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My headphones sometimes don't put out sound in one of the channels, so I opened them up and this question came to mind:

Shouldn't the 3 copper cables that connect to the mini-jack be insulated? One seems to be pure copper, I'm not sure how they changed the color of the other 2 to red and blue but it still looks like bare copper to my eyes.

picture of opened headphones

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  • \$\begingroup\$ I fixed the problem with my speakers just by simply untangling the wires a bit and putting it back together, I haven't a problem since, maybe somewhere the coating wore off and there was a short? \$\endgroup\$ – satur9nine Oct 25 '12 at 0:00
  • \$\begingroup\$ Just wondered the same thing when I took apart my headset and discovered what appeared to be bare/uninsulated wires touching each other. I figured there was some sort of clear coating for insulation, especially since they were nearly impossible to solder to another bare copper wire. \$\endgroup\$ – etherice Feb 24 '15 at 1:53
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They are insulated. Each individual strand is coated in blue, red (is it red?) or clear enamel.

It makes soldering it a bit of a pain, but makes for very flexible wires, and also reduces the high frequency impedance of the wire by massively increasing the surface area of each wire.

It is called "Litz Wire", and the reasoning behind it is to reduce the Skin Effect which causes increased resistances in AC waveforms.

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    \$\begingroup\$ The cables on a broken pair of ear buds I'm looking at have a radius about half of the skin depth of .25mm wikipedia sites at 60 KHz in copper, yet are of this form. A cable would have to be at least three times larger than that for the loss of any cross sectional area below the skin depth to start to be significant. \$\endgroup\$ – Chris Stratton Dec 11 '11 at 20:01
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    \$\begingroup\$ Quite probably - but it does say each strand should be less than the skin depth in diameter. Yes, 60KHz is higher than the human hearing range, and most audio systems will be filtering out anything above there. But just think how thick the cables would be if they were sized for 20KHz... \$\endgroup\$ – Majenko Dec 11 '11 at 20:03
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    \$\begingroup\$ skin depth would correspond to radius, not diameter as you only loose the part further than that inside. Even at a radius of two skin depths, only 1/4 of the total cross section is lost. And it would be deeper at 20 KHz by a factor of the square root of three. \$\endgroup\$ – Chris Stratton Dec 11 '11 at 20:07
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    \$\begingroup\$ That's all very well, but it doesn't get away from the simple facts that a) it is Litz Wire, and b) the reasoning behind Litz Wire is to reduce high frequency resistance. Maybe that is overkill in this specific instance, and it's being used for its flexibility (as I mention in the 2nd paragraph of my answer), but it is still Litz Wire. \$\endgroup\$ – Majenko Dec 11 '11 at 20:10
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    \$\begingroup\$ I didn't say it wasn't litz wire, I pointed out why the skin effect was likely all but irrelevant in this application. \$\endgroup\$ – Chris Stratton Dec 11 '11 at 20:22
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The wire looks like enameled wire to me, basically copper wire coated with a very thin insulating material.

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It probably isn't Litz wire.

The secret of Litz is the way the insulated strands are woven. Like rope, the strands are twisted into bundles, then the individual bundles are themselves twisted. This means that each strand spends an equal time at all layers in the cable. It is done to reduce proximity effect with adjacent bundles at Radio Frequencies.

This is of course expensive and requires special machinery. At audio frequencies there is no advantage, so headphone wires are just multiple parallel strands.

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