I'm looking to run a line level out the tape mon. output of my living
room amp and into the tape mon. input of an amp in an adjacent room.
To do this I have to pass cable through one wall, the rest of the
cabling will run around the baseboard of the rooms. I tried using
speaker wire with RCA jacks on either end but it picked up too much
hum. Can anyone recommend to me what kind of cable to use for this? I
read somewhere that CAT 5 computer networking cable works well for
this, has anyone tried that?

This doesn't need to be a super best high end sound quality kind of
thing, I just want a decent, hum-less signal.