Contrary to the popular belief, popular USB implementation of iPhone/iPod on most devices is not digital extraction, even as it yields better results. Due to closed nature of Apple's policy, very few manufacturers have been able to implement "true digital extraction" from iPod. Wadia for example.
Are you sure? I always thought that if you manage to get audio through Ipod USB, it is digital. I was under the impression that all docks that have speakers or analog out, works on the digital stream with their inbuilt DAC. Ofcourse, there are a few docks that has S/PDIF as well. Many have been successful in taking out digital stream using "camera connection kit". I also believe all ICE HUs which support Ipod direct connection works on digital stream. My JVC does for sure. So I am wondering if they are not digital extraction, what they would be.
BTW, I have been able to confirm several times that my android tab- digital out is sounding much better than my PC.