Mackie ProFX8 USB noise

Hello everyone. I have a problem with my mixer.

I've bought a new condenser mic to record acoustic guitar - AKG Perception 170. I was about to test it but noticed that there was annoying noise. Firstly I thought it came from the mic, but then I disconnected the mic and muted all the channels and started recording. There was a noise for like ~52 db.

So I think the problem is with USB connection of mixer and my laptop.

So, my question is: is it supposed to be like that? I mean the level of noise. Because when I record a guitar, I can't get a clear sound that I want to and that a mic can give me. I there any way to fix this?

Thanks.

I got a profx12 and I haven't had that issue. Not that its the exact same model but I haven't had issue with it in that respect.

Have you tried plugging it into another USB port or another machine to see if the same noise?

Have you "zeroed" the mixer as described in the manual?