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iFixit's iPhone 7 audio adapter teardown reveals mystery circuity

There's a strange chip lurking beneath the surface of Apple's 3.5mm headphone adapter for the iPhone 7.


Creative Electron provided iFixit with an X-ray scan of Apple's 3.5mm-to-Lightning headphone adapter.

Creative Electron

There's a strange chip lurking beneath the surface of Apple's 3.5mm headphone adapter for the iPhone 7 and 7 Plus.

iFixit, which routinely conducts teardowns of popular gadgets, partnered with Creative Electron to examine an X-ray image of the dongle included with every new iPhone.

The scan, accompanied by a closer look at the guts provided by a contributor to the site, showed that most of the retail space on the Lightning connector end is occupied by a single integrated circuit. The only clue we have to determine its purpose is an Apple part number labeled "338S00140 A0SM1624 TW."

Without knowing for sure, the iFixit experts guess the chip is actually a digital-to-analog converter (DAC), an amplifier and an analog-to-digital converter (ADC).

What the heck are those things? Because Apple traded the 3.5mm jack for a Lightning connector, the iPhone 7 is now fully digital, which means a DAC is necessary to convert the digital signal back to analog, so your ears can pick up the audio. Likewise, the ADC circuit turns analog signals (like the one from the microphone built into your headphones) into something the Lightning port can interpret.

The iPhone 7 and 7 Plus have their own DAC and ADC circuits inside as well, but the big question is whether or not using the adapter will affect overall sound quality.

A German computer tech magazine did its own scientific testing and compared the headphone jacks on an iPhone 6S and iPad Air to the adapter's output on an iPhone 6S, iPad Air and an iPhone 7.

It concluded that although there is a very slight drop in dynamic range when playing an uncompressed 16-bit audio file, you won't likely notice a difference using the adapter unless your ears are perfectly tuned and you're listening through supremely top-notch headphones.

Check out iFixit's complete teardown report and let us know if you've noticed a difference using the adapter down in the comments below.