Building Balanced XLR Cables

Mr. auxinput

XLR should be by STD. No exceptions. Salt and pepper are from another recipe.
I used, built, tested and opened XLR cables. Many for the VOA (Voice of America) projects I was involved (including a winning bid for a station proposal. I wrote book No.4: Audio and time base sub system).
As a part of that rol, we had an Audio expert from the TV broadcast station in Jerusalem. None of your ideas was Kosher.
Powering a mic?
The XLR cables are not for mics. They are for interconnecting home audio equipment.
I would put more attention on the connectors and pick Nutric.
Swiss made, the best in the industry.
Adding a wire (except the shield) is never used in unbalanced (RCA) interconnects, because of the ground loop problem. Why to use it with XLR?

The 4th wire is not for powered microphones.  Powered microphones use what is called "Phantom power".  This is DC voltage that is applied to the signal wires (pins 2 and 3).

The 4th connection on the XLR plug is connected to the equipment chassis/ground.  This can actually be different than Pin 1 signal ground (which is a common/shared ground for the analog circuits), but not necessarily a different connection on all equipment.

Then tvad they are not balanced. Pin 1 has a shorting contact to the XLR housing. There is no forth ground. The proper wire is three conductor. The forth wire is there I believe for powered microphones. Any interconnect without a proper shield is asking for it.
You hook the shield up to pin one and leave the third wire unused at both ends. You use a floating shield in power cables. You are floating it to prevent ground loops. 

ah, just re-read your first post.  If you have a braided wire shield, I would solder that to the "shield" connection on the source XLR plug (typically a female plug).  If you have a "floating" braided shield, it tends to create capacitance and reduces high frequency response in the cable.

I would take b4icu's suggestion with a grain of salt.  It may be true in some specific circuits, but not all.  See this guide:

https://www.ranecommercial.com/kb_article.php?article=2107

The shield connection on the XLR is basically connected to chassis/ground.  This may be completely different than pin 1 "signal ground".  If you have a cable that has 2 conductors and a braided/foil shield, you can connect the shield to "pin 1".  This is common shared signal ground and may be required in some audio circuits.

That being said, I have have had great success in making cables that use three 20awg solid-core conductors in a braided configuration for pins 1, 2, 3.  I don't connect anything to XLR shield/chassis.  This is very similar to how Kimber Cable makes their interconnects (but they use stranded conductors).

Hi

XLR cables should have two conductors and a shield. NOT 3!
Do not use the 3rd conductors for GND.
Use the shield.
Shield is significant to protect from EMI/RFI. use it as GND.
Two ground lines (3rd wire and shield) may cause a ground loop and add hum.
Not to say it is not the standard XLR.
XLR (Balanced line) is a long lasting standard, used in so many applications and configurations.
It works.
Why change?
Just because you purchased the wrong cable with a 3rd conductor?

Thank you!