HowardCWith x1s u could probably get a USB female to lightning converter and use that USB input. But I am not sure if iPhone allows you to hook up an external dac.
MorisamaIf Iphone alowes dongles it should not have problem whit X1S, they should be treated the same. My old X1S connects fine whit android so the X1S does not care what feeds it the audio data. If I was at home I would love to try but by the time I get home the drop will be over. Sorry.
HowardCuse the usb cable if they incline one, if not get a usb type b to a & get the Apple camera adapter either the 2.0 version or 3.0 & it’ll plug straight in & should work