after tinkering a couple of hours, I've got the AirPi working with my Logilink UA0053 USB soundcard. It works very well! For everyone that wants to save the time, I've created an image for a 4GB SD card.
The image is based on Wheezy and configured so that it has:
- SSH enabled
- User = pi
- Password = raspberry
- locale = en_US.UTF8
- timezone = Europe.Berlin
It has auto login for user pi enabled
It is configured to use the USB audio Logilink UA0053 soundcard http://www.logilink.eu/showproduct/UA0053.htm
It's broadcast name is AirPi
Write the image to an 4GB SD card with Win32DiskImager.
Plug it into the raspberry and hook the raspberry up to your network and Logilink UA0053 soundcard and soundsystem. It'll work like a charm on iOS 6.
The files can be found in my public Dropbox.