An excellent paper on routing cables to avoid interaction and noise injection.

Or you could just keep them all a few inches apart, and at 90 when this isn't possible. 

There. Now THAT was a pretty easy read!😂

@millercarbon -  if you want to scrape  the last vestige of hum out of your system, you will need to do a LOT more than "keep them all a few inches apart."   You do need to read the paper if you think that is all there is to it.

Not really. I scanned enough to realize nothing new. I also realize there's people do nothing but post glib uninformed comments. Mine is glib, but informed. I know there is more to it. But if you want to help people without taking up a whole afternoon boring them to tears with techno jargon, route wires a few inches apart and at right angles when space isn't possible.

     Was there something to read, in the original post? Didn’t show up, here.

     At any rate: if one considers the low voltages/currents we’re dealing with, as regards the typical system’s interconnects; the Inverse Square Law works nicely, with a few inches distance, when faced with parallel runs.

     AC cables and interconnects (particularly so, if unbalanced) may prove another story; especially, if the interconnect feeds a higher gain circuit (ie: phono).

     Crossing cables of any kind, at 90 degrees, is sometimes the only option and will typically avoid induced currents.

               http://hyperphysics.phy-astr.gsu.edu/hbase/Forces/isq.html

     https://www.thepodcasthost.com/equipment/cable-crossing-bad-thing/#