A few questions:
- Is your PHA-1A identified as such by the iPhone? I.e. when you select the output device in the iOS Control Center is it listed as "PHA-1A"?
- Is the iPhone sending the bitstream data in the native format?
I am asking because with my Sony MDR-1ADAC (which AFAIK is basically a PHA-1A integrated into a set of MDR-1A headphones), when I use Sony's included Lightning cable and connect it as designed to my iPhone 7+, the device is recognized as "Dock" (not "MDR-1ADAC" as it should be). Biggest problem is that everything is output in only 44.1kHz. The MDR-1ADAC supports 44.1kHz/48kHz/16-bit when connected via it's Lightning cable, but with iOS 10.0.x everything is getting sent out at 44.1kHz only. I get this same behavior on iPad Air 2 or iPhone 5S, all with iOS10.0.3.
Interestingly, if I use the iPhone 7+'s included Apple Lighting Earpods, or if I use the included Apple Lightning to 3.5mm dongle, the iPhone sends out either 44.1kHz or 48kHz, whichever is most appropriate for a given source. Yet, I cannot get it to do this with my MDR-1ADAC.
I have the feeling that there a LOT of bugs in the iOS10 lightning audio support right now. Very frustrating...
EDIT: Just to add - I am also getting infrequent, faint clicks also in audio with the MDR-1ADAC connected via Lighting. In fact, it was something I was suspecting I was hearing but wasn't quite sure, as it doesn't happen all that often, but now that I see others with this issue....