Iron Tips: Soldering Headphones and Enamel Wire

We’ve all had that treasured pair of headphones fail us. One moment we’re jamming out to our favorite song, then, betrayal. The right ear goes out. No wait. It’s back. No, damn, it’s gone. It works for a while and then no jiggling of the wire will bring it back. So we think to ourselves, we’ve soldered before. This is nothing. We’ll just splice the wire together.

So we open it up only to be faced with the worst imaginable configuration: little strands of copper enamel wire intertwined with nylon for some reason. How does a mortal solder this? First you try to untwine the nylon from the strands. It kind of works, but now the strands are all mangled and weird. Huh. Okay. well, you kind of twist them together and give a go at soldering. No dice. Next comes sandpaper, torches, and all sorts of work-a-rounds. None of them seem to work. The best you manage is sound in one ear. It’s time to give up.

Soldering this stuff is actually pretty easy. It just takes a bit of knowledge about how assembly line workers do it. Let’s take a look.

Every soldering station on an assembly line will have three things. A roll of brand new solder, flux (I like Kester 951, you can buy it in a pen), and a nice soldering iron. That’s all you need.

dsc01106
Since I was at a hackerspace I had an ancient roll of solder, a terrible soldering iron, and a mysterious tube of flux I didn’t recognize. It still worked.

So what is enamel wire anyway? Enamel wire starts off as, typically, a freshly drawn copper strand so there’s absolutely no oxidization or surface film on it. It’s then immediately run through an enamel mixture (typically polyurethane) and dried. This results in a very thin, practically invisible flexible coating all along the strand. The coating isn’t exactly perfect, when looked at under a microscope there will be obvious thick sections along its profile depending on how it was wound, the speed it was coated, and how the coating was dried. Either way, the name of the game is to selectively remove this coating on all the little strands at once without removing any where you don’t want to.

Flux is cheap, frustrated hours of debugging is what costs ya!
Flux is cheap, frustrated hours of debugging is what costs ya!

Since this coating is so thin it doesn’t take much to break through and get to the shiny copper underneath. Going back to the assembly line, all it takes is a bit of heat and flux and you’re good to go. The nylon stranding can be safely ignored, it melts and floats to the surface of the solder bead during soldering. As long as you have flux it will keep the remaining organics from interfering. This is why you may see some black specs on the surface of a typical connection to enamel wire.

As for soldering the wire. The first step is to make sure you have a really clean cut into the strands. For this I recommend first carefully prying away a generous amount of shielding. Then, with a brand new blade on a utility knife, slicing the stranded ends flat against a cutting mat. Even with my nicest end cutters, the strands were just too thin to cut nicely.

connectionmade
Lap Splice. Gerrit Coetzee, 2016. Medium: cardboard, flux, enamel wire, solder, deadlines.

Next, simply apply a generous amount of flux to the end of the enamel wire you’d like to solder. It doesn’t hurt to flux the tab or wire you’re trying to connect it to as well. Try to thread or intertwine the wire to its mating part without disturbing any strands. Then, use good solder and bond the usual way. The trick is to apply heat until you see solder just creeping up the enamel wire. It will be pretty hard to see as only the enamel closest to the joint will burn away cleanly enough for wicking to occur, so a magnifying glass is recommended.

For larger gauges of wire this technique will work too, up to a point. It’s only when you get to the serious gauges of enamel wire that a bit of sandpaper is productive. For the small stuff flux and heat is your friend.

72 thoughts on “Iron Tips: Soldering Headphones and Enamel Wire

    1. I prefer a lighter on the medium light gauges. It burns off the enamel leaving the copper, I’ve never found anything as efficient. Light gauge will melt the copper too, so that’s fine grade sand paper, heavy won’t burn the enamel very well, that tends to be a job for a stanely blade. The neatest job can be done with electrolysis but it takes a while and is best done on mass. Note: A lighter won’t work so well for the braided style copper wire you get in some more expensive headphones.

      1. You want to remove the enamel, not the copper. How do you want to remove an insulation by electrolysis? The lighter leaves the copper badly oxidized and I don’t see how you would treat the hair-fine wires of a typical high-flexibility headphone cable with sandpaper. That would be similar to trying to shave your beard with sandpaper :-)

        There is one method with fire I used once with some success: Take a small container like a metal bottle screw cap and put a tiny amount (like 5mm high) of denatured ethanol into it. Light it, burn the enamel in the ethanol flame and then dip the glowing copper into the liquid alcohol and extinguish the flame. The alcohol cools the copper and prevents it from oxidation, it probably reduces traces of oxide which have formed already – similar to flux.

        But normally it is much more easy to use a hot (380°C to 400°C) soldering iron and plenty of flux. The hot flux creeps between enamel and copper and partially dissolves the coating like a solvent

        1. Fine stuff, roll them on the sand paper, don’t rub them (:
          Heavy gauge, you’d be surprised, I discovered that by accident, I thought that too. It appears to work quite well on the plastic created enamel. Pealing it and blasting it off relatively quickly when you apply plenty of current. Try a nice 40A ATX (:
          Fire, for certain gauges at least, seems the best solution for me. As long as you remember to blow it out quick, the flame can travel up the wire like a firework fuse.

