket slips freely through the back of the cover. The two paired 24 gauge conductors, result in only about a total 21 gauge capacity, but this is not an arc welder. Is a heavier gauge necessary ? Or more importantly, audible ? I don't know, but would love to find out. In the meantime I'm happy with my cable, except that is, for the recent cloud over the shielding technique

 

Here is a pix of my 12vdc cable for my Mini music server:

 

 

* I still have about 60' of that stuff left !

 

 

Very nice looking cable!

 

I too have a bunch of W2534 I could use for this application, and while the aggregate 21 gauge conductors should be ok up to 1.2 amps, I decided to just go unshielded and ordered some of the 4S6 instead, as I managed to worry myself that the X-PE insulation on the microphone cable wasn't necessarily intended for use in higher current applications like a speaker cable would be.

 

Are those worries unfounded? Probably.

[Forehaven]

On 5/3/2017 at 11:44 AM, Michael-Elijah Audio said:

The cable I'm using is - Response WB-1762 (OD 8mm)

https://www.jaycar.com.au/medias/sys_master/images/8954952024094/WB1762-dataSheetMain.pdf

Michael, what dc plug is that?  Seems it'd be ideal for the Canare 4SG which is only 6.4mm.

[Daudio]

45 minutes ago, Forehaven said:

Michael, what dc plug is that?  Seems it'd be ideal for the Canare 4SG which is only 6.4mm.

 

 

If you read back thru Michael's (very welcome !) previous posts in this thread, you will find the links to this French connector.

[R1200CL]

I'm talking to the French Elec. Got an offer. Not to bad. 

Have asked them to ship a couple plugs to the Chinese guy. Offered to pay. No feedback yet. 

 

I personally think the Elec is as good as Qyaide. 

 

 But since I believe people like to have Oyaide, I suppose that what has to be first priority. 

 

What I don't know yet, is if used on ISO regen, such huge plugs as Elec, may become in conflict with the uspcb. 

Maybe perfect for use with an Y-split. (In the LPS-1 connection). 

 

 

[Forehaven]

Humm, his plug doesn't look like the french/Elac plug

http://www.elecaudio.com/en/hi-fi-connectors/285-elecaudio-dc-21g-jack-dc-connector-5521mm-gold-plated.html

 

R1200cl, please let us know when you get a price?  Thx

[R1200CL]

2 hours ago, Forehaven said:

Humm, his plug doesn't look like the french/Elac plug

 

Look at this pic closer. Maybe you change your mind  

 

[Forehaven]

Ok, cool then.  Just wasn't sure

[JohnSwenson]

OK here it is: cable shielding, how to make it work and how almost all cables have it wrong.

 

The first important question is, what is electrical shielding and how does it really work?

 

Lets look at the infamous "Faraday cage". For this discussion it is a metal box, with all sides well electrically connected (no gaps). Shielding means that electrical fields outside cannot be sensed inside. Conversely electrical fields inside cannot be sensed outside.

 

So how does this work? When an electric field from the outside world impinges on the box it causes the electrons in the metal to move, this rearrangement of the electrons creates an electric field inside the metal which exactly counteracts the external field, thus the field is essentially stopped at the periphery of the box.

 

The important aspect here is the part "electrons in the metal move". What are moving electrons called? Current. In order for current to flow there has to be a loop. Current will not flow unless there is a loop. In the case of the Faraday cage, the loop is the whole cage. Lets say an electric field impinges on a side of the box, this causes a current flow that goes all the way around the box back to where the field impinges on the box. If the sides are not electrically connected to each other the current cannot flow, thus the electrons cannot move, and the canceling electric field does not get setup, thus no shielding.

 

It turns out that for AC electric fields it is a little different. Some current can flow due to capacitances between conductors. The electrons can move a little bit one way, then a little bit back. If the frequency is high enough the back and forth movement, which is charging and discharging the capacitance is sufficient for shielding. For a given capacitance the lower the frequency the less effective the shielding. The electrons start moving which charges the capacitance, then stop moving when fully charged, they don't do the full movement necessary to produce the canceling field.

 

So what about shielded cables? I hope is now obvious that for shielding to be effective there needs to be a conductive path from one end of the shield to the other. If there is not such a path the only shielding that is going to happen is for high frequencies due to cpacitances involved with the shield.

 

The best way for the shielding to work properly is a separate wire connected to each end of the shield. This is sufficient for shielding from DC to very high frequencies. Note the shield does NOT have to be connected an earth ground, the "ground" of the circuit at either end, or any thing else for that matter. A cable with a shield the is not connected to anything else except itself (ie a separate wire from one end to the other of the shield) will be highly effective in shielding what is inside.

 

Where does this wire need to go? It can be either inside or outside the shield, but if it is inside it can couple to the signal wires inside, so it is usually best to have it outside the shield. Note it has to be insulated from the shield except for the ends where it connects to the shield. It should intersect as little of the external field as possible so it should NOT be tightly spiraled around the cable. Just running along side the shield is best, although a very loose spiral (say one turn per foot) is almost as good.

