If the component with XLRs is IEC-compliant use pin 2 for all signal wires and send two ground wires each to pins 1/3.
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Depends whether you're using transformer based gear or not.
W/tranny based gear, use a tiny piece of wire across pins 1 & 3 and run that to the shell of the RCA. Pin 2 will go to the center tip of the RCA.
With non-tranny gear, pin 1 to the shell and pin 2 goes to the center tip of the RCA. Leave pin 3 open.
This held true on my gear using a fully balanced amp & CDP w/single ended passive. The cable with pin 3 open goes from XLR female out of CDP into RCA at pre. The cable w/wire across pins 1& 3 goes from RCA out of pre into male XLR at amp.
I originally made the cable from the CDP w/wire soldered across pins 1 & 3 but got a hum through the spkrs, so removed it & the hum went away.
Both cables are non-shielded.
Additional information courtesy of Jon Risch here
Caution against running the ground to pin 3. This shorts the negative pins of the right and left channels, which were never meant to be shorted together!
If you're lucky, this will only cause mild distortion...
Instead, run a resistor between pins 1 and 3. The value depends on the citcuit. Try 10K for transistor amps or 100K for tubes.
I must have gotten lucky with the preamp/amp combo. The preamp and speakers have been in my system for a while, but the amp is a new addition and I'm just not hearing the distortion. With a transitor amp it should have been wired ground to pin 1 and a 10k resister between pin 1 and pin 3 then right? How about going from a balanced crossover to a single ended transistor amps, would I wire the female XLR the same way with a resister between pin 1 & pin 3? Thank you for the help.
Going from balanced to RCA you would do just as you say. Terminate pin 3 to 1 with a resistor, depending on the the load at the destination (which "looks" from pins 2 to 1).
I'd try and match that load, so the balanced stage sees a balanced load. Not always a necessity, since some equipment just use an inverting buffer for the negative output...
With that kind of equipment, my question would be: why bother?! :-(