Here's a cool trick for balancing an unbalanced line. You want to run a signal from, say, a keyboard 50 feet away to your mixer. The unbalanced line is too noisy and you either don't have a balancing transformer or you don't want to use one (many people think they affect the sound adversely). It's not hard to make a pseudo-balanced line from the unbalanced output of the keyboard. Make the 50 foot run with a standard mic cable. At the end where it plugs into the keyboard connect a precision potentiometer pin 3 (cold, or "-") of your XLR and ground/shield (pin 1). On a TRS this would be between Ring and Sleeve. Connect pin 2 (or Hot) as normal. On a TRS this would be the tip. Often it is easiest to just make up a special cable you can connect in line with the pot on it. Turn the equipment on and turn up the gain on your mixer until you hear a good amount of hum and line noise coming in from the keyboard line. Turn the potentiometer (which will change the resistance between pin 3 ("-") and ground) and you will hear the hum and noise level change. With some careful work you should be able to find a "sweet spot" where the hum is minimized. If this is a permanent installation you can then substitute a precision resistor in place of the pot. What you have done is put a resistance in parallel with the output impedance of your source (in this case a keyboard) from pin 3 to ground that matches the pin 2 relationship. Normally, on an unbalanced line pin 3 would be shorted to ground, and you give up any CMRR your mixer's balanced input has. We've heard this make a dramatic difference in some circumstances. In our Sweetwater Studio all unbalanced devices are connected to our Euphonix console in this fashion. Remember you must use precision components here, as minute changes in value will significantly effect the signal to noise ratio.