Going in directly to Marantz SA 8005 CD by passing the iPhone 6 DAC

I’ve read on the internet that this can be done but I can’t get it to work. I bought the iPhone camera adapter and a male to male USB. The error message under DAC on the CD player says unlock and if I switch to USB it says no device. I can access TIDAL  Hifi through my phone by not using the camera adapter and some songs sound ok but most are not as good as CDs played off the Marantz. I’ve tried downloading a usb upgrade from Marantz on my iPhone but I can’t unzip it and don’t know for sure how to. I’m not too computer  adept. I tried an unzip app. I’m going to be laid up from surgery and just was trying to enhance my musical enjoyment. I called Apple and Marantz. Apple says it’s not official to use the camera adapter in that way and Marantz says it’s an IPhone issue. I got my son an Audioquest dragonfly and in the instructions they point out the camera adapter as necessary for an iPhone hook up. Is there other DAC s out there that are more iPhone friendly? And how much money are we talking about to significantly upgrading the internal iPhone DAC to a stand alone DAC? I assume the DAC in the Marantz would be. Thanks