Soldering The Thinnest Wires Ever Conceived: Headphone Modding

Acrylic insulated wires stink, for sure, but when they're stranded and micro-fine, they stink WAY more.
Acrylic insulated wires stink, for sure, but when they’re stranded and micro-fine, they stink WAY more.

I may use this blog to post mainly iPhone or software related articles, but I am an electrical engineering student, and as an EE, I love me some good, clean hardware. Therefore, when my favorite pair of earbuds kicked the bucket the other day, my first thought went to the in-box iPhone headset and, more importantly, how much those earbuds suck. My favorite bang-for-the-buck earbuds EVER are Skullcandy Full Metal Jackets, primarily because I got them at TJ Maxx for $25. In general though, they have silicone pads that seal out sound, instead of the hyper uncomfortable iPod earbuds that fall out and sound like crap. I was super bummed when my FMJs broke, but luckily, the part that broke was on the plug end of the earphones. That is, both earbuds themselves still work fine, only the plug is dead. My thought was to cut the crappy iPhone buds off their cable (which includes a microphone and remote button) and graft on my beloved FMJs.

The only thing stopping me? These heinous, hellish stranded acrylic-insulated wires:

The traditional method for dealing with single stranded acrylic insulation is sand paper – you just sand the plastic sheathing off the conductor. The problem HERE is that, clearly, these are NOT single stranded. Trying to sand them with even the finest sandpaper results in a frayed mess that looks like a frayed cotton thread. Without getting the insulation off, though, you can’t solder the wires together or otherwise make any connection. Another method is to try to melt the acrylic off with the soldering iron itself, but this can get messy plastic on the iron and, more importantly, the prolonged heat exposure has a tendancy to melt the jacket farther up the wire.

everythingBeforeWork
Notice my friend, the pencil torch, on the right. IDEA!
torchBurning
The torch makes quick work of the insulation. Check out the secondary flame though: that’s the insulation burning off BEYOND the spot directly in the torch flame.
wrapping
Prepping the joing for solder.

My favorite method: The melting technique got me thinking, though, and being a pyro, it wasn’t long before I saw the pencil torch sitting on my bench and had a brainstorm. As it turns out, burning the acrylic off outright works quite well, and with the extreme heat of the torch, the wire heats up so quickly that it doesn’t have enough time to conduct much of that heat to the jacket above. The result is a fairly clean removal of the insulation, at least plenty to make a nice solder joint. The real trick is to move FAST! Only burn the very end, because that will usually be enough to catch the acrylic on fire for a few more milimeters up the wire, and as SOON as you see the wire start to glow, remove the heat, because that’s how you know there’s no more insulation over that portion (it’s already burned off) and if you let it sit there, the wire will melt almost instantly leaving you with none to work with.

The prepared wire. It's difficult to see, but if you look closely, you can make out the slightly different metalic look near the end. That's lightly-soot-covered but uninsulated wire. Solder, with a little coaxing, will stick to this.
The prepared wire. It’s difficult to see, but if you look closely, you can make out the slightly different metalic look near the end. That’s lightly-soot-covered but uninsulated wire. Solder, with a little coaxing, will stick to this.

Now the trick is to actually solder the wires. You’ve got them stripped and ready, but they’re still super fragile. I used two sets of tweezers to wind the two ends around each other. Really all this requires is a whole lot of patience.

shrinktube
Shrink tube shrunk. The piece of blue on the left is to go over everything, and then there’s another red one behind it to go over again.

After the joint is fixed enough to not fall apart during soldering, you can go ahead and start soldering. The wires are so small that the solder doesn’t really stick, so what you have to do is, as quickly as possible, melt the solder onto the iron, but with the joint DIRECTLY in the middle of the two. If you do it right, you get a big melted bead ON the iron, but with the wires running through the middle of it. Drag this up and down the wires, and that will be enough to solder them together. Try not to leave extra – it’s brittle and these wires can’t really flex. Also, DON’T FORGET TO PUT YOUR HEAT SHRINK TUBING ON FIRST. I CAN’T STRESS THIS ENOUGH, I ALWAYS FORGET. I used multiple pieces, two very small ones on the individual conductors, then at least two over the whole system for strength.

Another helpful tip is to use the torch to shrink the tubing too. You don’t want the tube in the flame, that will catch it on fire. You also don’t want to leave the torch pointed at it long, that will to. The trick is to wave the flame so that the plume of hot air above it licks the tubing. When this happens, you’ll see the tube shrink fast. Keep going back and forth until you don’t get any more shrinking. It takes some getting used to, so maybe practice before you torch your headphone cable.

