Balanced to RCA

NEVER short pin3 to pin1 on a balanced XLR output.

This would have been a perfect topic to post in the "pro audio" section.

First let's explain the XLR pins :
1 : ground
2 : hot (+) normal signal
3 : cold (-) inverted signal

A XLR output is always a male XLR and an XLR input is always a female XLR. An easy trick to remember this is just to think of how a microphone looks like : it has a pins -> male XLR and it is a audio source -> output

Although it is not recommended you can make adapter cables from RCA to XLR and vice versa.

The rules are simple :
- RCA ground to XLR ground (pin 1)
- RCA center (non-inverted signal) to XLR hot (pin 2)
- on the MALE XLR cable part ONLY!!! Short cold (pin 3) to ground (pin 1)
The short is to avoid unwanted signals into pin 3. If you leave it floating it can cause unpredictable input (noise). 

Pin 3 on the female XLR of a XLR to RCA cable is left floating otherwise you would short the output and risk damage (you will "overload" the output). Balanced output stages are mostly opamps (some use tranformers) and nearly all of them are protected against shorts, but protections can fail and overloading of the cold(-) signal can negatively influence the hot(+) output signal.

Leaving an output floating is not problem and if you think it is I have one question : do you shorten all the unused RCA outputs on your devices? I guess not.

PS : normally you don't connect XLR chassis to GND (pin 1) but in case you have any hum (ground loop) try connecting those. Some professional devices (especially amplifiers) have a switch for that purpose (ground lift, which factory defaults on "lift").

btw, wasn't it DBX that had an example of those cables in their manual?

@danip,
Though I am not an EE, I think the OP should be aware that not all equipment with balanced interconnects abides by the AEC standard.
Therefore, in an abundance of caution, I suggested using the Jensen Transformers. 
Almarg suggested contacting the manufacturer for a schematic of the wiring just to make sure it abides that standard. If it should, your advice would be sound.
Bob 

NEVER short pin3 to pin1 on a balanced XLR output.

@danip

It’s never a good idea to say "never" :-)

As my previous posts should make clear, I agree with your post when it comes to most designs. But there are exceptions.

You referred to balanced output stages utilizing op amps, and a notable exception to the general guideline of not shorting pin 3 to pin 1 when adapting a balanced output to an unbalanced input applies to op amp-based output stages that are "cross-coupled," which thereby provide outputs that are essentially floating with respect to circuit ground. See pages 11 and 12 of the following reference, in which such circuits are referred to as "active floating sources." And note the statement on page 13 that "Grounding one output line at the driver, which is REQUIRED [emphasis added] to guarantee stability of most "active floating" circuits, degenerates the interface to a completely unbalanced one having no ground noise rejection at all."

https://www.jhbrandt.net/wp-content/uploads/2014/11/Design_of_High-Performance_Balanced_Audio_Interfaces.pdf

That is further confirmed in the Rane document that was referenced earlier in the thread by Rauda1. See diagram 6 on page 7 of that document.

Also, while I’m not specifically familiar with the designs of the output stages of Atma-Sphere’s balanced tube-based preamps, Ralph (Atmasphere) has explicitly stated in past threads here that connecting the balanced outputs of his preamps to unbalanced inputs without grounding pin 3 will result in a huge hum. Which can be expected, given that the balanced outputs of his preamps, although not transformer coupled, are nevertheless floating with respect to circuit ground. And consequently if pin 3 is not grounded the signal on pin 2 will be received by the destination component with an uncontrolled and undefinable voltage relative to pin 1.

There are undoubtedly other such examples.

Regards,
-- Al

What needs to be known when going from an unbalanced/RCA output (such as an active electronic x/o) to a balanced/XLR power amp input (the XLR wired in accordance with AES File 48: Pin 1 ground, Pin 2 non-inverted signal, Pin 3 inverted signal)? Not in terms of impedance considerations, only in regard to the inter-connect RCA/XLR plug wiring connections.