Logic Pro X - Audio tracks have strange screech and static sounds

Hey team,

I have been using Logic Pro X for forever but lately when I try to record vocals, the audio track on Logic has a screeching and buzzing sound that I can't get rid of. You can hear it live and in the playback. I have tried a different interface, cables and microphone so must be something on Logic. I have also tried different buffer sizes but no luck :( I have an older Mac (2011) so am unable to update the software. Please help! Thanks :)