NEVER short pin3 to pin1 on a balanced XLR output.
@danip If the equipment supports the balanced line standard then this should be no worries at all. But it is worthy to note that most high end audio equipment and a fair amount of studio gear doesn't support the standard.
The standard (AES48) calls for the outputs of an XLR (IOW, male XLR) to not reference ground. There really aren't many ways to do that! An output transformer is one way, and obviously if one side of the output secondary is tied to ground (pin 1) its no worries whatsoever. Our preamps are another way this can be done as they have a direct-coupled (tube) output (for which we obtained a patent) that supports the standard, so they too can have one side tied to ground with no worries.
If an output is at risk of damage, this is because its being shorted out, which means it is referencing ground and so does not support the standard. When the circuit references ground, it defeats one of the purposes of using balanced lines, which is to prevent ground loop hum and noise. This practice also allows the interconnect cable to impose an artifact on the the sound, as the shield is being used as a signal circuit return, allowing noise to intermodulate with the signal. Now many studio products that don't support the standard try to get around this problem by having a low output impedance, which swamps the noise, but it should be noted that **any** device that has an XLR output should also have a low output impedance.
