Mmm...
To get the cute 2in1 hub shipped to France, I must add 13.5$ and maybe also taxes, leading to at least 23$.
I tried my own NON powered 4 ports USB2 Hub (came with RockBand Wii!) and I get the same result as with the SHIFT-STOP bit :
No more "too much power" message but no BeatStep Pro in midi devices of apps.
UNTIL... I switched the 2 USB cables!!
I use from now on the cable that came with BSP on the PC branch of Y cable and moved the no-name-and-highly-suspicious other USB cable to PWR branch.
And it works like this!
(I also add, as you smartly suggested, a midi keyboard -QuNexus- plugged in one of the others ports of my hub with success : The 3 midi ports of the QuNexus immediately appeared in midi devices.)
Now that it works at least, I still can't use it : iPad was low battery and switched off 2 minutes ago
I may buy the battery pack you mentioned on the other thread (unless the new Pocket Operators launch next days
)
Thanks for your answers anyway!