AV cables iPad2 vs iPad3 I use an extension cable with my iPad2 to connect to an external amplifier with a built-in Dock.  I have recently purchased an iPad3 (awaiting delivery) and was wondering if the cable will work with the updated iPad, or do I need to procure one specifically made for the iPad3.

The cable supports AV, so it's not just a matter of charging/syncing.
It sounds like you mean 2nd generation iPad vs 3rd generation iPad, both of those models do use the older 30 pin connector.  

3rd generation isn't new tho so maybe you mean iPad MINI...   the mini 2 and mini 3 both use the newer smaller lightning connector.

If it does go from 30pin to lightning tho, apple does have 2 different style of adapters avaialble. Here and here.