mic hiss noise when using ac adapter or external monitor

[tdi]

i have a problem with a9ii when using usb-c power and external monitor ac powered, i get very bad interfence noise and hissing from external microphone plugged in to camera. 
i have to unplug both usb power and hdmi cable before i get clean audio again. i think the monitor or its ac adapter (feelworld 759) is the problem here? 

i can use external recorder. But is there any real solution? And does anyone else have this problem? 
Sorry for bad english