What are those weird wires in the audio cables?

Question

Trying to repair a headset cable, I discovered that it doesn't look at all like the “ordinary” cables I used to repair. I was expecting to see, inside the cable jacket, four wires, each one in a wire insulation. Instead, there is:

1. A wire with a white wire insulation.
2. A sort of an orange/gold thread.
3. Something which looks like semi-transparent, very narrow optical fiber, with red, green, or blue thread around it.

I would imagine that the semi-transparent fibers conduct electricity, but I don't get any conductance with a multimeter, including when I try to scratch the surface of those fibers. What are they? And what is the magic which happens inside the audio cables?

Answer 1

Those are normal headphone wires.

• The colored strands are copper insulated in a colored lacquer.
• The core of each wire is a string (for strength as copper wire is not all that strong - especially not when it is as thin as this stuff.)
• The combination of the very fine copper strands and the string makes for a very flexible wire that can stand being pulled on.

You can't strip the insulation off like you would with normal wire.

You would normally use a solder pot to strip and tin the wires all in one go.

A hobbyist won't have a solder pot handy, but you can still solder the wires.

Here's how:

0. Turn your soldering iron up hotter than normal. About 350°C (670°F,) maybe higher.

1. Get a big blob of solder on the tip of your iron:

2. Poke the end of a wire into the solder:

The hot solder will melt the insulating lacquer and remove it.

3. Once the very tip of the wire has solder on it, push the wire through the solder from the side to strip and tin a couple of millimeters of wire:

It helps to have the solder standing by so that you can add solder as you are working with the wire.

4. You will end up with stripped and tinned wires that have a bit of burned lacquer at the transition from lacquer to tin:

Even the copper colored wire is insulated with lacquer - clear, in that case.

5. Strip and tin all of the wires, then solder them to the pins of the new plug:

Once you have the wires tinned, turn the soldering iron temperature back down to normal (270°C or 520°F) to solder the connections.

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As happens, I was working on a blog post on this very subject when your question came up. I haven't published the post yet - I just finished making and preparing 37 photos for it and haven't written any of the text yet.

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If you need a guide to replacing the plug on an Android headset, I've finished the blog post. You can read it here.

Answer 2

I see white, blue, and green insulation on three conductors. Your fourth conductor is the bare copper ("gold"), which is traditionally ground.

The red/white string is probably Kevlar or something similar, and is there to prevent stretching of the conductors when the cable is under tension.

Answer 3

It's been a long time since I (as a 15 to 18 year old...) actually "dissected" one of these cords. What I remember is that the semi-transparent thread-like cores of each wire was apparently fiberglass. I say that because the soldering iron wouldn't melt it. My electronic teacher said it was made this way to prevent the actual conducting wires (wound around the fiberglass cores) from breaking. Fiberglass actually has a very high tensile strength. with the conductive wire and the synthetic rubber (plastic...) insulation around them, the fiberglass would have to break before the wire wound around each wouldn't be able to straighten enough to be stressed unless the fiberglass broke first.