The finished product is a thing of beauty. Ok, maybe not, but that’s mostly because I ran out of white heat shrink tubing. Oh well.

theguts
The guts. The cannibalized Skullcandy cord and the crappy iPhone earbuds in their proper place: cut apart.
The glory. This is the completed product, gory red shrinktube and all. On the plus side, my FMJs now work again, and with a microphone and remote play/pause/answer/hangup button to boot!
The glory. This is the completed product, gory red shrinktube and all. On the plus side, my FMJs now work again, and with a microphone and remote play/pause/answer/hangup button to boot!

But wait! If you acually tried to do this yourself at home, you probably noticed something peculiar about the iPhone headphones. Namely, what the DEUCE is that red/green twist?

What is that red/green twist and what is it doing in my right earbud?!
What is that red/green twist and what is it doing in my right earbud?!

As it turns out, it’s the microphone cable. That makes sense – there are two copper-colored ground wires, one for each bud, there’s a red wire for the right bud, and there’s a green wire for the left one. That leaves at least one wire for the microphone, so one of the red/green twist is probably also a ground, and one is for the mic. My guess is that the button in the headset shorts the mic return line to ground, and the iPhone hardware looks for that, but it’s mostly inconsequential. Maybe I’ll play with it at some point, but for now we’ve got everything we need.

The real question at this point is, what is that twist doing going all the way up to the right earphone? Short answer? Nothing. The twist just dead ends in the headphone, the only connected wires are the red and ground. So you can just ignore them. I’m not sure why Apple chose to continue them past the mic, but whatever. Cut them off so they don’t short against your solder connections, and that’s all you need to worry about. It turns out thy’re used as an FM antenna for iDevices with integrated radios. Don’t worry about them unless you have an iPod Nano (and you actually use the radio).

So now you can solder ultra fine wires, and maybe you even got a nice new headset out of the process. Finally, I’d like to thank everythingicafe.com forum user Zerologic for this (coral) forum post, which is where I got the info on which wire was which. Sadly, I can’t properly link to his site since the forum requires you to log in to see profile information.

145 Comments

  1. […] Many people find themselves frustrated when working with headphones. The tiny coated wire can be a real pain to work with. They are so very very small, and usually coated.  We generally just end up doing a quick “sand and tape” which just isn’t very high quality.  [Alex] sent in some tips that can really help you get those repairs or modifications going. […]

  2. May 24, 2009

    Did you try with an aspirin? Just put the wire on the aspirin and with the iron press there. The acrylic substance from the wire will disappear. WARNING: Aspirin emanates a bad smell smoke. DO NOT STAY WITH YOUR FACE ON TOP OF THE WIRES AND ASPIRIN.

    Your idea is also great. I like it.

  3. May 24, 2009

    I have NEVER heard of using an asprin. Which obviously means that I have something to try tonight :). If it works as well as you say, that’s NUTS. How long do you have to let it sit, though? The problem I always find trying to melt the insulation off with the iron is that it takes too long and the jacket way above where I’m working melts.

  4. May 24, 2009

    Hello! Any chance you can give me the exact pin-out or wiring schematic for the iphone mic/headphones? I’ve built a “line in” adapter using a 4 conductor mini plug, but I think I must have something wrong, and don’t feel like destroying a pair. Thanks! -J.R.

  5. […] Many people find themselves frustrated when working with headphones. The tiny coated wire can be a real pain to work with. They are so very very small, and usually coated.  We generally just end up doing a quick “sand and tape” which just isn’t very high quality.  [Alex] sent in some tips that can really help you get those repairs or modifications going. […]

  6. Pedro
    May 24, 2009

    I had a problem with those wires a few days ago when adapting a macbook’s isight to a usb cable. next time i’ll try both solutions.

    thanks

  7. Seraptin
    May 24, 2009

    Isn’t the long extra wire the antenna for the radio. Im not really sure if the IPhone has a radio-function but most sony handys do and they need the headphones plugged in to serve as antenna.

    Just my 2 cents 🙂

  8. May 24, 2009

    Sennheiser Noiseguard headphones have six of those micro-wires in one insulated jacket. The best way to remove the enamel coating on the wire is to lay them flat and heat a razor. Gently apply the edge to the wire and pull. You will see the enamel coating come off the wire. I you heat the wire for more than a few seconds you may overheat the wire and will become brittle.

  9. May 24, 2009

    Jake: I do know that they have a phenominal warranty. Perhaps the best part of that warranty is that they only want you to send in the plug for a full replacement. Luckily, that’s not the part I needed for this mod. I basically get two sets of headphones out of it 🙂

    Seraptin: The iPhone doesn’t have an FM radio, and if it’s a cell antenna, it’s piggybacking on a different contact on the plug. There are only four, and they’re all used.

