Strange that the two channels gave different results. Not sure how to explain that.
Just to confirm that the correct pins were measured, pin 1 of each of the female XLR connectors would be the pin closest to the right side of the connector, when viewing the connector from the rear of the amp.
Given those results, additional measurements that might be useful to know would be the resistance between the ground sleeves of the two RCA connectors, and the resistance between pin 1 of the two XLR connectors.
In any event, I would still expect connecting the black wire to XLR pin 1 to work, although using the right channel XLR connector seems like the surer bet.
Best regards,
-- Al
Just to confirm that the correct pins were measured, pin 1 of each of the female XLR connectors would be the pin closest to the right side of the connector, when viewing the connector from the rear of the amp.
Given those results, additional measurements that might be useful to know would be the resistance between the ground sleeves of the two RCA connectors, and the resistance between pin 1 of the two XLR connectors.
In any event, I would still expect connecting the black wire to XLR pin 1 to work, although using the right channel XLR connector seems like the surer bet.
Best regards,
-- Al