 

So some ramifications of this: The traditional "connect the shield to one end and let the other end float" is not good, it does not allow a loop so shielding does not happen very well. If you add the external wire connected to the shield at both ends, then you CAN connect one or both sides of the shield to the signal ground or some other ground, but you don't NEED to for effective shielding. You will find that in many cases leaving the shield completely disconnected from the rest of the circuit is the best way to go, you get the benefit of properly working shielding without any interaction of the shield with your system. You may wind wind up with static charges on the shielding so a resistance from the shield to ground may be useful in some cases in order to dissipate static charges.

 

So how come nobody does this? I don't know. My only guess is that cable shielding has been going on long before the actual mechanism for shielding was worked out, thus by the time it was understood, cable shielding was "standard" and nobody ever even thought about analyzing it based on an understanding of how shielding actually works.

 

But shouldn't the big companies know about this? It seems they don't. I have read several app notes from Belden that state that shielding is only effective at high frequencies, at audio frequencies and power supply frequencies (60Hz etc) it is totally ineffective.

 

Audio people are the only ones that seems to at least empirically know about this. Remember phono cartridges and preamps, there is a little green wire that goes from the "ground jack" on the preamp to the tonearm. Everybody assumes that this is to "ground the cartridge" but what it really does is provide a loop from one end of the interconnect shield to the other, it has nothing to do with whether it is "grounded" or not. So if you have (or had) a turntable you were actually taking advantage of this without realizing it.

 

So there you have it, shielding DOES work, but only if you provide a path from one end of the shield to the other. This is effective even if you don't connect the shield to anything else.

 

John S.

 

 

 

 

 

 

[austinpop]

@The Computer Audiophile

 

Could you please go in and change John Swenson's designation from "Junior Member" to "Audio Pioneer?" Or something similar that is more fitting?

 

Junior Member, indeed. Hah!

[sockpit]

Alex C.

 

I own two of the special DC cables you sell with the JS-2, the star quad 5 footers with oyaide plugs.  Can I assume that since JS designed the JS-2 and sleeps on your couch from time to time that these cables follow the principles generously outlined above?  ?

[Michael-Elijah Audio]

8 hours ago, R1200CL said:

 

 

What I don't know yet, is if used on ISO regen, such huge plugs as Elec, may become in conflict with the uspcb. 

Maybe perfect for use with an Y-split. (In the LPS-1 connection). 

 

 

Don't think that will be a problem - modified Elec and screw type plug

 

[The Computer Audiophile]

2 hours ago, austinpop said:

@The Computer Audiophile

 

Could you please go in and change John Swenson's designation from "Junior Member" to "Audio Pioneer?" Or something similar that is more fitting?

 

Junior Member, indeed. Hah!

 

We'll let John decide what he wants to change it to, under Account Settings > Edit Profile.

[Middy]

 

5 hours ago, JohnSwenson said:

OK here it is: cable shielding, how to make it work and how almost all cables have it wrong.

 

Thank you for reposting this John very much appreciated ?. 

[R1200CL]

4 hours ago, Michael-Elijah Audio said:

Don't think that will be a problem - modified Elec and screw type plug

 

I think you misunderstood. 

 

If you use the new UpTone USPCB between MicroRendu and ISO regen, then you may have a challange. 

 

@Superdad have not put any measurements on his website yet, and in any case I suppose we have to wait until it ships in order to verify.  

 

I may inventing issus here, as I suppose the uspcb is primary meant to be downstream between the ISO regen and a DAC. Not on the upstream/ input side.

 

Although my plan is to have one uspcb both upstream and downstream together with my MicroRendu. 

 

The 90 degree version of the uspcb may solve this potential issue. 

[ElviaCaprice]

15 minutes ago, R1200CL said:

 

I think you misunderstood. 

 

If you use the new UpTone USPCB between MicroRendu and ISO regen, then you may have a challange. 

 

@Superdad have not put any measurements on his website yet, and in any case I suppose we have to wait until it ships in order to verify.  

 

I may inventing issus here, as I suppose the uspcb is primary meant to be downstream between the ISO regen and a DAC. Not on the upstream/ input side.

 

Although my plan is to have one uspcb both upstream and downstream together with my MicroRendu. 

 

I agree, the current USPCB will be a challenge in many cases, sure wish Uptone would make one longer.  For me, it will also be a challenge on the DAC side with the ISO Regen. 

[pl_svn]

8 hours ago, JohnSwenson said:

So how come nobody does this?

 

actually there is a well known manufacturer using this kind of shielding in their most expensive cables

but as far as I understand it... they're also applying some "current" (using a dedicated battery, I believe) to the "shielding wire"

[Daudio]

7 minutes ago, pl_svn said:

actually there is a well known manufacturer using this kind of shielding in their most expensive cables

 

Don't be a tease. name names !