Using XLR for Phono out

Lewm, of course I was refering to the use of transformers as an input device. That was the context of the discussion. Even when used as the input for a SE (balanced to SE conversion) you still have high common mode rejection. If you apply the same signal to each leg of the transformer primary, as in common mode noise, you cannot generate any magnetic flux in the primary and thus no signal. This would be different if you were to ground one leg. A tranfomer "naturally responds to a differential signal.

Wow, Thanks again Ralph for a more complete explanation and understanding. I
must have had my recollection of my conversation with Jim White confused
somehow and that explains what Lewm was trying to tell me which I misread .
Sorry folks for the added distortion, I still have a few things to learn.

Happy Holidays Ralph and AudioGon Friends and as always...
Happy Listening!

As far as I know, in SE mode, one side of the input transformer IS grounded. That was my only point. You need to input a balanced signal to a transformer and take its output as a balanced signal in order to realize CMR. I am sure you know this; I was trying to clarify the point for others.

Lewm, if you feed a balanced signal to a transformer and the primary winding is either "floating" or wired balanced (CT grounded), you will have CMR even if the secondary is wired SE. If the signal is the same on each leg of the primary (common mode) the potential difference is zero! No magnetic flux, no signal transfer, therefore high CMR. The primary does not care how the secondary is connected as far as CMR is concerned.

Cool. But I was not totally wrong; you need to feed a balanced signal to the primary. I don't know why one would want to convert a perfectly good balanced signal to SE, except if you are a transformer-phile. (I'm just kidding; you probably have sound justification for this approach.)