I've got a Hikvision mic that is hooked to the audio in of a hikvision PTZ camera. The mic is external powered 12v and I am using a 12v power supply I had here from past experiments. My problem is that no matter what device I use to listen to it with there is a loud humming/buzzing noise that almost drowns out the birds that are outside. Any help would be appreciated, is there any chance the power supply would cause it?.