A humming or a tone?

Is this sound coming out of your speakers or headphones or where?

It's a tone which comes out of the speaker and headphone when the needle is on the vinyl.

Sounds like you possibly have your source switches (at the top of mixer the black ones)selected to the thru so you're hearing the control tone off the control vinyls, switch those over to the USB and you should be able to hear your audio files from scratch live. Use the thru mode when you are playing traditional vinyl.

Thanks mate that's seemed to have sorted the problem out! 😃