correct order from iphone to receiver using airport express


I'm streaming from Tidal on my phone to my receiver through an airport express puck (not Apple TV). Right now I'm connecting the airport with a mini-plug to RCA splitter into the CD port of my receiver. I'd like to connect with an optical cable and have one on order to connect the express to the receiver. Two questions: 

1) Presently I assume that I'm using either the DAC onboard my iphone or the DAC in the airport since I'm sending an analog signal to my amp. If I continue the same order but use an optical/digital cable instead of an RCA will this bypass the DAC in the iPhone and Airport and use the receiver's instead? That would be ideal because then I wouldn't have to buy an additional DAC. 

2) If it's not that simple, I'm assuming that I will need to introduce a DAC somewhere along the path, but where?  If I have to connect the iPhone to a DAC using the lightning cable then that keeps me tethered with wires and I may as well eliminate the Airport right? 

Or, perhaps there's another, better pathway? 
brianpdx
Not sure you can get a direct digital out of an iPhone, or any Apple product.  At one time a few audio companies paid Apple for the input on how to do this - Wadia, Pro-Ject to name a few.  I guess the market was not large enough to offset the premium paid to Apple.
Thanks Miner, that's interesting. I was under the understanding that connecting the iPhone through the Lightning port to a DAC would do it. But, I'm not surprised that Apple would be proprietary and weird.