The source impedance is between 2 & 3 as is the load impedance. Ground is not a signal path with balanced lines. Often the lines have no relationship with ground, so there's no point in trying to measure one.
On another note, maximum power transfer occurs when Zs = ZL. There's nothing old or new about it, it's just a fact
On another note, maximum power transfer occurs when Zs = ZL. There's nothing old or new about it, it's just a fact
You are correct, the load impedance is between 2 and 3. This is not the issue of what makes a balanced system. If I float the signal on 2 and 3, and have no intentional connection to pin 1, the system is balanced because the impedance from pin 2-1 is infinite, and the impedance from pin 3-1 is infinite. The impedances from each signal pin to ground is the same (infinity), therefore the system is balanced. This helps with noise rejection when a differential/balanced input is used.
I can do the same thing but have each pin (2,3) connected to ground (pin 1) by means of 100k resistors. Same impedance to ground, therefore a balanced system.
If I tie one of my pins (say pin 3) to pin 1, I still get the same signal between pins 2 and 3, but I have now unbalanced my system because the impedance from 3-1 is now zero, and the impedance from 2-1 is not. Essentially I have a traditional RCA type cable, not a balanced cable, even though XLR plugs might be used.
My eureka moment was realizing voltage balance from signal to ground has nothing to do with being a balanced system, it's the impedance balance to ground that makes it balanced and gives me the benefits.
You were correct.
http://www.jensen-transformers.com/an/an003.pdf
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