Possible ac line static.

Is there a modem/router anywhere near your stereo? Also light dimmers in your room are a common cause of AC noise.

Or switch mode power supplies (SMP), they can be noisy evil things especially cheap wall wart ones. Also desktop power and lap top supplies.

Just go near them with a portable am radio tuned off station around 600khz, turn up the volume, make sure it doesn’t auto mute because it’s off station, and that’s via the air, imagine what they’re injecting into your house mains wiring.

Cheers George

No router, small comsuck 3x4 cable box.

basement has those gas filled long tube lights.

 Lights off, static still present.

cable tv  wire runs behind rack.

preamp b the issue?Aging B&K pro10mc mc?

What does this mean??

What is AC line static and what does it sound like to you?  How old is your amp and pre?