The conection you made is not quite right. This is because the TRS (and the XLR) connectors at the back of the BX8a are for balanced signal. You have to use either this cable
or connect both middle and ground point of the TRS connector at the ground. In other words the ground from the ipod must be connected with ground AND middle ring of both BX8a and the ring of the ipod must be connected with on BX8a TPS tip and the tip of the ipod must be connected with the other BX8a tip. I don't know if you are familiar with soldering connectors, in this case post me back to make a schematic for you with the connections.
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