The decision to axe the iPhone’s built-in headphone port and simply put an adapter in the box has provoked reactions ranging from amusement to near panic. Why did they do it? Was it worth it? Will other manufacturers copy it? Today we’re going to ignore all of these questions. Instead we’re asking, How did they do it? And since we like taking things apart, we’ll answer with some exploratory surgery and some X-rays.
Apple feels the 3.5 mm audio jack is an antique whose time has passed. But we’re not all prepared to shell out for new headphones just yet, so to ease the transition Apple gave iPhone 7 owners a deal worthy of Oprah—you get a headphone adapter! And you get a headphone adapter! Everyone gets a headphone adapter!
Separately, this little adapter retails for $9.00—making it pretty much the cheapest thing in the Apple store, where you can drop $35 for a simple screen protector. So, you’d probably think a $9 dongle doesn’t have much going on.
Imagine our surprise, then, when our pals over at Creative Electron gave Apple’s new adapter the X-ray treatment:
Thanks to Creative Electron for this X-ray image of Apple’s audio adapter.
There’s actually a lot going on in there. As expected, one end is a simple female 3.5 mm headphone jack, and the other end is a male Lightning connector. But what’s all that silicon around the Lightning connector end? Most of the retail space near the connector is taken up by a single mystery IC.
Image courtesy of the amazing folks at Creative Electron.
We needed a closer look. Thankfully, long-time iFixit contributor and gadgeteer extraordinaire oldturkey03 sliced his adapter open so we could all get a peek inside. He uncovered that mystery IC by the Lightning connector, marked 338S00140 A0SM1624 TW—which doesn’t tell us much, other than it’s an Apple part number.
Thanks to longtime iFixit community member OldTurkey03 for his teardown of the audio adapter.
While the official purpose of this IC is unknown, at minimum we can guess that it contains a digital-to-analog converter (DAC) and amplifier, and its counterpart, an analog-to-digital-converter (ADC).
We know this because audio accessories like earphones (as well as human ears) need analog signals to work—and unlike ye olde analog headphone jack, Apple’s Lightning connector is all digital. The DAC bridges that gap. By the same logic, this chip must also contain an ADC circuit to convert the analog signal from your headphones’ built-in mic into something that can pass back through the Lightning port so your iPhone can make use of it.
In past iPhones like the 6s, both DAC and ADC functions were handled internally. The analog inputs and outputs from the headphone jack (and other components) were wrangled by a single chip on the logic board, a custom Apple/Cirrus Logic IC labeled 338S00105. (In the iPhone 7 and 7 Plus, that same exact chip still exists—because even without a headphone jack, the phone still has to shake hands with the built-in loudspeakers and microphones, all of which use analog signals.)
Apple/Cirrus Logic 338S00105 audio codec in the iPhone 6s (left) and iPhone 7 (right).
The moment Apple’s plans for a headphone adapter first came to light, audiophiles began questioning whether such a tiny dongle—and, presumably, the DAC + amp buried inside—could possibly supply a quality audio experience. Speculation was that, in order to fit aboard the adapter, the audio hardware would have to be so small that corners would inevitably be cut.
Well, here’s a visual comparison of the audio chip on the iPhone 7’s logic board, photographed right next to the exposed chip on the new adapter:
This isn’t an oranges-to-oranges comparison however, because each of these chips handles more than just DAC/ADC. The larger chip is also a codec, and is not believed to contain an amplifier (there are three amps located elsewhere on the iPhone 7 logic board).
In short, a more scientific approach is called for. So upon its release, hi-fi enthusiasts at German computer tech magazine c’t ran a battery of sound quality tests on Apple’s new adapter. After taking baseline measurements from the old-school, built-in headphone jacks on an iPhone 6s and iPad Air, they compared the adapter’s output on iPhone 6s, iPad Air, and iPhone 7:
Hi-fi enthusiasts at German computer tech magazine c’t ran a battery of sound quality tests on Apple’s new adaptor and broke down the results.
The takeaway seems to be that in some areas, the sound quality does measure a bit worse from the adapter than we might be accustomed to. For instance, when playing an uncompressed 16-bit audio file on the iPhone 6s, the dynamic range dropped from 99.1 dB at the headphone jack to 97.3 dB at the adapter. Though keep in mind, this slightly lower measurement is still higher than the theoretical maximum you get from a compact disc (which is 96 dB). So, is it a difference you are likely to notice? If you sit in a quiet room with a really, really good pair of headphones … and you’re a canine, the answer is: maybe.
