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Author Topic: Combining power/signal in one wire idea  (Read 8563 times)

Mike Sullivan

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Re: Combining power/signal in one wire idea
« Reply #30 on: November 10, 2015, 07:24:04 am »

Mr. Sullivan may be thinking that the current offerings of Siamese cables are too thick and bulky, so replacing one of the wires in a 12/4 configuration with an audio signal cable would make for a smaller, easier-to-handle package.

Hit the nail on the head.  We have a couple laying around that we have tested, which feel more like 8/4 or bigger cables, since all they are is two wires in a common jacket.  That's what I want to avoid, it just look awkward and bulky.  Better than running two cables, but still, it stands out.  I just would like to at least see if a small power cable company would be able to help experiment with the idea, to see if there's a really feasible way to do it.  Hence, why I haven't jumped on buying a pre-made unit yet.  This is just to try the idea...
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Jonathan Johnson

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Re: Combining power/signal in one wire idea
« Reply #31 on: November 10, 2015, 11:42:08 am »

P.P.S. -- It is very important to coil and lay out Siamese cables properly. Improper coiling and layout could negate common-mode rejection if the cable is allowed to become twisted so that the audio signal cable is wrapped around the the power cable.

After sleeping on it, I realize that the issue of common-mode rejection negation may not be correct. However, proper coiling and layout is still a really good idea, if for no other reason than to preserve the ability to coil and lay out the cables properly by preventing kinks and twists.
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Tim McCulloch

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Re: Combining power/signal in one wire idea
« Reply #32 on: November 10, 2015, 01:53:52 pm »

Hit the nail on the head.  We have a couple laying around that we have tested, which feel more like 8/4 or bigger cables, since all they are is two wires in a common jacket.  That's what I want to avoid, it just look awkward and bulky.  Better than running two cables, but still, it stands out.  I just would like to at least see if a small power cable company would be able to help experiment with the idea, to see if there's a really feasible way to do it.  Hence, why I haven't jumped on buying a pre-made unit yet.  This is just to try the idea...

The reason the cable is physically so big is the NEC 640.8 requirement that all conductors must have insulation rated at highest voltage present.  The easy way for a cable manufacturer to accomplish this is to extrude another rated jacket over the signal wires, then filler to keep it round, and then extrude an overall jacket.

Several months ago there was a listing in the Marketplace for a Meyer-supplied siamese cable, the O.D. was close to 0.75 inches.  Looking at the Meyer spec sheet, the cross section illustration showed a lot of insulation and filler.

For the time being I expect this will remain the case, Mike S.
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Rob Spence

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Re: Combining power/signal in one wire idea
« Reply #33 on: November 10, 2015, 01:56:46 pm »

Hit the nail on the head.  We have a couple laying around that we have tested, which feel more like 8/4 or bigger cables, since all they are is two wires in a common jacket.  That's what I want to avoid, it just look awkward and bulky.  Better than running two cables, but still, it stands out.  I just would like to at least see if a small power cable company would be able to help experiment with the idea, to see if there's a really feasible way to do it.  Hence, why I haven't jumped on buying a pre-made unit yet.  This is just to try the idea...

They are not just 2 wires in a common jacket. They are a 300 volt rated cable such as SJ and a low voltage twisted, shielded pair cable in a common jacket.

You do realize that there is a significant cost to modify tooling to produce a new cable type? Also, there is significant cost in testing to meet regulations to get approvals such as UL which may be required since you are combining 600 volt (in the case of SO or SOOW) with a low voltage cable which would also need to be insulated for 600 volts in order to be in the same jacket.

I suspect the resulting cable would be much larger and heavier than you would think.
Oh, and costly as not much would be produced as I don't see a big market for it.

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Stephen Kirby

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Re: Combining power/signal in one wire idea
« Reply #34 on: November 10, 2015, 05:11:36 pm »

I make my own by putting SJ and audio cable though braided sheathing.  It doesn't have the pinch resistance of the extruded cable with the secondary overmold, but it is much thinner and lighter.  The SJ power cable already has it's own pinch resistance (I suppose you could use SO but all the factory made siamese cables I've seen are SJ) so it's basically equivalent to running the speaker manufacturer's supplied SJ power cables and regular audio cable of your choice.  Just neatly bundled together for convenience and a bit of extra cut resistance. 

One thing with integrated conductors is that you still need a breakout at either end as with a snake.

You could use shrink sleeving.  A few years ago I used to make some power cables for the Bradley by armoring existing cables with extra layers of shrink sleeving.  Blowing compressed air down the sleeving holds it open while feeding the cable through.  It might take awhile to shrink it all down though.  We would run it through an inline SMT reflow oven (25' long conveyor belt) with people at either end feeding and catching.

