It’s very unlikely, Ozzy.
In the case of analog outputs, some designs drive XLR and RCA outputs from separate output stages (i.e., they individually buffer them), and some don’t.
If they do, obviously connecting both would not cause either of the connections to have an effect on the other. (Aside, that is, from the possibility of introducing a ground loop and its negative effects, assuming the other ends of both cables are connected to a single component).
If the two outputs are not individually buffered, the signal provided to the RCA connector is probably the same signal that is provided to one of the two signal pins on the XLR connector. Connecting them both would do nothing for the other signal on the XLR connector, while resulting in at least a slight imbalance in the impedances of the two signals on the XLR connector, thereby degrading the noise rejection that a balanced interface can provide, at least slightly. Also, depending on the output impedance of that component and on the total of the capacitances of both cables, upper treble rolloff of whichever signal is used by the destination component might occur to some degree, and sharp transients might become more sluggish.
In the case of digital outputs, coaxial S/PDIF and balanced AES/EBU outputs would certainly be individually buffered, since their output impedances have to be different. So connecting both would not accomplish the same thing as doubling a cable, which as I’ve said I don’t recommend anyway for digital cables.
Zephyr24069, thanks for your comment.
Best regards,
-- Al
