https://community.native-instruments.com/discussion/comment/221041/#Comment_221041
Since bickering got the old thread locked I start a new one.
I solved the hum!!
If I plug a USB-B cable into M+ while it is mains powered the hum disappears!!
Take the USB cable back out and the hum starts up again instantly.
I do not want to power it by battery bank, nor do I want to keep a USB cable attached to fix a hum. (MK3 is cheaper if that's the case).
So is this problem fixable with a better quality power supply? If not if has to go back for a refund. There is definitely some kind of grounding problem. I hope it isn't with all facelift M+ units.
I am in contact with support but I want community input also.
Thoughts? No fighting please :)