I have tried two different power supplies with same result. One of them is original Apple and the other one is cheap China model.... Will check with third one when I get the chance
I always use external power for Fireface 400(Because I use it as a stand alone mixer)
I just made a small recording of connecting and disconneting the axoloti plus I took notes of noisefloor of axoloti when connected with power supply and not.
Maybe I am not using right name... There is low hum and hi pitched noise that might be mistaken for crackles.... l
With out power supply noisefloor is really good around -90 db, like G2, Blofeld, Micro q etc. Super great
When the power supply is connected to the laptop the noise/hum floor rises to around -45db.
Heere is a link to a recording of Axoloti being connected to a computer WITH power supply connected which comes in at around -45db.... Dont know if you can make anything out of it.. Anyways here it is