Coax Digital Out -> XLR Digital Input cable?

Got it. Hope you can get it to work the way you want. 

If you are interested, for a bit more money you could consider a Denafrips Gaia. This is a digital to digital converter and will accept SPDIF in and has AES outputs. It has optically isolated inputs and reclocks the data with an oven controlled oscillator.

I just got one of these a couple weeks ago and I'm very impressed by what it has done in my system. I'm using USB in and i2s out. 

https://www.denafrips.com/gaia

Coax cable provides DIGITAL signals.  XLR cable is ANALOG.  

Never the two shall meet :-)

Coax cable provides DIGITAL signals. XLR cable is ANALOG.  

Never the two shall meet :-)

You should google "AES/EBU"

XLR is a connector type, while AES/EBU (now known as AES3) is the name of digital standard (IEC 60958 type I) that uses 110ohm cable and XLR connector.

Oh no.  Digital and analog confusion again.  Look, the signal is electromagnetic, it does not know if it is digital or analog.  Both types will travel at the same speed and react to impedance the same way.  So let's just close the case on getting a digital or analog cable.  Silly topic.  Now, you can DESIGN a cable for digital or audio applications, but basically you are designing in the parameters of impedance, etc. 

You are splitting a signal, single ended to balanced.  That can work OK. But that will halve your impedance.  Any type of signal has to be matched to that at the source or load.  So you should start with knowing what your source and load impedance is. So if you mismatch the source and load and the signal is analog, it is more forgiving.  Of course you have trashed the signal.  If it is digital all hell brakes loose and if you have a good receiver maybe you can recover and not lose too much data. 

I doubt a straight cable is your answer.  Probably an adapter, but never designed any so can't say.