          1. You’re over complicating it and risking damage to the copper, creating a weak spot in an already fragile wire. Use an iron, some flux (I use rosin core solder instead of flux for this generally), and spend a moment trying to slowly tin the wire from the tip to whatever length you want to strip the enamel back. You remove the enamel, tin the tip, and have a nice clean undamaged wire underneath.

          2. I’m with CR on this, use a lighter, then scrape. with the abuse the headphones take around my house (i have to repair my daughters at least once a month) the soldier joint will outlast any cord I put on them, best thing for me is to sacrifice a $2 set of ear buds to salvage a $20 set of headphones, and it keeps my skills sharp.

        2. I’ve always just burned the nylon away with a Zippo lighter and then applied a generous amount of solder to burn away the enamel and wipe with a damp sponge. Have a lot of the stuff in my repairs and hacks around the house that have stood up for around 6 years. I’ve used it in everything from headphones to an Xbox360. The rubbing alcohol might be the key though, I always dip my wire in rubbing alcohol before and after tinning to eliminate the easier to overlook source of cold solder joints (contamination).

    2. What if it’s aluminium wire? I guess it should be possible to solder aluminium under a protective coating (high temperature grease or oil) using some special flux. Or may be a protective gas atmosphere. Anyone with experience in that field?

      An other way would be micro spot welding or ‘bonding’ like what microchip makers do.

      Next time I come across an aluminium wire headphone cord I’ll have a closer look into it. May be I can find out how the makers made the connections.

    3. You can also use a trick with regular aspirin pill. Put the end of the wire on the pill, and heat it up with soldering iron with some solder on the tip. But beware, doing that the pill will produce fumes which are quite unpleasant, probably toxic. So doing this, try to hold your breath, or do this outside.

  1. I wish it were possible to get wire with a few strands of gold or something similarly ductile wrapped around a kevlar or spectra thread and maybe silicone insulation like a multimeter probe. Modular individually replaceable 3.5mm tip and earbuds and we would not be jacking around with shortening and tinning crappy enameled Cu at stress points.

    1. Find an old Bell or AT&T phone handset. They use something called tinsel wire. This is fine stranded copper wire spiraled around a latex (?) core. When stretched or bent, the core diameter shrinks as the spiral opens up. Phone cords NEVER went bad.

      1. I have a pair of AKG headpones that are 20+ years old, and the cable & jack are still original. These are my “work” phones that have travelled a lot, had office chairs roll on it etc. It IS possible to make a headphone cable that will last.

  2. I’ve always dipped the tip of the wire in flux (I’m still using the same tub I got from Ratshack at least a decade ago), get a big blob of fresh solder on my iron and then poke the wire into the blob and hold till I see smoke come off (beyond the initial smoke of burning flux of course). Easy and it only takes a few seconds to burn off the enamel and nylon. Fixed many a pair of broken headphone wires this way.

    1. At my factory, jumper wires even have a use-by date. The teflon insulation is laser etched to give better adhesion to the adhesive securing the jumper to the board. Over time, these etches “heal” somewhat so that the adhesion is no longer good enough.

      1. Just be aware that taking stuff out of a dumpster is considered stealing stuff from your employer. Which might get you in trouble and/or fired if someone doesn’t like you. This is why i a) always ask if i might take it home and b) always ask for a signed permit to take the thing outside of company premises, despite the fact that i am officially allowed to take pretty much anything with me.

          1. I believe that would fall under the “causing an underage person to commit a crime” category or somesuch and thus still get you in trouble.

            @BrightBlueJim, you’d still be guilty of theft, you just don’t get fired on the spot for theft, only afterwards when you show up to your job after your prison sentence with a criminal record.

            Just go up to the front desk and ask nicely. If you get a No, too bad, walk away.

        1. Bzzzt! In the states, at least, California vs. Greenwood (https://en.wikipedia.org/wiki/California_v._Greenwood) settled that one. If it’s trash, “the Court believed it to be “common knowledge” that garbage at the side of the street is “readily accessible to animals, children, scavengers, snoops, and other members of the public” ” which of those you are, when liberating expired solder etc from the dumpster is a matter of opinion.

  3. I’ve had headphones where the “wires” were essentially tinsel, like on a Christmas tree; they just shriveled to nothing with the heat of the iron. I suspect crimping is the correct way to handle these.

    1. Rosin flux core doesn’t go rancid, as far as i know. At worst, maybe it draws in moisture or contaminants. I’m still using up some old (lead! -gasp-) solder. I promise not to stick it in my mouth.

