Using XLR for Phono out

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.)

Manufacturers do it because SE is cheaper (half the number of parts ;-) ). In phono preamps, designers have traditionally used SE architecture because adding the other half for balanced will increase the inherent circuit noise. That would be a good example. The MC pick-up is naturally balanced. Connecting it that way to the primary of an MC input transformer, then connecting the secondary SE is quite common.