Why won't my iPad work with my devilsound DAC?

I have an iPad that's running regular iTunes. I tried to run in into my preamp through my devilsound 2.1 DAC. I get no sound at all. iPod doesn't work either. I used iTunes from my HP mini laptop and it works fine. What's gives? I bought the adapter so I can link the lightning usb cable from my iPad and iPod to the devilsound USB cable.
Any ideas? I'm new to the whole iTunes thing, so this may be simply operator error. I appreciate any ideas
Thanks