Trying to connect an unpowered mic to the PTZ and not having any luck....Connected the ground wire from the mic to the black ground wire on the PTZ....Then the Audio wire from the mic to the white "audio in" wire on the PTZ...All I hear is a loud buzzing noise. Does Dahua not handle unpowered mics or am I doing something wrong? For the record, I tried the same mic on the Huisun mini-ptz and the audio works fine.