Geez, I'm afraid to even ask if you can plug an external hard disk with my music collection into the SRX USB drive. I might bring down the wrath of the whole forum on me.
Seriously, what is the difference between a thumb drive, hard disk, and an iPad? They are all storage units and should work equally. If the iPad is not recognized as a storage unit, then there must be something in the iPad blocking the connection and it's usually the power charging system. I've seen this with the iPad and other mp3 players. Even though they have USB jacks, they will not charge because they are expecting more milliamperes through the USB.