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For my server I will use a Raspberry Pi 3/4 as KVM. Instead of pulling the current for the Raspberry from the PSU's +5 VSB, I will use the (new) USB-C power supply of Raspberry. It has wires with a gauge of 18 AWG.

However, the Raspberry will reside within the case. Therefore, I want to solder an XLR male connector onto the Raspberry power supply cable (so XLR instead of USB-C or Micro-USB) and to the server case I will assemble an XLR female socket. The XLR male jack (Neutrik NC3MXX) is suitable for cable diameters from 3.5 to 8.0 mm and as the power supply cable is round and 3.5 mm thick, this will work perfectly.

I will then connect the two soldered cables of the XLR female socket to this cool adapter:

enter image description here

As to my other question about the Ethernet port grounding, I have the same question here:

The server case is grounded, thus the XRL female socket will be too. Do I need to make sure that the Raspberry power supply ground connected to the XRL female socket has no connection to ground (due to the metal chassis of the socket) of the PSU? As with XLR connections sometimes - not always - pin 1 is not only connected to the shield of the XLR cable, but also to ground (earth), I think it would be consequential to only use pin 2 (+) and pin 3 (-) and leave pin 1 unconnected.

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    \$\begingroup\$ Why XLR of all the connectors in the world? Why not use a simple DC barrel connector, or USB for example? \$\endgroup\$
    – TooTea
    Feb 6 at 15:38
  • \$\begingroup\$ Reason is the following: Neutrik has XRL, RJ45 and USB-A jacks, but no Micro-USB or USB-C jacks while the Raspberry Pi power supply only has USB-C and Micro-USB for 5 V. The one for DC is 8 V. RPI 3 has Micro-USB, RPI 4 has USB-C. Due to the bad availability I may have to use both V3 and V4, as I have multiple servers. That is really all a mess. Because it is so simple and robust to solder XLR connectors, I think that is the most safe, simple and consistent way, also the XLR female jack can be assembled to the chassis easily, with all the DC jacks I was looking for that would not be so easy. \$\endgroup\$
    – Tintenfisch
    Feb 6 at 15:51

1 Answer 1

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Pin 1 on XLR connector is just a pin. It is not connected to connector metal chassis, just like pins 2 and 3 are not. Unless you connect it yourself. Sometimes 3 pin XLR connectors have a 4th pin for the shell.

So if you assume pin 1 is ground or shield or whatever, it is for 3-pin audio cables, and 3-pin DMX cables, but the connector metal shell on cable is not connected anywhere in the cable for safety reasons. The metal shell is grounded to case just because you plug it in to a socket which has the metal chassis connected to devuce grounded metal chassis.

On a side note, it may not be a great idea to use a 3-pin XLR for power. Someone will connect it to something which blows up. And the metal pins are exposed so you can also easily short the power supply if you put that plug on a supply.

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  • \$\begingroup\$ Why do you think there is a risk using XLR? With DC (coaxial power connectors) it would be the same and as they are more widely used, the probability of connecting such a power supply to a wrong device would be the same if not higher. With standardized plugs there is always a risk to use power supplies with either too high voltage or too low amperage. You are right that the metal pins of the power supply are exposed, but they are hidden within the metal jack chassis. How do you think they could short the power supply? \$\endgroup\$
    – Tintenfisch
    Feb 6 at 16:04
  • \$\begingroup\$ The 3-pin XLR is used everywhere. It is already used in many applicationa where it shouldn't, even for power supplies and cheapest possible fog machines may have live mains on it. Plug any incompatible equipment together and they might be toast. At least use a 4-pin XLR which is more typically used for power. And the reason whe the part with metal prongs is used on the device side instead of supply side is the short circuits. If you have small metal objects in your environment, like computer screws, there is a risk of short, and when using the prongs on device side, there isn't. \$\endgroup\$
    – Justme
    Feb 6 at 17:15
  • \$\begingroup\$ Thanks a lot for your answer! And yes, now I totally agree with you - I had an error in logic. Even if one would not see much risk shorting the power supply, it is way more unlikely to short the power supply when having a female instead of male connector on it. There is absolutely no reason to use a male connector on the power supply. \$\endgroup\$
    – Tintenfisch
    Feb 6 at 17:33
  • \$\begingroup\$ Currently I am thinking about this. Also very easy to assemble. What do you think about it? \$\endgroup\$
    – Tintenfisch
    Feb 7 at 17:33

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