Balanced connections often do have signal on both lines but symetrical signal output has nothing to do with 'balanced', or noise rejection.
I guess we'll just have to agree to disagree on this one - no problem.
Yes, I've read the Jensens white papers you reference on this subject and I'm afraid I may not agree with your conclusions. Disregarding that Jensen has an interest in transformer sales, I have no real dispute with what they've said. It's rather well written.
Their heavily weighted references to the importance of impedances works toward the resulting use of transformers. Yes, it is important to ensure that you have matched output impedances on your source device or you can upset the level of the (+)(-) conductors. This level matching is what determines the final CMR ratio.
Some of the white paper deals with various methods of overcoming the poor practice of connecting balance to unbalanced and vise-versa.
The practice of using convertor cables that go from unbalanced RCA to balanced XLR usually increases noise in a system by injecting noise into one of the differential receivers from the XLR lead tied to ground.
They show a typical passive method to overcome this problem, but of course you then have to deal with its associated loss of signal or gain reach.
I do have a working knowledge of differential connections and CMRR principles, so believe me when I say that the basic principle of balanced interconnection is exactly as I stated in my upper post. This is a standard technique to cancel induced noise on a line using common mode rejection with differential circuits. It's normally done with operational amplifiers and precision resistors for matching the two channels.
The balanced connection doesn't use a current carrying shield used in single ended connections. It has a standard differential output on the source side feeding a twisted pair of wires that connect to an input differential receiver. That's it. Obviously this sort of arrangement has to be well done with matching input impedances and high quality differential amplifiers and precision resistors for matching the two channels because there is a lot of chance for distortion from a difference amp. If one channel handles the signal differently than the other, distortion will be introduced into the resultant output signal. But, this is a fairly well understood method of transmission.
The reason this principle works is because there is a mirror image on the two (+/-) current carrying conductors that will pass through the receiving ends difference receiver because of the fact that they are completely different (180 degrees out of phase). Any noise riding on the two wires will be the same and won't pass through the difference receiver. This is the principle of high common mode rejection. If the signal on both wires is common to both wires it is rejected.
brucek