Hey Guys,
While there is certainly a lot of dispute on right and wrong ways to handle a balanced to unbalanced connection, the common versions I see are:
Pin 2 >center of RCA or tip of 1/4"
Pin 1 >shield (shell of RCA or Sleeve of 1/4")
Pin 3 >shield (shell of RCA or Sleeve of 1/4")
When taking a transformer isolated output (ex: EAA PSP-2 pre-amp) to an RCA, it is common to float Pin 3 on the XLR end.
I have never seen a case where pin 2 and 3 were shorted (ie. connected to the hot center pin together). Remember, they are out of polarity with each other and would cancel to near silence.
In installed sound systems, landing shield to pin 1 on xlr and to shell on the RCA is a point on unending argument. Some like to land it on both ends, others argue vehemently that it should only be landed on one side or the other. This is equally true in XLR>XLR balanced connections as it is here.
The papers of Bill Whitlock, Jensen Transformers, provide fantastic insight. They are available at
www.jensentransformers.comI hope this helps.
Marc