75-ohm cable is not correct for use with line-level audio, but correct or not, it seems to work. And because of its convenient termination, is becoming the method of choice among installers.

RG6 & RG59 both have the capacity to carry audio, but their loss/ft ratio is constant, and will affect any signal accordingly.

And, unbalanced audio should not travel more than, what is it, 30 feet, maybe 50'? But I've run it over 100' without any problems, even using shielded 2-conductor.

So, making RCA cables out of coax for audio over long distances slightly breaks all the rules, but seems to work. So until it doesn't, keep using it.

Doug @ HomeWorks