CollettesKaraoke

i was reading some of the chat & we had some hum noise coming through our system when we tried to isolate it it was coming through the mains power outlet where we were connected to a TV & aerial was plugged in once we took the aerial plug out of TV no hum I have been running a Karaoke show so had to access Pubs TV which had an interconnecting AV & aerial line into the TV we were using we had a HDMI