audio dac design question

[Termanater13]

I'm looking to design an audio dac for use with an xbox and my computer. I know there are many options out there but non of them work the way I want. since I can't find one that will work I want to learn how to make my own. I have an idea on how it should work but I do not have any idea where to start, any ideas?

here is what i have to start.

• I want 2-4 TOSLINK in and a way to make sure i an select which one i can hear.
• chat for the xbox via a 2.5 mm jack and a switch to make to change it to usb for pc use. I  should be able to power it via that usb cable.
• finally a way to mix in an auxiliary source.

I  do realize that getting this done will take some time and may not work the way I want on the first attempt, but as, ong as im learning that will be fine.