Balanced cables

When running mic cables in my distant past, of 100m or more balanced was the way. And transformer balanced , too.
From a low impedance (100 ohms ) would keep the system quiet even after crossing and running alongside hundreds
of power cables.
IC balancing was cheaper but not as effective in industrial use.

In my experience moving to balanced from single ended prodiced a slight increase in articulation, most noticeably in the bass.

Through my many years being in the audio business, and listening to an even greater extent I always return to unbalanced interconnect cables for betters sound. Fortunately my Audio Research amplifiers and line stages have provisions for both so it makes a good test. I've done nearly all of my A/B testing using the same brand XLR vs. unbalnaced (RCA) connectors.

The Cable Company in Ohio has complete charts of those mathematical values from each high end company for their amps and preamps. If you go into a broadcasting-recording supply house and buy inexpensive cable that matches the value numbers of those components you will be blown away at the performance of your gear."

I didn't want to say anything at the time, but this is so wrong in so many ways. TheCableCo. is not in Ohio, not that it matters much, but this falsehood sets the tone for what follows. I can only hazard a guess that the "values" he mentions pertains to output impedance and input impedance but those "values" have nothing to do with matching cables to components. People say all kinds of weird things on the internet and it is best to just smile and ignore. I have just broken from that wisdom. 

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