I'd like to make an xlr (2 x 3-pin) to 1/4" female adaptor cable for use with my 4-channel balanced beta22. This is so I can try some headphones without having to re-terminate them first.

Is it going to be safe to wire :

left xlr pin2 signal to tip

right xlr pin2 signal to ring

left and right pin3 signals to shaft

?

Don't tie the pin 3 connections together, you'd be shorting the output of two boards together. Use pin 1 as your connection to the TRS sleeve; you might have to open the amp up and add a wire from signal ground to pin 1 on the XLR jacks.

open the amp up and add a wire from signal ground to pin 1 on the XLR jacks.

ok, that I can do.

should I be sending each of the pin3 signals onto pin1's and from there direct to signal ground once they enter at the adaptor cables' xlr connectors ? / what should be done with the pin3 signals ?

No, you do nothing with pin 3; don't connect anything to it. You're only using 2 channels for single-ended, the other 2 are only relevant for balanced, so they don't get connected to the headphones in this situation.

ok, thankyou for your help