I was away from home spending the holidays with family and while I had fun I also broke my favorite headphones 😞.
A $149 pair of Etymotic hf3 Earphones + headset with a matching set of Comply Foam ear tips. The nicest pocket audio and microphone experience I’ve been able to find.
If you don’t want to follow along for all the story or research I did trying to figure out what to do, just skip to The Repair Attempt.
I didn’t succeed.
I got up too quickly before taking them out of my ear while trying to go calm our dog, the headphones came with it and the 3.5mm jack stayed in my laptop. Luckily the part that disconnected (everything after the black plastic ends in that image) didn’t get stuck in he laptop.
I was about to just buy a new pair, but they’re a bit pricey. They’re note even the “best phone headset” money can buy. Etymotic makes more high end models themselves, they just don’t have inline microphones.
I really like the inline microphone. I started looking into doing a repair. I didn’t find any traces of someone cutting up a pair of Etymotic hf series headphones, so I decided to take notes.
The Setup
Before the TRRS jack I settled for on Amazon arrived I hastily tried epoxying the two pieces back together. It kind of worked and played really scary noises, but I couldn’t insert it into my iPhone all the way.
This is one of the product pictures on the Amazon listing, a breakdown of the parts I purchased.
There’s a TRRS connector, a silver enclosure that screws onto the connector, a plastic tip, and some shrink wrap. We’ll get back to the numbering in a bit.
Quest: Replacement Part Acquired
I knew the replacement I needed to get was a 4-pin TRRS adapter, not a 3-pin TRS one since my headset has a microphone and stereo audio. The last link helped me learn that, I found it while googling to see how hard this would all be after I broke my headphones.
This is probably a good time to mention I have no clue what I’m doing. I didn’t succeed in the repair, I learned a lot while doing though, which is worth it. This is less a DIY repair guide and more of a “oh I think I have most of the tools to do what that might entail” story.
Since I knew the adapter I needed was 4 pin, I felt safe buying it on Amazon because I could look at the photos and count the pins.
Normally I would’ve bought something with a datasheet like this or that. You can click Datasheet and view the PDF to count the number of pins, to make sure it fits the bill. But what I got was on Prime so yeah.
During my frantic googling, I learned about different wiring standards for 3.5mm 4-pin TRRS connections. The article linked earlier referred to it, the conflicting standards are OMTP and CTIA (f.k.a. AHJ).
In the picture from the Amazon listing, repeated here, the 1,2,3,4 sections.
I didn’t read too much into it, and flipped over to Hacker News, but then it was right there too. So I figured okay fine, I started reading into it.
OMTP from what I understand is an older format, the pins on the 3.5mm side (the left half of the image above) go:
| Pin | Purpose |
|---|---|
| 1 | Left Ear |
| 2 | Right Ear |
| 3 | Mic |
| 4 | GND |
CTIA on the other hand was only made to try to post-standardize something Apple started doing, which sound about right. CTIA, all this conflict, me needing to read Hacker News comments, all the injustice stems from the last two rows here[[and some other stuff I don’t know I’m sure, don’t attack me nerds]]:
| Pin | Purpose |
|---|---|
| 1 | Left Ear |
| 2 | Right Ear |
| 3 | GND |
| 4 | Mic |
Just ground in the place of the microphone in the other standard. From what I understand the mic in TRRS works via resistances being pushed down a circuit between the ground and the mic pin, so… I don’t really get the source of the issue, but whatever.
With all that information, and since I seemed to recall all my headset’s buttons working on my iPhone, I decided that my headset’s original connection must’ve been CTIA. Quest complete.
Quest: Find a way to test your work
Basically since the headphones are passive I knew if I passed some sort of power supply into them I must be able to just test the left and right ear manually if they’re speakers.
I was a little worried about what voltage to give it, but while googling I saw people mention completing the circuit using a AA battery. An AA battery is 1.5V charged, so not that gave me a ballpark.
I stumbled upon a weirdly helpful article from another facet of my life. 3.5 mm Headset: Accessory Specification, Android’s specification for all this.
It specifics that CTIA pinout order is required. OMTP support is optional. That verifies my assumption that my headset was originally wired in CTIA.
The page also has this amazingly helpful reference diagram:
Honestly, up until this point I was pretty close to buying a new pair. Or starting to search around for other decent-quality built-in-microphone headsets.
I was also looking at the iPhone Upgrade Program on another tab, while seeing if someone like Blue Microphones had started making headphones compatible with the iPhone 7.
But this felt right. I’m an Android developer during the day time, why else would the Android developer documentation be helping me right now? I don’t even want an iPhone 7.
My iPhone 6s has that unexpected shutdown issue and I haven’t gotten it fixed yet, but my Pixel died too. I don’t want a buy another new phone, there’s no point.
This had to be a sign.
And to be fair, my Astrobarry horoscope for the extended holidays had told me I’d be on a path towards success:
As soon as 2017 begins, you’ll welcome Venus into your zodiac-home (on Mon Jan 2), a lovely influence with which to kick off a new year. Plan to show up to your first week of ’17 with a fresh look, a winning attitude, and/or a seductive readiness to charm others into giving you what you want.
