Disclaimer: I purchased the adapter in this article direct from Apple. It is a steal.

Relevant links:
THD and jitter: Apple's Lightning to 3,5 mm Headphone Adapter VS iPhone 6
RMAA: Apple iPhone 6 24-bit
RMAA: Cozoy REI 24-bit
RMAA: Astell&Kern AK70 24-bit
RMAA: Arcam MusicBOOST 24-bit

Purchased separately to the iPhone 7, this adapter costs 9$ USD. It hisses less than an Astell&Kern AK70 and outputs a stabler signal under load than both the AK70 and an iPhone 6. It sustains quality signals under load better than many DAPs and most iPhones I’ve tested in many years, all while spitting output voltage similar near the level of an iPhone 6.

Vis-a-vis the iPhone 6, it averages higher THD and jitter, which may negatively affect the adapter’s perceived audio quality, but so far, no one has collated the data from large population double blind ABX listening tests (a fantasy of mine) to confirm that assumption. It is possible that the heat and mild bloat I hear in midrange chimes and some low-voiced percussion elements is due to jitter.

For now, the only thing that matters to me is that this adapter measures better than it should for a stop-gap solution. In some metrics, it even shows noticeable improvement on the iPhone 6 design.

It’s 9$.

Very good.

Below are its RMAA measurements.

Source: iPhone 6
ADC: Lynx Studio HILO LT-TB
Computer: 2012 27" iMac
Cables: 1,5m Hosa Pro 3,5mm stereo to dual 3-pin XLR (around 8$)

Loads:

NL - no load
SM2 - Earsonics SM2
ES7 - Audio Technica ES7
DT880 - Beyerdynamic DT880/600

24-bit TARGETS and loads +0dB (volume matched to iPhone 6’s maximum).

End words

If you expected this 9$ adapter to be perfect, you’re an imbecile. It’s an interim fix designed to mollify the whinging masses. It performs above and beyond its asking price. Physically it fills the 3,5mm-shaped hole in the latest iPhone. And while it shows a few unavoidable audio errors, it impresses.