Heres how I did it since there are no off the shelf solutions available to get an aux iput on an older Alpine deck. I wanted an input for an ipod on my 7949, but besides a modulater(all of which are terrible) theres nothing out there. I found a way that will work on any cd changer compatible head unit. What I did was solder 2 rca leads onto the outputs inside the case. In my cha-s614 the wires were marked on the board which made identifying them easy, but I double checked with a DMM and the pinout for the Ai-net connector. Then I put it all back together, I did have to slightly modify(cut) the corner piece for the new rca cable to fit above the ainet cable.
The key to making this all work is to find a way to tell the headunit to activate the input, I accomplished this by making a stereo track of complete silence the length of a cd using Audacity, and then burning that onto a cd. I even went as far as to label that cd IPOD, so when it is selected It appears as if it is actually and Ipod input. I hope this helps anyone else in the same situation.