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Have you actually tried this with a simple (unbalanced) cable like a guitar cable? I would have thought it would be as good if not better. The way you have it set up, it's not actually doing balanced audio - for that you need the shield grounded, and the two inner conductors carrying mirror-image signals of each other which get subtracted from each other at the receiving end, thereby cancelling out interference. None of the conductors should be connected to each other, and you would need considerably more circuitry to achieve it. Random google hit with more info http://www.aviom.com/blog/balanced-vs-unbalanced/
How to make an Arduino from scratch
Electronics Building Tips ( in 21 Plus Steps )