Mic buzz when recording vox

Hi all.

I use Logic Pro x on my iMac, with a condenser mic going through my m-audio fast track pro.

I'm having the problem that when I have a vocal track and click record, there is a constant buzz/fuzz/hiss in the background. Nothing super loud, but certainly loud enough to hear it very clearly.

I have tried a different xlr lead, moved the mic around, unplugged guitars, used compression etc yet nothing makes it go away. I am not a pro so is there something more I can try?