The only way you can get a digital output from your iPod is through the Wadia 170i dock - you can't connect the iPod directly to the USB input on your amp. You need to connect the iPod via the Wadia to an external DAC and then by anologue connection to a line input on the amp.
Alternatively, you could directly connect your computer to the A1 via the USB connections and use iTunes to play through your system.
Alternatively, you could directly connect your computer to the A1 via the USB connections and use iTunes to play through your system.