I’ve spent the past four months in Shenzhen, China, modifying an iPhone 7 to add a fully functional headphone jack. To the best of my knowledge, this is the first time anyone has done anything like this.

In April, I decided to finally upgrade my iPhone 6s to an iPhone7 to get better camera quality for the videos I was shooting when I was out on adventures in the industrial markets and manufacturing world. But I was super annoyed that it doesn’t have a headphone jack! I already have headphones I really liked, and I didn’t like the idea of having to keep track of an adapter just to use them.

So I figured I’d add my own – after all, how hard could it be?

It turns out, really really hard. But possible.

I went through a ton of iterations and debugging to get this to work. The hardest parts were the electrical design and getting everything to fit inside the phone. Specifically, because I was using the logic from an Apple headphone adapter and a headphone jack from an iPhone 5, I had to find space to put them without breaking anything else. I feel like I got extremely lucky about finding space inside the phone. There was inexplicably a lot of extra room in the lower left hand corner, right where I wanted to put the headphone jack. And because I was connecting the headphone adapter to the lightning jack, I needed to figure out how to make the lightning jack still work for things like charging and syncing to a computer.

I ended up designing lots of circuit boards that were more complex than anything I’ve ever done. I had three iterations of PCB designs manufactured, and 4 different flexible PCB designs.

I also ended up having to buy lots, and lots, and lots of spare parts. I went through 3 complete iPhone 7s, a handful of screens, and countless internal components (mostly bottom cable assemblies and taptic engines).

And I had to buy some new tools. I got a fancy binocular microscope for tiny soldering work (including hand soldering my own BGAs), and had to seriously level up my soldering equipment.

The nitty gritty

I’m pretty proud of the final implementation. I took apart an Apple lightning to headphone adapter, put that inside the phone, and hooked it up by man in the middling the lightning jack with a flexible PCB. The PCB has a switching chip that switches between connecting the headphone adapter to the phone by default, and then disconnecting it and connecting the lightning jack when something is plugged into it. I have a couple other timer chips that briefly disconnect everything from the phone when something is connected/disconnected to improve the reliability of the phone detecting when something is plugged/unplugged (otherwise it sometimes gets confused).

The final flexible PCB uses 5 mil/5mil traces and 0.5mm pitch BGAs. Which is pretty darn tiny. I managed to hand solder these under the microscope, and it turned out to be much easier than I expected, despite being my first time really doing any surface mount design or soldering. If surface mount scares you, buy a microscope! It’s a total game changer.

You can get the kicad files and gerbers here: github.com/strangeparts/niubi-headphones

This design is open source under an MIT license, and you’re very welcome to modify and improve on this design, and even manufacture it yourself. If you do, I’d love to hear about it.

This isn’t just about a headphone jack though – I think this design can be adapted to put other lightning based adapters inside an iPhone, while still allowing the lightning jack to function. It’s mostly just a matter of finding room inside the phone!

FAQ

Q: Who are you?

A: I’m Scotty Allen. I’m an American engineer, entrepreneur, and hacker. I’ve worked at Google and several other prominent Silicon Valley startups. I’ve been traveling the world full time for the past 3 years. I’m a nomad, which means I don’t have an apartment or house anywhere that I rent full time.

I’ve spent about half of the past two years in Shenzhen, China, learning about the electronics manufacturing scene – the industrial markets, factories, and back alleys where the world’s electronics are made. I started Strange Parts as a way to start telling stories about my adventures.

Earlier this year, I made my own iPhone 6s from parts I bought in the market.

Q: Where did you get the parts?

A: I bought most of them from the cell phone repair markets in Huaqiangbei in Shenzhen, China. These are public wholesale markets that target cell phone repair businesses all over the world. I also purchased some official Apple headphone adapters from the Apple stores in Shenzhen and Hong Kong.

Q: Couldn’t you just buy a $10 headphone adapter instead?

A: Yes. But that’s less fun.

Q: How much did it cost?

A: I haven’t kept perfect track, but I’ve spent easily thousands of dollars on this project. I’ve bought 3 iPhone 7s to take apart, a handful of new screens, several handfuls of backs I mutilated, and countless other parts I broke. I paid a factory to do 7 manufacturing runs of circuit boards. And oh god the headphone adapters. I bought lots and lots of official Apple headphone adapters to take apart.

Q: Why didn’t you use a chinese copy headphone adapter?

Believe me, I tried. I couldn’t find any that fully worked. Either the buttons on an apple headset wouldn’t work, or they didn’t detect when I unplugged the headphones. Or they just didn’t work at all. But I wish I’d been able to, as it would likely have been much cheaper.

Q: Does this work on iPhone 8?

I don’t know – I haven’t seen one yet! But I’d like to take a closer look at that once they’re available.

Q: Can you charge the phone and listen to music at the same time?

A: Sadly, no, because of the way the circuit is designed. Either the headphone jack is connected to the phone, or the lightning jack is, but never both at the same time. To fix this would require a pretty serious engineering effort, that would require a much deeper understanding of the lightning protocol than I currently have.

Q: Where can I get my own iPhone with a headphone jack?

A: Sadly, this design isn’t quite ready for mass manufacture just yet. It was really hard for me to put together a single working phone without breaking any internal parts. I hope that others build upon my design to make it easier to manufacture, or that Apple brings back the headphone jack into their phones.

However, for the diehard Strange Parts fans, I made some special circuit boards just for them. You can find out more in the _Strange Parts Store_.

Q: I want to manufacture your design. Is that ok?

A: Yes, please do! The design is open source. I hope that you can improve on what I’ve done, and make it available to more people. And if you decide to do this, send me an _email_. I’d love to hear from you!