But it appears Apple’s engineers did their job, and this tiny adapter performs better than most people expected or even thought possible.
Why did they do it? Was it worth it? Will other manufacturers copy it? Give us your thoughts.
They needed a DAC to drive the new enhanced TapticEngine. Easier to steal the one that used to power the headphone jack and make the headphone DAC external than reengineer all those DAC subsystems. As a bonus they would be able to make it waterproof with less engineering. Should be able to be proved if someone can trace the TapticEngine to one of the three DAC’s still on the motherboard.
Notes: The German measurements are only valid for iPhones shipped in Europe, due to EU regulations about maximum volume enforced for devices that ship with headphones – the connector used with a U.S. iPhone will exhibit higher output voltages (and as a consequence a relative higher DNR and lower noise floor)
As for the chip itself, and which manufacturer does it for Apple? My pet theory (which may be entirely wrong) is that it’s a variant of one of the brand new Audio Codecs launched by Dialog Semiconductor. Some of them also seem to match the form factor of this one.
It is no sense having a dac in the external chip if it hasn’t an amplifier after the dac. And there is no place for an amplifier in it. Or is it? I don’t think so, it would be a really incredible miniaturization work!
It is not very hard to integrate an amplifier inside a DAC chip. The hard part is making a DAC with nice linear output.
What I would like to see is if a USB to lightning adapter would let a $9.00 Apple DAC work like many of the USB DACs that people are using for high quality PC audio.
Looking on eBay some of the imported adapters are less than $2.00 so that would make possibly the cheapest USB DAC available and knowing Apple, the audio quality would probably be better than decent, especially if you could power it from a clean supply.
There was speculation that the iPhone simply passed through an analog on the Lightning port. Has this been discounted since it would need to always be a pure digital signal on the wires?
Looking forward to buying a pair of air pods in a couple of weeks!
I REALLLY don’t understand what the “mystery” is about. Regardless what anyone says, all Apple has done is to move the D/A converter from inside the phone to outside. Does it sound better? It MAY sound better, but it has absolutely nothing to do with whether the converter is inside or outside of the phone. What makes it SOUND better is a BETTER D/A converter.
My guess is you’ll find exactly the same chip in the new TB headphones as well.
Really… its not a mystery
There’s digital audio & there’s digital audio.
The adaptor could receive partially-decoded audio from the phone, which would be easily converted to analog. A “Class D” (Pulse-Width Modulated) signal, for example, which only needs trivial amplification with very low linearity requirements. I would expect to see some sort of a capacitor to reduce the high-frequency noise this normally produces, but perhaps a teensy bit of cleverness in the “DAC” chip could do it digitally.
All speculation, mind you, but consistent with such a tiny amount of circuitry.
We need measurements of jitter, because to a very large extent that defines the audio quality. You can buy the cheapest CD player with digital-out, then feed it into an expensive outboard DAC and it will sound brilliant, largely due to the low jitter in the outboard DAC.
Please note: the 1624 part of the number is a date code: 2016, 24th week. That’s when the chip was built
@coolfactor, these adaptors work in older iPhones and older iPhones did not support analog audio on the lightning port.
I got an iPhone 7 Plus a week after launch to replace my 6 Plus. I use Bluetooth headphones most the time, but in my car, which doesn’t have Bluetooth audio, I always plug into the aux port. So when I got the new phone I intended to leave the adapter permanently in the car, but after trying it I found using the adapter caused so much background noise I might as well have been listening to a cassette tape. This was never an issue with my 6 Plus. The idea of consolidating ports is something I can understand and get behind and I like that Apple are brave enough to lead the way for other manufacturers to strip bulk from their products. But the problem here is rather than boldly slashing a path for other manufacturers to follow that will, when everyone’s on the same page again, make the ecosystem better, the fact that the lightning cable is proprietary means they’ve just made headphones as compatible as laptop ac adapters.
That’s actually a good point made. To what degree does interference (background noise) occur now that it’s external and very little if any shielding?
Anyway, I get what Apple is trying to do here, inject some motivation to wireless audio. However I’d have more praises and could get on board if they offered at the same time a better listening experienc. Bluetooth does not sound better and even Apple still doesn’t supported encodings like aptX even with this jack removal. Also the lag Bluetooth adds is horrendous and irritating beyond belief. They didn’t add anything to compel any innovation or adaptation. That would have happened anyway if Bluetooth was a better alternative then the physical line. What they did was basically close the door, added a surcharge (lightning port license fee) and managed to create what is comparible to and essentially adding a micro fee to get music back out of the phone after paying to put it on it. What would have been “brave” woulda been open sourcing the lightning port if it’s so much superior to USB, adopt superior wireless encodings which increase the quality of wireless music opposed to wired interfaces. That would have been “brave”.
