Connecting XLR shields

Archived from groups: rec.audio.tech (More info?)

Hi!

Just out of curiosity - does anyone know why XLR cables almost never
have the shield connected? How would it afftect things if it were
connected?

Harry

Archived from groups: rec.audio.tech (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:113rlms1n5omc94@corp.supernews.com...
> "Harry Houdini" wrote ...
>> Just out of curiosity - does anyone know why XLR cables almost never have
>> the shield connected? How would it afftect things if it were connected?
>
> Presumably you mean the connector shell and not the cable
> shield (screen)? Seems highly doubtful that you could get
> away with leaving the shield floating.
>
> OTOH, making a connection to the shell (at either end)
> appears to be nowhere near as critical. I suspect that people who operate
> in high RF areas can't be as casual about that as the rest of us.

Not casual - deliberate. If you are going through a stage ar wall box, with
multiple connectors, you will instantly have lots of potential ground loops
which are very susceptible to rf interference. Even just a single cable
connected to a grounded metal wall box will likely cause problems.


geoff

Archived from groups: rec.audio.tech (More info?)

As I re-call connecting the shield to the shell creates a ground loop
finder.
Handy if you need ground loops.

Harry Houdini wrote:

> Hi!
>
> Just out of curiosity - does anyone know why XLR cables almost never
> have the shield connected? How would it afftect things if it were
> connected?
>
> Harry

--
Hope this helps

Bill Mayhew
Mayhew & Company, Rental, Sales, Service
<http://www.mayhewco.com>

Archived from groups: rec.audio.tech (More info?)

Richard,

Thank you so much for your response.

Yes, I did mean the shell.


On Sun, 20 Mar 2005 12:02:35 -0800, "Richard Crowley"
<rcrowley7@xprt.net> wrote:

>"Harry Houdini" wrote ...
>> Just out of curiosity - does anyone know why XLR cables almost
>> never have the shield connected? How would it afftect things if it
>> were connected?
>
>Presumably you mean the connector shell and not the cable
>shield (screen)? Seems highly doubtful that you could get
>away with leaving the shield floating.
>
>OTOH, making a connection to the shell (at either end)
>appears to be nowhere near as critical. I suspect that people
>who operate in high RF areas can't be as casual about that as
>the rest of us.

Archived from groups: rec.audio.tech (More info?)

Jim,

Thank you for your thoughtful and generous response.

Questions: So if I understand you correctly, I should ground the panel
chassis and then solder the XLR interconnect shells to the chassis?
Then, I should solder the shells of any XLR cables going into/out of
the panels to pin 1. Right?

Can I connect the chassis plates to the ground on a nearby AC line or
do I have to run a separate line?

Can I connect both junction faces to the same ground?

Kind regards,

Harry

On Sun, 20 Mar 2005 21:08:18 GMT, "Jim Gregory"
<jim.greg@ntlworld.com> wrote:

>The shell of any panel-mounted *metal* flange XLR connector, say on a
>facilities panel or wallbox, is usually grounded by its corner or radial
>screws to the metalwork, assuming that the panel *is* already grounded - for
>Safety reasons. When a flying lead *metal* case XLR connector (male or
>female, 3 -pole or more) is inserted there, its shell gets automatically
>grounded. Therefore it should not be linked to pin 1 which would get
>grounded twice!.
>If using lightweight *plastic* XLRs, Caution - there is not always a 4th
>pole embedded in the connector.
>XLR pin 1 is supposed to be longer than the other two - and so mates first
>and breaks last, allegedly.
>But the *shell connection tag* of the wandering end metal-cased 3-pole
>female XLR cable socket should be linked to pin 1 to make the microphone (or
>whatever source) safe and immune from RF.
>I always connected studio mic cables' and mic extenders' XLR females from
>pin 1 to shell.
>Even if the signal-pair part of the cable in a technical area is
>interruptible by normalling jacks and patching, the screen should be
>continuous to ground.
>No matter what series length and how many add-on extenders are used, pin 1
>should be traceable to the active electronics chassis elsewhere, which good
>practice dictates is always at robust ground potential.
>I believe the same philosophy does not always go for *shell connection tag*
>of studio/gig wander ends with metal-cased 3-pole MALE XLR plugs used for
>taking feeds, foldback, etc.
>ANOMALY... If o/p cable metal connector shells are always linked to their
>pin1, should the metalwork for an i/p cable accidentally touch the metalwork
>for an o/p cable on stage or in a studio, there could be a subtle ground
>loop.
>