I have been running the Alpine CDA-117 headunit for several months now and I love it. It is everything I was looking for in a headunit. It has awesome Ipod integration via a rear USB input. I use that function with my Ipod for most of my music; however, I wanted to open up to additional options.
(The following end result can be adapted to any headunit with the proper aux adapters)
While this h/u comes with a rear USB input, it does not come with a 3.5mm input jack. It does have the option to add an auxiliary input though. This is the route I wanted to take.
Beyond that, I wanted a dash mounted, flush mount aux input. The Ipod is run into the glove box and I only remove it when I fly or need to update the music, etc. The auxiliary input will almost 100% be used by my Evo 4G cell phone for Pandora and other music, which means it will be unplugged and removed from the vehicle as much as I am....removed. That is where the dash mount comes in.
I found all the parts I needed on Ebay for about $12 total. The first piece of the puzzle was the actual auxiliary adapter for the Alpine h/u. The Alpine brand adapter was about $16. This one is the import version for about a dollar. This plugs in the back of the h/u and ends with female RCAs.
The next piece was the cable that runs between the adapter and the 3.5mm flush mount plug. One end of this cable is male RCAs and the other is a female 3.5mm jack.
The final piece is the actual flush mount 3.5mm jack. The outer end is the female, and the other end is the male that will plug into the middle cable connecting the whole puzzle.
Skipping ahead to having the h/u removed...
I decided that I wanted the jack to be mounted in one of the switch blanks. This location is good for me because it can always be removed without permanent damage done (with a new blank or switch). It is also low enough to keep the cable out of the way.
The cables would be fine to be connected via the RCAs and then tapped together to prevent them from coming unplugged, but I wanted to go for more of a permanent solution and a completely solid connection.
I cut the RCA ends off of the cables and spliced them together; sealed off with heat shrink tube.
Here you can see the aux adapter plugged into the back of the h/u
Everything back together and ready to rock