XLR Chassis Ground or not

Glaw343

Hi all, I'm going to be making up some cables, mainly for studio and home recording use, but also some live use. should I be connecting pin 1 to the chassis? cheers.

ICBM

It doesn't usually matter, although it won't do any harm. The only difference it will make is if it's plugged into a plastic socket which doesn't have a shell contact, in which case the plug wiring will then be unshielded if it's not connected, but over the length of exposed wire it won't cause significant noise.

Danny1969

I don't as I can see no reason to. It can certainly cause problems if connected to chassis both ends so defo don't do that 

Musicwolf

The question came up in this month's Sound on Sound.  Hugh, as always, came up with the definitive answer.

https://www.soundonsound.com/sound-advice/q-how-should-wire-xlr-cables

Glaw343

Thanks a lot for your replies. so your advice would be to not connect the chassis to pin 1? @Musicwolf thanks fot eh link to the article. it mentioned in there about connecting xlrs together possibly creating an issue, I am pretty unlikely to do that anyway as we generally use a snake so the XLRs don't actually have to be all that long, my main concern would be all of them going into the snake itself as the housing is all metal so perhaps there would be some issue if they all had the ground connected to the shell going into the snake and then to ground on each channel of the desk? for live use I'm generally using SM58's, i checked mine and there is continuity from pin 1 to the inside of the socket so I suppose that would ground one of the connectors anyway, i assume the housing of most mics would work this way? and as @ICBM said there would only really be an issue if the socket is plastic, perhaps the plastic connectors could be on purpose to stop these kinds of issues?. @Danny1969 you mentioned possible problems with it connected both ends what would they be? 

Danny1969

On some bits of kit chassis ground is just that but on other bits of kit it can often be audio ground. This can lead to 2 ground paths and noticeable hum ... you often see rack equipment having to be isolated from the metal rack to cure this issue. There's loads of different scenerios but you will run into the least problems by not connecting pin 1 to the chassis of any cable plug. 

Musicwolf

Danny1969 said:

There's loads of different scenerios but you will run into the least problems by not connecting pin 1 to the chassis of any cable plug. 

I forgot to mention - this is the way that I have always done it.

Glaw343

Danny1969 said:

On some bits of kit chassis ground is just that but on other bits of kit it can often be audio ground. This can lead to 2 ground paths and noticeable hum ... you often see rack equipment having to be isolated from the metal rack to cure this issue. There's loads of different scenerios but you will run into the least problems by not connecting pin 1 to the chassis of any cable plug. 

Thanks a lot for that, I suppose when it comes to safety there isn't any disadvantage to not having the connectors grounded as the equipment is still connected by the shield and phantom is only over the two hot connections so it makes no difference that?

Danny1969

No, safety comes from the equipments earth in the mains cable. Which should always be present. 

Glaw343

Thanks a lot for your help