Apple's new iPhone 7 and iPhone 7 Plus do not feature a 3.5mm headset jack, and yes, that's annoying many people out there. After all, your home speakers, car stereo, headphones, and so on all seem to rely on it.
However, Apple is not leaving you without a way to connect to those systems: the company provides a handy adapter free in the box with every iPhone that connects to the Lightning port on one end and provides an outlet to a 3.5mm jack on the other. If you lose it, you can buy a new one for $9, the cheapest for an Apple adapter.
All of this suggests that there might not be much to that adapter. However, recently released X-Ray images of it, reveal quite the opposite. A lot of the space right below the actual connecting pins is occupied by an integrated circuit, a chip that obviously is tasked with some important feature.
Officially, there's no explanation by Apple as to what it does, but the most obvious guess is that it contains a digital-to-analog converter, or a DAC, in addition to an amplifier and an analog-to-digital converter. That is needed because Apple's Lightning connector is digital, while headphones require an analog signal. It's the DAC that makes that conversion.
Interestingly, additional testing revealed that while that new DAC inside the adapter delivers a slightly worse audio quality than the built-in solution before, the difference might not even be audible to most people. With this, a lot of the mysterious around the curious adapter are finally unraveled.