2013/02/06 16:20:09
fireberd
I bought this patch panel, to use for connecting XLR cables to the rear of my recording equipment rack.  The bottom of the patch panel is open (not shielded) and I wonder if that will be an issue?  Or since its balanced XLR the shield isn't needed?
 
I can get a piece of metal and cover the bottom if really needed.
 
 
2013/02/06 18:13:31
The Maillard Reaction
Many XLR connectors are shielded... so there might only be a 1/4" length of the inner wires that isn't shielded where the sheild is trimmed back at the solder terminals.

I know we are taught that a hole in the shield nullifies the effectiveness of the shield, but in practice, the patch bays don't seem problematic... many have very little shielding behind the face plate.

When I asked this very same question, several years ago, about one I use I was advised to try it and see.

It doesn't seem like it's been a problem.





On the other hand, I was working on location today and a coiled AC cable of a light on a dimmer was spraying stuff every where.


Having the back up plan and the sheet metal seems like a good idea.


best regards,
mike





spelling
2013/02/07 06:35:52
fireberd
Mike, thanks.  I talked to my "technical consultant" last evening (a retired broadcast engineer and recording studio design engineer friend) and he confirmed it should not be a problem.





2013/02/07 12:04:37
wst3
just a couple notes...

it is true that any penetration in the shielding will more-or-less make the shielding ineffective.

it is also true that as often as not you don't really need shielding...

Ferrous shields are intended to block electrical fields, they have very little effect on magnetic fields.

Magnetic fields are best defeated with twisted wire and a well designed input circuit.

So if you keep the twist rate uniform, and reasonably tight, between the rear panel and the jacks you should be ok for power line noise. If you have a real RF problem you will need to look at shielding.

All of this is, of course grossly over-simplified, as proper grounding and power distribution plays as important a role.

Bottom line = "it depends"... I hate it when that happens! 
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