Balanced cables

  transaudio

The reason most pros use XLR is noise floor- having a shield that encloses the positive and negative audio cable inside to protect it from outside noise. 

No, pros use balanced XLR cables because of their Common Mode Rejection Ratio - the very nature of a balanced circuit. They don't require shielding to achieve low noise. Unbalanced lines, however, often benefit from such shielding.

 

They don't require shielding to achieve low noise.

This is true- I've used balanced Kimber which has no shielding at all and over 30 feet, not hum/buzz whatsoever.

I'd like to thank @atmasphere and @almarg for participating whenever discussions involve balanced cables / components.

I've noticed a few assumptions that lead to confusion surrounding balanced cables / components. Here's how I generally cut to the chase:

1. XLR terminations on a cable do not (necessarily) mean the cable is of a balanced design. Sometimes the designers design to the "spec", sometimes they get close, sometimes they don't care.
   
2. XLR connectors on a component do not (necessarily) mean the component is of a balanced design. Sometimes the designers design to the "spec", sometimes they get close, sometimes they don't care.
   
3. When designers design to the balanced "spec", things play together with less variance due to the component interactions through the connections (and have less impact through noise that may be injected into the system). Everything else requires much more "trial and error" with regard component matching.

In summary, the value of balanced components using balanced cables (generally leveraging XLR terminations / connectors) designed to the the balanced "spec" are 2 fold:

1. What @cleeds states  - Common Mode Rejection Ratio. CMRR (in overly-simplifed terms) mean when noise enters the signal path, it affects the (+) and (-) legs identically. When the (-) signal is inverted and summed with the (+) signal, that noise magically cancels itself out.
   
2. The input (and output) impedance of the components are sufficiently low (or high, respectively) for generally optimal transfer of signal.
   

@2channel,
+1

Bob