Why the big difference in feedback/noise between iPod and iPad?

[festeringheap]

I have an iPod 4th gen (iOS 6) and an IK iRig guitar interface (the one that plugs into the audio jack).

For the most part, I have had no issues with that setup and can crank up the volume (if I so choose) and there is no feedback. (I mostly use Ampkit)

I am borrowing an iPad 4 (iOS 7), and with the same app(s) and the iRig, I am experiencing feedback/ noise and hiss at less than 1/2 the volume.

Is there a difference in the way the two devices handle audio?

Or is there a setting somewhere I am overlooking that should be turned on (or off)?

Baffled. Any help would be greatly appreciated!

(I am wearing headphones when I record)