  4. My late 60’s can of flux still has some left and it works.
    Use the knife and heat to remove the molded soft plastic off the stub of the jack. A portable bench vise makes this easy to do from start to finish. Once down to two (3 for TRRS) patches of soldered metal imbedded in the hard plastic of the plug, touch the tinned ends of the wires in just a touch with the right sized blob of solder and GOOD. Longer time for the ground at the base of the plug.
    Here is the best part, with little exposed wire tie a knot in the wire around the post with fresh silicone or Goop under and pull it tight. Add a layer around and smooth with a wet finger. You can make a pea sized soft yet strong end without that long protruding body and the “elephant trunk” strain relief which transfers the strain into your phone’s jack. The glue won’t stick to most jacket stuff but the knot keeps peel down to where it’s not a problem.
    This is worth doing with a brand new plug if it fits the description above. Your pocket and phone will love it when you sit down etc.

    1. Heyyyyy, I want some late 60s flux, had some red shit that was great, but could only replace it with some green shit, which is better than nothing, but it ain’t the red shit.

        1. The pre-Alpha is sporadically dumping output to the great bit bucket in the sky. i.e. disappears not a trace rather than hung in mod hell, or at least doesn’t appear within a day+ very often, so switched again when it didn’t show first time, but this time, surprise, turned up when I reposted.

  5. I’ve learned this trick that seemed to work well. I have always used aspirin with these enameled wires. Just heat the wires on top of an aspirin tablet. The melted aspirin cleans up the enamel and solder will stick to the bare tiny coppers. Just be careful with the smoke from the aspirin. It smells quite bad or even give you head ache

    1. woah aspirin? sounds like liver damage (normal useage anyways)
      a flame/lighter will weaken the copper if it gets hot enough,
      but you wouldnt notice, it’ll break soon again either-way!

      personally, i just use the high-wattage setting on an iron and moan about the fumes later.

      i personally would not try soldering telephone handset cord in front of anyone, or even at all if i can avoid it, because ive tried it… (unless wires inside are “normal” or at least headphone enamel)

  6. Don’t be afraid to turn the heat up, I always have success with either my 65W iron or a soldering station turned up to 400C. Also, forget about aspirine – just use a good flux, not the rosin or anything embedded in the cheapest flux from China.

  7. For this, my biggest regret was not to ask, a bit of that phenolic gel that we used to decap enamel wire. Nasty stuff but worked very well. We sticked the desired length in the gel, took it out, waited a bit and wiped it of with a rag, ready to solder.
    But what was in that gel? It did smell like phenol, was acidic…

  8. For much better reliability, separate out those plastic strands (which are not nylon because they do not stretch), and use them to make a strain relief. After soldering the wires, take a few wraps of the plug with the fibers making sure the wires have a bit of slack, and then apply a *small* drop of superglue. If the superglue doesn’t go off, sprinkle on a dab of baking soda. Keeping the strain off those tiny wires makes all the difference.

  9. What I was taught to do is turn up the iron to 700 degrees, and get a nice ball of solder on the tip. The just lay the end of the wire into the solder and wait for the enamel to bubble away. Starting the solder at the base of where you want your tinned end and working towards the tip of the wire.

  10. Had to do this recently to replace a wire on an electret mic with a white wire to hide against shirts. Used a cheap £0.25 pair of earbuds for the white wire, conveniently with plug ready attached.
    The tiny wire strands inside were really hard to separate into bundles by colour. Spent a while checking carefully with a magnifier and then testing once I’d soldered them I’d not crossed any.
    Flux and solder did a great job.

  11. I hate messing with enamel wire. Any time I have to replace a cord on a headphone I buy a cheapo 4 foot or so headphone plug to 2 RCA jack cable and cut the RCAs off and solder them to the headphones. They last a lot longer than messing with the original cables.

  12. I’ve never had much trouble soldering this kind of wire. But TINSEL wire – that stuff’s a REAL pain to work with. Springy strands of copper *ribbon* that break easily and are often very hard to solder even with really good flux, wound around a core that, depending on the specific wire, may or may not melt out of the way when you solder it. I’d take on the repair of half-a-dozen of the cables described in the article above before I’d take on one cable made with tinsel wire. It’s great for durability and resistance to breakage by bending, but it’s nasty stuff to work with when you do finally have to repair it.

  13. What I do is unwind the nylon from the wires, give it s short blast with a burner, and I mean less than a second short, and it’ll shrink away, then the enamel wires that I twisted back together get a short exposure of the flame of a (small) burner just moving over them in passing, very short though since they can’t take much heat without turning into carbon.. Then I if need be put the end on a piece of cardboard and brush it with some sandpaper, and then put a dab of solder on the tip of an iron and tin the ends.
    Only issue I have is the wires always being very minimum, so very weak, and you need a good way to reinforce the whole assembly once you soldered it to something. One way I used was to bend a bit from a paperclip over the mantle of the wire and press it with a small pliers so you have something to secure a strain relief to.the mantle so the small center stands are not getting force on them. I tried shrink tubing to do the same but that didn’t last.as strain relief on itself.

    The direct soldering technique shown in this article only works with some wires, and not the majority of those I encountered. I guess it’s the kind of enamel used? Or a combination of the kind and the thickness of the copper.

  14. You can also use a trick with regular aspirin pill. Put the end of the wire on the pill, and heat it up with soldering iron with some solder on the tip. But beware, doing that the pill will produce fumes which are quite unpleasant, probably toxic. So doing this, try to hold your breath, or do this outside.

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