doesn’t do ANYTHING for C920 Mac mini osx 10.11.2

I get the other end on facetime saying they hear a echo
2010 mac mini OS X 10.11.2 8GB ram 500GB Hybrid Seagate drive (8GB NAND FLASH)
C920 Logitech plugged straight into usb 2.0 port
Sharp 40” LED tv
The facetime video I see is choppy
the other end says they hear themselves again (echo)
this software just blows
Can’t seem to find a web cam that works with the mac mini
oh, and it’s on 1Gbs ethernet connection to 1Gbs SWITCH to 1Gbs port on router to 75+Mbps cable broadband
so this application just blows

philmiami about Logitech Camera Settings