I'm very interested in the Arduino based pre amp. Do you have a page with your design that I can study? I was thinking about maybe integrating a Lightspeed Attenuator.

Most of all, I'd like the pre amp to automatically turn on the power amp (currently a Gainclone) when a signal starts coming in from the connected Airport Express.

http://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Att...