Can iOS-devices take sound in and send to Airplay?

I plan to find an old iPhone to make my record player connect to Airplay. Is that possible? What I want to do is to take stereo line signal and "input" it into the phone and then playback it on the phone to an Apple TV. Is that possible? What hardware do I need to get the stereo signal into the phone and what software would allow me to redirect the in-signal to Airplay?