Jeff Suovanen, writing at iFixIt, tears down Apple’s new headphone dongle:
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.
Those x-ray photographs are pretty incredible.