Great content. I’ll be picking up an adapter tomorrow and quickly amateur run square wave and RMAA tests on it through a Lynx HILO ADC. 0,37Ω and what appears to be a democratisation of output between devices seems good.
I don’t listen to music averaged above 80dB anyway, so I’m not worried about much besides signal stability, though I also have the sneaking suspicion that Heis.de’s tests are volume-cap limited, if not beset by ADC issues. My measurements of the iPhone 6 (not S) show better dynamic range, but 0,0015% THD rather than 0,001%.
Of course, the tools I have at my disposal are not meant for measuring or calibrating audio outputs.
I’m unsure if you can read this criticism of the adapter, which relies mainly on its jitter performance @ 1kHz.
https://www.facebook.com/larry.ho.heyuan/posts/10157409342390532
I’m mainly agnostic about jitter because I have many acquaintances that swear by DACs that spout loads of jitter, and others that swear against the same DACs. In some instances, measuring bad or good is irrelevant.
Still, very interested to get my adapter tomorrow.
One thing that no one has mentioned is that medical devices (such as for blood-glucose analysis) also use the 3.5mm port. They need full volume (i.e. a good signal) so this may ensure that these would continue to work. I have not tested this yet, but Apple is unlikely to drop an important section of a market (health) it is trying to build.
So what about the included earbuds with lightening connector – does that mean they now have a DAC built into them as well?
I’m not an audiophile, but I am curious to know what else this dongle can be used for–both without and with simple changes made at the pin-out to the digital end.
I am an audiophile and I was immediately disappointed with the sound quality of the adapter on my new iPhone 7 Plus. Comparing side-by-side with my iPhone 6 Plus, the iPhone 7 Plus with dongle sounds noticeably flatter and lacking in dynamics, and I found myself turning up the volume quite a bit more in attempt to recover that lost sense of “snap.” Bass does not hit as hard as I’m used to either, nor does it dig as deep down low. There is also a sense that the high frequencies are somewhat veiled, causing music to lose some of the “air” I was accustomed to on the iPhone 6, making certain types of music sound lacking in transparency. This was via a pair of Sennheiser Momentum 2’s listening to Tidal streaming service (hi-res files). Perhaps with time, more specialty manufacturers will release higher quality adapters – and better DACs – than this one. Of course I could always also go out and buy a dedicated, standalone DAC, but I don’t really want to have to carry two devices with me. So as it stands, as an audiophile, I am massively disappointed. Luckily my ipad pro 12.9″ still has the 3.5mm jack and a better DAC execution (switching between my iphone 7 Plus and the ipad pro is a night and day difference), so I’ll probably carry my ipad with me more when I want better sound quality.
@Ptan1101:
I’m sure you hear what you hear, but the data doesn’t bear out those opinions. Both my measurements, and others show that the adapter is good to great. I’d love if someone could conduct a large-population volume-matched double blind ABX test. It may be that listeners can tell the difference, but I doubt that one would be chosen en masse over another, listeners being ‘audiophiles’ or not.
Headfi’s science forum has an amazing post #292 showing that the major difference is just THD/jitter, but at such a low level that likely it is inaudible.
http://www.head-fi.org/t/627111/what-is-the-sound-quality-of-iphone-ipad-ipod-touch/285#post_12872457
My own measurements:
re: THD and jitter: http://ohm-image.net/opinion/audiophile/thd-jitter-apple-lightning-to-35-mm-headphone-adapter-vs-iphone-6
RMAA: http://ohm-image.net/data/audio/apple-lightning-35-mm-headphone-jack-adapter-24-bit
@ohm don’t try to reason with an audiophile with science, he will just tell you that he can still tell the difference.
Unless it’s double blind of course. Then he won’t be able to tell an iTunes Plus track on an iPod Shuffle, from a FLAC played through a $1000 receiver and a tube amp. Lol.
But if we want the best sound: isn’t it an advantage to have the digital audio stream available from the lightning port? All you need is a set of headphones that have good DA and amplifier built in. Then you can tune the DAC and Amp specifically to the characteristics of the headphones. (Which is one of the best ways to get really great sound. ) And feed it with digital sound from the iphone.