  10. May 24, 2009

    World Of Sound: That’s absurd. Unfortunately, this joint is a bit brittle too, due to the solder. Hence the multiple shrinkwrap layers.

  11. Conairh
    May 24, 2009

    I’ve been soldering headphones that way for years. I didn’t realise that this wasn’t a standard and widespread practise.
    But I use a cigarette lighter instead of the pen torch. I don’t find that the sheath melts at all. I also use a bit of tinning grease to get things going (I figured the intense heating would cause lots of oxidation and it would be good to get rid of it).
    Nice post.

  12. Nocturnal
    May 24, 2009

    These things are usually designed to be soldered at high temperature (about 400 degrees celsius). Its much easier to solder them to something rather than to themselves.

  13. LarrySDonald
    May 24, 2009

    My standard method is to fry them with a standard butane lighter, holding it just a little above the flame. The acrylic usually burns off pretty smoothly. Then on with some shrink tube, wrap (once upon a time pigtail, now inline), heat, layer of solder, shrink as usual, done. I’m no audiophile though, so I could easily have messed up way bad without noticing.

  14. May 24, 2009

    Thanks for the tips. I have a pair of Bose headphones that are extremely comfortable and have fantastic sound, but after only a few months of use one of the cables has some sort of break. I think it’s at the joint where the left and right split apart. I’ve been terrified to cut the wires and try to put a new plug on the end. If I don’t cave in and send them back to the factory for repair, I’ll try your methods.

  15. May 24, 2009

    For a pair of headphones as nice as those, I’m not sure I’d do the same thing. Unfortunately, this solder joint is still FAR more brittle than the normal wire without the joint, and I expect that it’ll probably start to be a problem within a year of solid use. To be specific, I doubt this headset will last two semesters at college next year. Really, the only reason I even bothered is that I had nothing to lose: to get the skullcandy buds replaced under warranty, they want you to cut off and send in only the jack, and the iPhone headset was crap to begin with.

  16. Darren Morris
    May 24, 2009

    Alex – Thank you. You could have sent them back under warranty, or bought better or longer lasting headphones, you could have spent another $25 and just replaced them, maybe even learned to accept the apple headphone sound. But by not doing that you’ve shown us there are others willing to invest $100 to repair a $25 item. Ingenuity, perseverance and maybe a little crazy make anything you “improve” or “fix” so much more fulfilling than any off the shelf product. Keep it up!

  17. […] a quick “sand and tape” which just isn’t very high quality.  [Alex] sent in some tips that can really help you get those repairs or modifications going. Written by startme in: Hack A Day […]

  18. ivan
    May 25, 2009

    Turpentine on cloth also works -then you can rub off the coating. This works well with wires so fine that if you tried burning the coating off, the wire would burn as well. Then twist and soldercoat, leaving the end no more brittle than the rest of the wire.

    I’ll have to try that aspirin trick tonight -might be just crazy enough to work fine. Under the kitchen fan I guess, considering those vapours…

  19. al
    May 25, 2009

    You can actually just make your mechanical connection and then solder through the coating. It solders this way without any problems. The coating melts off and does not interfere with the solder wetting out properly.

  20. meaux
    May 25, 2009

    I believe you are speaking of “LITZ” wire.

    So many years ago, I can remember my father working with this wire. He would dip the wire into a dilute solution of hydrochloric acid, which disolved the coating, and then into a lacquer thinner to neutralize and clean.

    It was near impossible to bring the multiple strands back into shape and thus he would take a single strand of very fine uncoated wire and spiral that along the length of the prepared Litz, and solder.

  21. Dave
    May 25, 2009

    I’m a radio engineer, and often fixing HP’s for careless ops. But yes, those tiny strands are a pain.
    Also, that 3rd wire isn’t always expendable. Usually it’s the ground cable and is definately required.

    The sure fire method:

    Liquid Flux
    (available at most hobby/hardware stores.. Canadian Tire for one ex, and not very expensive)

    Use just a little bit on the tip of the stranded wire and it’ll absorb into the cabling.
    Get some solder on your iron
    Briefly touch the iron to the tip of the wire, and the solder will quickly and smoothly flow over the tip of the wire.
    Once you tin both ends like this, you can then attach them.

    The key is to be quick and not use too much liquid flux, so you don’t burn too much of the wire away. You’ll find that tinning wire ends with liquid flux, especially stranded cable, works excellent since it practically pulls the solder into place.
    Yes, there’s solder with a flux core, but trust me when I say this works better.

