From the preamp XLR out to a pair of Krell Evo 600 mono ampsTo add to the good comments the others have provided, most (but not all) XLR-to-RCA adapters short pin 3 (one of the two signal pins) to pin 1 (ground). Depending on the specific design of the component, shorting pin 3 of an XLR output to pin 1 may have the following possible results:
1) Damage to the component, eventually if not sooner.
2) No damage to the component, and reasonable sonic results.
3) No damage to the component, but severe buzzing or other sonic anomalies. See this thread for example.
Also, with some designs whose output signals on pins 2 and 3 are floating relative to ground, hum and/or improper operation may result if pin 3 is NOT grounded.
As others have said, don’t do it. Certainly when it comes to XLR outputs, unless a very specific ok is obtained from the designer/manufacturer and you know whether or not the adapter grounds pin 3.