If aftermarket premium power cords work, why won’t short runs of premium XLR cables work?


I have followed many threads, where people swear premium power cables greatly benefit your sound.  I haven’t decided, as the last time I tried a power cable was twenty years ago.  I used a Transparent power cord and was on the fence.  If adding a power cable improves the sound and it’s only the last few feet of your voltage source, what would make extending a premium XLR cable any different?  If I understand the argument, per se, the premium power cord acts as a filter.   XLR cables are mostly unsupcetable to outside interference.   I’m sure I will be versed here one way or the other.
handymann
In my experience, different XLR do sound very different. I had Kimber Hero, Cardas Parsec, and finally Kimber KS1116. Each a big jump in price, and a good step up in sound.  
If this was the case, then the associated gear didn't support the balanced standard.
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I am sad your confidence in ’theory’ precludes all fact.
@elizabeth Its not theory. I've been doing this a long time, and I've seen plenty of cases where one cable sounds better than another, including balanced.

The thing is though that most high end audio products don't support the balanced standard. They might be fully balanced, but fully balanced and supporting the standard are two different things. The standard is there so that cables don't sound different from one another (amongst other things) but supporting the standard is hard so most manufacturers don't do it.

As a result, you have the experiences that you have, because the gear you used didn't support the standard (also known as AES48; Audio Engineering Society File 48).

You can read more about this here:
http://www.atma-sphere.com/Resources/balanced.php