Couple of questions. First its been discussed a small bit here but are there any USB noise filter that actually eh, work? I have a hifimediy ground loop isolator that gets rid of the measurable hum on my odac but the Mobius is incomparable (it also doesn't work with a loaner jitterbug). The Mobius like the odac seems somewhat picky about usb port quality. Second did anyone else get a faulty USB A to C cable? I have audio cutouts with the supplied one. Fortunately the one that came with my Nintendo Switch works fine!
Mobius itself does not suffer from ground loop problems as long as you do not connect USB and analog Aux at the same time.
Mobius does produce a hum signal if it is not connected to ground at some place while being charged through a lesser quality power source.
The problem originates from the fact that, as long as there is no ground connection, ungrounded (2 prong connected) switched power supplies produce a static voltage of 50V to 100V AC (relative to ground potential) at line frequency (50 or 60 Hz depending on your country).
Now everything connected is polluted with this relatively high AC voltage.
As the internal drivers of mobile's are single sided, they react on this pulsing voltage like electrostatic headphones.
The very light diaphragma is attracted to other metal parts inside, in the rhythm of this pulsing static voltage.
This does even happen if Mobius is switched off, because it's not something that's amplified inside the headphones electronics!
I completely solved the problem by grounding the USB A (outer shield of the plug) side of the charging cable of my iPhone, where Mobius is connected througt the Apple CCK.
Regarding the supplied USB A to USB C cable, it's not of the highest quality. To make it work reliably with iDevices, I had to use a tiny bit of contact cleaner on the USB A side. If you want to do that, do not spray the contact cleaner into the cable, use a wooden toothpick to apply a tiny bit on the contacts.
The problem I had might even be connected to the fact that the charge current of Mobius is at the edge what the tiny 5W Apple power supply is capable of.
I had no problems when using the bigger 12W iPad power supply.