Arrangement of components on rack

Now and again -- though not often enough, probably -- I spend some time unhooking and unplugging everything in my system, dusting the works, and then setting it all back up again. Makes me feel better, and it seems that the simple act of unplugging and then reattaching cables and power cords etc. improves the sound, too -- if only in my mind.

As I'm getting ready to do that now, I just had a thought: Is there a generally accepted arrangement for components sharing a rack? What I mean is: Are there components that ought be placed close together and those that should be better spaced out? My power amp sits between my speakers, with the rest of the gear over on the side wall.

I've got a turntable, so that takes care of what goes on the top shelf. The other components: A preamp, a separate phono preamp, a CD transport and DAC in one box, a Bluesound Node streamer.

With all else equal, should, say, the phono preamp and the preamp be near each other? Far apart? does it not matter? I've generally just kind of plunked things down and gone from there -- and haven't experienced too much trouble -- though some years back when I had the preamp (the main one, not the phono pre) up close to the turntable I had a bit of hum, so put the preamp on the bottom shelf and have continued to do so.

Still, as I got to wondering and am set to get to work on this soonish, I thought I'd ask if there's a generally accepted way of arranging things.

Thanks very much.

-- Howard