Earlier today, Apple’s Lightning to 3.5mm adapter received the teardown treatment, which revealed that it includes a small digital-to-analog converter (DAC). Now, a German website, which has run extensive tests on the audio adapter to determine whether or not there is any sound degradation, has confirmed that the iPhone 7 with 3.5mm Lightning adapter does sound worse than iPhone 6s with 3.5mm headphone jack (via BGR).
Below is a computer-generated translation quoted from the source:
The results are clear: with an iPhone 6S, the dynamic range worsens by 4.5 dB(A) for 24-bit music files. For the iPad Air, it worsens by 3.8 dB(A). The signal also gets worse for 16-bit music files, even if they aren’t that drastic: the dynamic range worsens by 1.8 dB(A) and 3.1 dB(A) for the iPhone and iPad, respectively.
However, it must be emphasized that these results aren’t too bad since the difference is going to be completely imperceptible to most people. In fact, even some audiophiles with an incredible ear for sound won’t notice the difference unless they’re listening to high-quality 24-bit audio files.
So if you mostly listen to Spotify or Apple Music on your iPhone, chances are you won’t even notice the difference.
Of course, this is just one set of tests, so don’t take them as a foregone conclusion. One unscientific test by AppleInsider claimed the new Lightning EarPods sound better than the 3.5mm headphone jack, so it’s hard to say if anything is conclusive at this point.