No you do not want to use a hard wired Y cable to combine two outputs,each output is being driven by the other output. Depending on the equipment the outputs could be driving what looks like a short circuit.
Here’s good link to building a resistive isolated combiner, I’ve built them and all the parts can be fit into the XLR connectors.
The resistor values can be increased a little. The 20k resistor can be omitted.
But that doesn’t mean that the negative pins 3 of the balanced outputs are practically hanging in the air?
Surely they’re connected to each other on the back of your board - and possibly also to the pins 1.?
Yes they are. No issue for a stereo headphone use with XLR up to 5 meters (didn’t tested more but of course interference might occur as it is unbalanced)
That’s pretty strange, though, since each output is practically only connected to one pole.
It’s a bit like connecting an electrical device only to the phase and somehow leaving the rest to the protective conductor. )
But anyway: Using something stereo wasn’t the topic here, but rather converting stereo to mono in a simple way possible.
As far as I can see It won’t do the trick for any of the EFX outputs you are using bcause they also output in stereo but will sum to mono if sent to one of the Aux Outs.