    WARNING
    Liquid flux is an acid. Don’t get any on you. If you do a lot of work with it, keep some solder remover handy. (the remover is a skin irritant, but better than acid)

    To apply, I suggest either long stemmed Q-tips, or even easier, get a small glass bottle with a plastic cap and applicator brush. (Metal lids will quickly be corroded)

  22. May 25, 2009

    I think you might be trying to suggest that the ‘third wire’ (which is actually two, twisted) is shielding, which is grounded and prevents RF interference. In this case, that’s not true. It’s definitely the microphone wire, and it definitely dead ends in the earbud.

  23. As/400
    May 26, 2009

    Use a bic lighter instead for removal of the insulator. Less of a headache.

    As/400 Out

  24. Jesse
    May 27, 2009

    This was a great post! Thanks a bunch, got some great use out of it. I also just sent in my skullcandy headbuds for a warranty replacement, this just gave me a second pair.

  25. uldics
    May 30, 2009

    I was about to suggest aspirin, but then i got it in search allready. Anyway, I had same problem of soldering tiny-many stranded wires (POTS) and was told it was impossible. Then (some 20 years ago) my grandfather told me , I should try aspirin. It worked! I got those fumes inhaled, quite unpleasant, but I’m still alive (soviet product; I mean not the aspirin, but me, hehe). Now, I find it rather hard to find clean aspirin anywhere, allways some combination with taste enhancers or vitamin C. Another solution (to another problem), if you need to solder to iron (Fe) you can use HYDROCHLORIC ACID which is weakened by Zinc (until it no more releases Hydrogen gas (nice explosions, but write a testament first). But you have to make a clean solder and clean it thoroughfully, else you will get corrosion.

  26. Mozzyb
    June 15, 2009

    You can also just use a lighter to remove the acrylic. I did it today. Worked fine. And then you dont need to worry about the copper overheating.

  27. June 19, 2009

    Hey this is great. I suck with a soldering iron though. Do you know anywhere that does this? Or if I sent you the headphones I wanted this done on (plus a reasonable fee) would you do it on mine?

  28. July 4, 2009

    You Probably could have gotten another pair of full metal jakets from skull candy if you just called or emailed them.Skull candy does full warranty, no questions asked free replacement. anyways what your doing is pretty cool.

  29. July 4, 2009

    I mean, if you’d done a Ctrl-F for “warranty” you might have noticed, but I suppose I’ll say it again.

    The beautiful part of this whole thing is that skullcandy only wants the plug back for the sake of saving on shipping (or something). Since that’s the part that broke, and the part I replaced, I saved the old set and successfully got a new one under warranty.

    And it’s serendipitous too, since I’m a much bigger fan of the old 9mm FMJs than the new 11mm ones that they shipped me. The 9s have so much more low end that they leave the 11s sounding tinny and weak.

  30. cmltow
    July 7, 2009

    “Don’t forget the heat shrink” I was laughing my @$$ off when I read this part! I can’t think of a time that I didn’t forget to put the heat shrink on. Always in a rush….to do double the work.

  31. July 7, 2009

    I had to resolder these probably 3 times a side just because I kept forgetting.

  32. Tim
    July 10, 2009

    Hi, I was after a how to on splicing headphone wire and came across your tutorial, I havent got the kit or patience for the way you did it but noted the burning you did at the start, so just for the hell of it i pretty roughly twisted the two sets of wires together and then got a lighter and burned the twisted area, blew it out pretty quick and voila it worked, no fiddley soldering, have done it twice just to see if it was a fluke and it worked fine second time too.

  33. steven
    July 27, 2009

    i just followed these directions to connect my iphone headphones with my etymotic hf4’s (with a broken plug on the connecting end, which caused audio to only come out of the left side). everything is working great – thank you!

    a cigarette lighter worked nicely to burn the coating off, since i didn’t have the ability to use the heating method described here. on the first try, i was able to get everything working but the mic/track changer button that comes with the etymotics. after experimenting some more, i figured out that i had to get at the middle white wire *only* (NOT the green and red wires surrounding it) to connect with the etymotic wire that connects to the mic/button.

    next time, i’m going to try connecting it to the new iphone remote (w/ volume control, mic, track change) instead of the etymotic remote that doesn’t have volume control.

  34. Alfonze
    August 9, 2009

    Off Topic (apologies).
    The third finest wires I’ve seen were running down the arm to the read-write heads in a hard drive. They used to be fair-dinkum insulated wires, but usually now look more like copper tracks on a substrate.
    The second finest inside a LED connecting the external legs to the actual diode.
    Possibly the finest I’ve seen were inside an IC, through the glass window of an EPROM, again connecting the external pins to the chip itself.
    I wouldn’t imagine any of those are fixable by mere mortals (not sane mortals anyway).

