UR44 + iPad Air + Cubasis = phantom noise on all inputs

I’ve updated to the latest firmware, used the ferrite core and eliminated any other potential groundloops but Cubasis still seems to pick up a phantom noise signal from the UR44.

I does this even when all instruments are unplugged and levels turned down. I say phantom noise because I can’t hear it (but I have cheap monitors that probably won’t deal with those frequencies - next on the shopping list!) but I can see it oscillating between the second and third bars on the fader input levels and it shows on playback.

Is this normal or have I completely missed something? I’m well versed in using old tape-based multitracks with analogue desks and getting track spill, hiss and hum but didn’t expect it from digital audio. :confused: