On Thu, 4 Jul 2002, Brian Becker wrote:
Just as a comment...balanced is required to have a ground and a shield to be defined as balanced. Of course much of the audio gear can survive if the ground and shield are the same signal, but it is not part of the spec and all major recording studios will utilize separate and distinct paths for the ground and the shield to reduce the level of noise to its minimum.
In the more abstract case "balanced" refers to forcing or guaranteeing the return current follows the same path as the forward current, but just in reverse. - one could use a coax line and still be electrically balanced (as long as the devices at each end do not share a common electrical return) - one could have a paired line with a shield and still be unbalanced (if one leg of the line is tied to a common electrical point) It's not so much the type of physical cable in use that determines whether a line is balanced but how that cable is used electrically and whether there is a common electrical point (usually ground) between devices that might possibly allow some return electrical current through a different cable or path than the forward current. Whenever that happens, the likelihood of noise being picked up through electrical induction is significantly increased. I'll leave the physics explanation out... :)