Is this cable incorrectly wired?

[miiaow]

I’ve seen this cable referenced and recommended several placed and have come across some conflicting information regarding its wiring. First, let me describe the application I have in mind:

pre-amp RCA out --- RCA to XLR cables --- pwr amp XLR input

The cables from monoprice:

https://www.monoprice.com/product?p_id=4777

The wiring diagram from monoprice:

According to this diagram, the ground on the XLR connector is connected to the shield and then also connected to the ring on the RCA connector. This conflicts with Rane note 110’s wiring diagram for an RCA to XLR cable:

(Source: https://www.rane.com/note110.html)

As you can see, the difference between the two diagrams is that in the Rane note diagram, the shield is not connected to the ring on the RCA connector.

Someone also made the following comment in the Q&A section on the monoprice product page:

Q: It's this a balanced cable?
A: No. RCA is Unbalanced,
However, 1 side of the link is 'balanced' which means the sheath goes to ground.
the RCA does not have a ground to go to. So that makes that side Unbalanced.
This cable is however still incorrectly wired, as it connects the sheath to the ring on the RCA side, and you should NOT have that connected. I modify these to be correctly wired.

Can anybody help clear this up?

 

[Killingbeans]

As far as I can tell, the cable assemblies on the Rane page are designed as a last desperate solution for those who are plagued by ground loops in poorly designed gear.

The Monoprice diagram is the correct solution for normal gear with proper grounding.

 

[solderdude]

so the top one is correct

 

[Wayne A. Pflughaupt]

Either will pass a signal, as the signal (-) and chassis share continuity with most unbalanced gear. If you get hum, then lift the ground. I've never had any issues connecting the two in my system.

Regards,
Wayne A. Pflughaupt

 

[Wombat]

FYI. Rane: Grounding And Shielding Audio Devices

 

[raindance]

Lifting the shield in an unbalanced situation will do nothing for ground loops, FYI, it is supposed to be the signal return path. Of course, there are cable companies that will tell you otherwise, but, unless they are able to train electrons to do things outside the laws of physics, it won't make any difference.

Also note that shorting of pins 1 and 3 should only be done on an XLR INPUT, never on an output (as it would short half the output stage and possibly destroy it).

In a true balanced system, signal is carried by the two conductors and the shield is purely a shield, not a signal return, so it can be dropped at one end.

 

[DonH56]

Shorting the (-) signal input of the XLR is common. Rarely it can cause problems at the receiver by unbiasing the input stage but most all gear is designed to handle that situation. Using a resistor that roughly matches the input impedance of the receiver (amp) will provide better common-mode rejection but also increase noise.

What Rane shows is more typical -- that scheme allows the shield to act more like it should to reject noise to the signal pair. In practice, for consumer electronics, it rarely makes a difference IME. And as @raindance said it won't help break a ground loop. Again, if I have the option, I'd try sticking a series resistor on the (-) line to see if it makes things better or worse. That will generally break a ground loop but may add wideband noise so hard to say which will be best.