    But anyway, some handy tips and information here. Thanks very much.

  35. DeadlyDad
    August 16, 2009

    A few tips:

    1) Whenever you are heating fine wires, use pliers/tweezers/etc. as a heatsink, so you won’t melt the insulation you aren’t removing.

    2) For flexibility, wrap a slightly larger strand of wire around a second piece to form a ‘spring’ slightly longer than the tinned ends of the broken wires, tin both ends of the spring, leaving the center clear and the middle section untinned, slip the broken wire ends into the ends of the spring, solder them in place, and finally shrink tubing over the whole thing. The unsoldered ‘spring’ section will allow bending, as well as relieving strain if the cord is pulled on.

  36. Kulawend
    August 16, 2009

    This is what I do when there’s a short in my headphone wire…

    1. Take apart the headphones.
    2. Strip and solder a new headphone wire to the headphones (it helps to have the wire plugged into your iPod so you can see if it’s working)
    3. Put back together the headphones and enjoy.

    I’ve used this method with all kinds of headphones and it never fails, just make sure you don’t overheat the headphones with the soldering iron. You might want to practice soldering if you’ve never done it before.

  37. September 4, 2009

    Why dont you just Buy TWO Receivers Like the TWFK-30017.000 From Knowles Acoustics and a Pair of CI series and Make your Own Headphones? You can purchase all of the items and Make your Own Custom Earphones that will sound ever bit as good as the UE3 or the Shure E530 PTH!
    You can read about it on Head fi org
    UNDER DIY Section.

  38. Rogan
    November 5, 2009

    Thanks! I couldn’t figure out how to get the coating off, but a quick hit on the torch took care of that easy and fast. You helped me save a $65 pair of headphones.

  39. Craig Larson
    November 9, 2009

    Why is it that the manufactures use such worthless small wires? Designed obsolescence? Over the years I’ve trashed about a dozen phones because of some irritating short. I’m not that hard on them either. The wires just crap out. I just soldered-repaired a pair only to have a short develop in another area. When I was soldering the small coated strands I inadvertently pulled one and it slipped right out. So I tugged on the remaining bundle and an inch of wire came off as easy as a Gerbil’s tail. The entire line is probably segmented with shorts waiting to happen.

  40. Iheffner
    November 20, 2009

    I’m currently trying to do a similar splice of a set of skullcandy smokin’ buds onto an iPhone 3Gs earbud cable. The insulated wired are a nightmare. As for the remote signalling the iPhone, I found that the circuit for the mic maintains about 5 ohms resistance until you press the center button. It the drops to effectively 0. The (+) and (-) buttons cause spikes in resistance on the left and right earbud circuits. Clearly the iPhone monitors for and responds to these signals for music/volume control.

  41. oskar
    January 14, 2010

    Thank you so very much for this. Saved the life of my favorite headphones.

  42. […] and a couple of nifty tricks I discovered. First off I have to thank Alex Whittemore’s blog post which helped me figure out how to prep those tiny evil wires for soldering. First thing first. Chop […]

  43. jim
    January 31, 2010

    hey, i need help, i’ve got a 13 strand wire, 24 gauge each with a teflon jacket surronding them. problem is that the jackt is difficult to remove (actually has to be pushed back and the wires are fragile). wiring is for ccd application therefor need ul approval for use in human body. internal wiring is extremely fragile and need to develop a technique for soldering to a micro pcb. help!!!!!!!!!!!!!!!

  44. January 31, 2010

    First, I am by no means a professional electrical or manufacturing engineer (just a student in the former) and I can certainly not speak to problems that might arise using a device inside the human body. So consult someone with more credentials before you try to do anything.

    But what I would say is this. If it’s going in a body and it’s electrical, I’d say encase it in some kind of biologically nonvolatile plastic resin (something that won’t leach BPA into surrounding tissue, for example.

    As for actually manufacturing the thing, do you mean “how would you do this by hand for a prototype” or “how would you manufacture these in production”? I know that the point of teflon insulation is it’s extremely high melting point. It’s almost impossible to melt with a normal iron, and I suspect that if you get teflon goo on your conductor it’ll be almost impossible to get rid of and get a good connection. In the worst case that you can’t mechanically strip the teflon insulation, I’d say that for a manufacturing process, your best bet would be to use a precision UV laser to burn the insulation off then heat the pad/conductor for soldering.

  45. April 4, 2010

    Holy cow!!! I have tried to make connections with these wires of the the devil before but never could, tonite I used the lighter to burn off the coating and it worked slicker then… well pretty dadgum slick!

    Thank you!

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