Quote:
Originally Posted by dhaen
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.
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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.
Quote:
Originally Posted by Key
Can someone else explain what I am talking about please? Because I am not even talking about voltage or power here I am talking about rejecting interference and I don't think dhaen is getting that.
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You were correct.
http://www.jensen-transformers.com/an/an003.pdf
Last edited by zigzagflux; 29th December 2009 at 11:17 PM.
Reason: added Jensen link
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