Balanced cables


Do different brands/levels of balanced XLR ended cables going to and from differentially balanced components make a difference?
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From a high end PRO perspective, there is just as much difference between high end and low end XLR cables as there is in high end and low end unbalanced RCA cables.  The cheapest XLR cables are absolute crap and roll off the top end and make the low end muddy, midrange cloudy- just like unbalanced cable. 

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.  In high density cities like New York, LA, Dallas, etc RF is everywhere and can make noise that shows up in the audio of an unbalanced system.  If a RF tower is near you that can sometimes create issues.  

Having a complete system balanced is key in high pressure environments, like a recording studio.  All you need is someone drive by with a big output RF device and your recording would be completely ruined.  This used to be common when CB radios where popular.    

Some like unbalanced better because HOW many designers balance their audio devices inputs and outputs can affect the sound quality of an audio device or signal chain of multiple audio devices.  

Some balanced cable is a spiral shield, and not 100% coverage of the audio cables within.  100% braided shield is the better method for RF protection but it can make the cable less flexible.

Electronically balanced input/output stages vary in sound quality depending on design.  THAT corp designs a great electronic balanced stage called OUTSMARTS we use an output stage of a mic preamp.  We still use a Jensen transformer on the mic input.   Transformer vs electronically balanced outputs do sound quite different.

If you run balanced cable and balanced devices and then insert one unbalanced device in the middle, the system is unbalanced at that point and any noise present is now in the audio path regardless of balancing later.  The shield just protects the audio cables within.  Remove the shield or reduce its coverage and the noise is back.  
       
High capacitance cable can be a problem, especially when used with a microphone.  The top end is affected by this build up of capacitance over its length.  Make sure you read the cable specs and avoid this high capacitance cable.

XLR cables in balanced rigs can be run long lengths noise free.  That does not mean they sound good over long runs.  There is HF loss or at least changes in HF audible with longer cable runs.   But in some cases like broadcast, it does not matter so much, the noise avoidance is the goal. 

Brad

  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.
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