Question Low buzzing noise when off

[crashcity]

Hey guys just got me a new psu, Seasonic Focus 80 gold+ 650W, and when my whole pc is off, i can hear a small/low buzzing noise from the psu only if i put my head really close to it. The noise stop if i turn the psu power button off, but will come back if i turns it on.

Is this normal? I can return if it its not. Any helps is appreciated

 

[crashcity]

When my pc is off, I can hear a really small, high pitched noise comming from the Cpu/cpu fan area. My psu also make small buzzing sound but that’s another story.

The pitch noise stop if I turn off the psu switch, but will come back if i turn it on.

Any thoughts on why this would be happening?

 

[crashcity]

The small high pitched noise stops when i unplug the 24-pin connector but will continues when i plug it back in. So can i assume that the mobo is at fault here? I also read around and found out that the small buzzing from psu could be from the +5vsb but not so sure.