Mtp av USB causing a hum?

[jian]

I' m wondering if someone has any experience with this issue:
my mtp av USB is causing an audible hum in my soundcraft compact 10
mixer. I have a rack unit about 3 ft tall with my mixer on top of the unit and the mtp
on the top rack. When I power the mtp on I can hear a hum in my
mixer through the cons and monitors. When I put the mtp at the bottom of the rack, the hum is not
heard.
I hear an audible hum in monitors and in cans when my compact 10 mixer and mtp av USB
are close together in my rack.

I had tried to trouble shoot this issue by putting different rack units
under or on top of the mtp to see if the humm can be duplicated.
I do not hear humm with my 8 pre or my 828mk3.
The humm only occurs when my mixer and the mtp are close together.
When I put the mtp at the bottom of the rack far away from the
mixer the hum disappears.

I spoke with motu tech who said I should turn off unit and switch
red voltage switch to 220 and back to 110. I did this and the results
were the same. Motu also said it might be a blown fuse. I tested the
Fuse and it seems to be working correctly. Any ideas what's causing this?
Thanks

I have nothing plugged into my mixer or the mtp and I still hear a humm
when they are close together. Any ideas what might be causing this?

Thanks for your help