ioDock outputs no audio from iPad 1 or iPad 2


I recently purchased a Alesis ioDock 1 , but I'm having a hard time getting it working.

I'm trying a first-generation iPad with iOS 5.1.1. When I plug it into the ioDock, it starts charging the iPad, when I go into settings -> general -> about it shows the ioDock as being detected, and I have firmware 1.07.

However, all sounds come out of the iPads internal speaker.
No sounds ever come out of the headphones or main outputs on the dock.

I've been trying to find the setting where I can tell the iPad to use the ioDock as the audio output but I cannot find it. Is there some setting I missed?

Thank you,
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