issue with Loopy HD inside AUM or AudioBus with USB audio interfaces that use 48KHz samlerate.
don't know if you are aware - but there are issues with using Loopy HD inside AUM and IAA apps - when using a 48Khz interface. I've come across this - which causes crackling and makes the interface unusable when using loopers such as Loopy in this fashion.
The HELIX - connected by USB - defaults to 48KHz and the only way normally of switching it to 44.1 is by means of a DAW in a PC or Mac. But when interfaces such as the HELIX or others is connected DIRECTLY to an iPad the samplerate is fixed at 48 and there is no way from the interface itself from changing the rate.
its worth your time looking into this - as not only the HELIX operates at 48 over USB but also older Line 6 devices like the Pod HD range.