Not only is the sheathing easier to work with, it is also more flexible than shrink sleeving pulled down tight against a bundle.
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Mike Sullivan

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Re: Combining power/signal in one wire idea
« Reply #35 on: November 10, 2015, 11:52:26 pm »

Thanks everyone for the advice.  I understand if this was a full on production line product it would have to be submitted, I honestly just wanted to try it out and see if it worked.  Seeing as how the power wires would be rated way over what they would be used for (think about it, less than 5-10A at 115v) so there wouldn't be an issue with higher voltages, although I know that people are leery of shorts and spikes.  I just thought it would be a fun project if I found a feasible way to have it done.

I make my own by putting SJ and audio cable though braided sheathing.  It doesn't have the pinch resistance of the extruded cable with the secondary overmold, but it is much thinner and lighter.  The SJ power cable already has it's own pinch resistance (I suppose you could use SO but all the factory made siamese cables I've seen are SJ) so it's basically equivalent to running the speaker manufacturer's supplied SJ power cables and regular audio cable of your choice.  Just neatly bundled together for convenience and a bit of extra cut resistance. 

One thing with integrated conductors is that you still need a breakout at either end as with a snake.

You could use shrink sleeving.  A few years ago I used to make some power cables for the Bradley by armoring existing cables with extra layers of shrink sleeving.  Blowing compressed air down the sleeving holds it open while feeding the cable through.  It might take awhile to shrink it all down though.  We would run it through an inline SMT reflow oven (25' long conveyor belt) with people at either end feeding and catching.

Not only is the sheathing easier to work with, it is also more flexible than shrink sleeving pulled down tight against a bundle.

That sheathing looks really tempting. Any recommendations on places to get it from?  First look on a Google search shows Techflex, are they any good or does it really matter?
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Stephen Kirby

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Re: Combining power/signal in one wire idea
« Reply #36 on: November 11, 2015, 04:55:03 pm »

I got my sheathing from a local electronics surplus place.  Never really looked into any quality differences between suppliers.  For years it was all made to the same military spec.  There are probably cut rate versions out there now but I don't know which they are.  There is a version that's not supposed to fray.  I just put shrink sleeving over the end.  Also, folks have posted in other threads on the subject that if you cut it with a hot knife, it won't fray.
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John durisko

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Re: Combining power/signal in one wire idea
« Reply #37 on: November 11, 2015, 06:40:21 pm »

For the record
Top left is standard 13/8 speaker for size reference.
Top right is what Meyer sells as a veam break out cable. Notice the individually jacketed pairs. This is what would have a male veam multi-pin on one end and perhaps a L6-20, Xlr and Phoenix connector at the speaker.
Bottom left is Meyer veam cable. Notice the power conductors not individually jacketed but audio and RMS are.
Bottom right is CBI MTPD Siamese style cable.

Why anyone would want to "reinvent the wheel" is beyond me. If you purchase pre made cables and something happens because of them, it's a lot easier to point the finger than if you come up with a home made solution.



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Mike Sullivan

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Re: Combining power/signal in one wire idea
« Reply #38 on: November 12, 2015, 09:26:32 am »

Why anyone would want to "reinvent the wheel" is beyond me. If you purchase pre made cables and something happens because of them, it's a lot easier to point the finger than if you come up with a home made solution.

I understand where you're coming from, but I would at least like to try it myself.  Who knows, if I can find a suitable way to have it done, then it may become a business venture.  I know companies have done it already, I just want to see if it can be made more compact.  That's all.  Thank you all for your love and support  ::)
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Tim McCulloch

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Re: Combining power/signal in one wire idea
« Reply #39 on: November 12, 2015, 02:27:58 pm »

I understand where you're coming from, but I would at least like to try it myself.  Who knows, if I can find a suitable way to have it done, then it may become a business venture.  I know companies have done it already, I just want to see if it can be made more compact.  That's all.  Thank you all for your love and support  ::)

Here's your hint:  it's mainly about 2 things:  dielectric strength of the individual conductor insulation on the AC mains side and the over all jacket that is still required over them; and the physical robustness properties of insulation, filler and outside jacket of the entire assembly.

That means to make it smaller will require more advanced (expensive) insulating materials.  Look to the aircraft industry - very little rubber or vinyl, mostly Teflon and similar materials.
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Re: Combining power/signal in one wire idea
« Reply #39 on: November 12, 2015, 02:27:58 pm »


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