A fresh look, I trimmed my mustache without hating the final outcome on 1/3. A winning attitude, I can do, and hopefully the seductive readiness will help too.
Anyway, the Android documentation’s test diagram alongside people’s mentions of AA batteries made me feel that I had the skill set to decode which connections inside my headphones needed to be connected to which pins on the replacement pair I purchased.
The Repair Attempt
The replacement, well, the two units I got just in case I messed up the first time, arrived. It’s time to get to work.
Let’s jump right in. I knew I had to cut off the old adapter from my headphones, and strip the cable a bit to expose the internal wiring. After a a quick strip with my wire cutters:
Right off the bat, I was struggling. There was a lot of seemingly non-conductive fiber inside the cable. I’ve seen stranded wire before, but this wasn’t anything I’ve seen before.
It wasn’t even any of the variety of stranded wires in this Sparkfun tutorial:
I kept on going, separating the wires that I found inside the freshly exposed section.
You can see the non-conductive fiber stemmed near the non-exposed tubing.
At this point I was ready to start testing. As mentioned earlier, I knew if I supplied the ground of some DC power source around 1.5V into the ground wire, and gave the positive to one of the two speaker cables, I’d be able to hear it.
So I started setting up a test circuit:
I found a 4-pin power wire I was using for a different project and started trying to rig that into the breadboard. But I still didn’t know how to plug in the AA battery.
I started searching my apartment for some alligator clips, and funny enough, I ran into a regulated DC power supply. And, all my alligator clips were next to it.
It has a little knob to set the voltage. I used to use it for a 12V project, it seems the lowest it can handle is around 2.5V.
I probably could’ve tried opening it up and seeing if that regulation is set on the knob itself or the AC inverter, but 2.5 is close enough to 1.5. I used my multimeter to check that it was actually giving off 2.5V and not just the lowest the display could display.
I hooked up the + and – from the power supply into my breadboard, then plugged the ground from the breadboard into the exposed non-labeled copper wire.[[At this point, it hits me: Was the non-conductive material to maintain a set resistance on the wires? Who knows.]]
Before I started putting power through my headphones, I sat down and wrote down all I knew so far for my lab report.
I then wrote out a test matrix, put on the headphones, and started giving +2.5V to different wires. My results:
Quest: Solder the wires and connector
My personal step style is to over educate then jump right in when I feel I’m ready, so I had already watched a few videos and read a few other write-ups on this next part. The soldering.
I liked this video because it’s Revision3, and that’s a name I hadn’t heard in a long time:
The ordering of the internal wires and connector pins they mention is different than what my test circuit said my headphones will need to have, so I’m already feeling prepared enough and ready to go.
The video mentions that the wires inside the cable are covered in a coating to insulate them from shorting and hitting each other.[[I think this feature is what makes it so as you bend the cable, you don’t hear any static like you do on some cheaper headphones?]]
The video mentions that you can just burn it off. I didn’t want to actually light a fire, so I used my heat gun which has come in surprisingly handy ever since I bought it for shrink wrap.
Not a great picture, since I was really trying to speed up and get on with it already:
At this point, I realized I should’ve tried to see if my multimeter detected a live circuit when I probed different points on the same internal wire or one of the internal wires and the ground, before I burnt them.
Well, the multimeter didn’t beep to indicate a current on any of the pairings so let’s hope that’s okay.
At this point, I just wanted to try soldering the thing. I got started.
I tinned the wires one by one, by putting some solder on my smallest soldering iron tip then touching it to each wire.
Soldering iron warm and ready. The connector in one hand of my helping hands, the headphone wire on the other, tweezers in hand to try to position the smaller internal wires in place, I started trying my best.
I tried to start by connecting the hardest to connect wire, which I think I wouldn’t have been able to do if I had connected any of the other ones first.
The pin labeled 1 on the right side of the Amazon product picture, connecting to the blue internal wire corresponding to the left ear.
I just couldn’t do it. The wire wasn’t sticking to the tiny ring. Maybe I needed a finer tip soldering iron. Maybe I needed flux.
I tried to place some solder on the connection itself so I could just bring the small wire close to it and do a love tap, but I ended up wasting the first attempt to a bunch of errant solder.
On the second one, I tried to be more careful and ended up getting the wire to connect to something. But to the ground of the connector, not to the tiny connection I meant to.
I tried removing it from the wall meant for the ground and getting it on the right pin, but the entire connector heated up way too much and the pins started melting together.
The Outcome
At this point I said “I’m hungry” and started cleaning up my workshop because my workshop is my coffee table and my coffee table is my dining table. I took a picture first, which is what you see above.
So yeah, all in all, I wasted ~$20 on Amazon, and some of my time. It was pretty fun, to be honest.
I have a lot of possible quest line paths I could take, from acquiring new tools to attempting different replacement connectors that are easier to solder, but I think at this point I don’t feel guilty just spending the $149 to fast forward to the next part of the main plot line.
The new year is ending soon though, and I don’t think this affected my winning attitude, so let’s hope the seductive readiness part of my horoscope comes through too, who knows what the next main quest will be!
Kasra Rahjerdi 