Hi people 
I need some opinions!
We are in the late stages of developing our product.
Right now we have 10 units out in the wild being used by live musicians and studio musicians.
Everything has been going very well and we are getting a lot of good feedback, however 1 tester has a problem.
They are getting strange background noise/interference when using a particular power adapter.
Our device is USB powered.
After testing a bunch of different power adapters and power extension combinations i am able to reproduce it with 1 particular adapter.
I understand that this is something to do with a ground loop or a noisy adapter.
I did so reading and apparently there are components that i can add to the USB power input on our PCB that will filter/clean the incoming signal.
My question is this: Can i really design our PCB in such a way that we avoid all external ground loop and noisy power issues? And if so, is it necessary or is it normal to just tell people that they need to use a power setup that is not noisy?
Many thanks for all your input and sugestions!
A little more context: the noise is more than the usual noisy USB background noise, it’s actually in sync with things happening on the board, like pwm and I2C signals. Normally the board is very quiet and works perfectly, it’s just with certain power supplies that the noise is audible 