[SML] XLR mic cables: Pin 1 to case/ground... yes? no?

[Richard Niederberg]

Is there a Lexan, or other non-conductive set screw, available, that could
make the connector mechanically secure, but does not contribute to the 'pin
1' problem?
/s/ Richard

On Thu, Mar 12, 2015 at 6:11 AM, Steve Payne via Stagecraft <
stagecraft at theatrical.net> wrote:

> http://www.rane.com/note151.html
>
> On Wed, Mar 11, 2015 at 3:24 PM, e-mail frank.wood95 via Stagecraft <
> stagecraft at theatrical.net> wrote:
>
>> In my world, there are two different ground connections. One is the
>> safety ground, which comes with the mains supply from the sub-station
>> where it meets the neutral. It is connected to all exposed metalwork.
>>
>> The other is the technical ground, which is usually derived from a
>> substantial ground plate, sometimes buried under the car park. This is
>> used for the cable screens of audio equipment when balanced wiring is
>> used. If the wiring is unbalanced, it may form a part of the signal
>> path, although this is not desirable.
>>
>> It is a firm rule that NEVER the two shall meet. When doing big
>> installations, it was often the custom to connect a battery and buzzer
>> brtween the two, with the incoming technical ground disconnected. If
>> the buzzer went off, the standing instruction to the wiremen was to
>> stop, and to disconnect their work in reverse order until it stopped.
>> Then call an engineer to locate the fault.
>>
>> I remember one TV studio installation where there was a heavy hum
>> signal on the technical ground, over the whole site. Serious experts
>> were called in, who found 7A of ground fault current. By working
>> nights, disconnecting whole areas one at a time, this was traced to
>> the switching and routing centre. Detailed investigation revealed that
>> the switch panels, supplied by an outside contractor, had not used the
>> specified switches, and they all had to be re-made. After that, the
>> problem went away.
>>
>> You can see that this eliminates all the problems at the design and
>> build stages. There was also a policy that cable screens picked up the
>> technical ground from the input of the gear they were connected to.
>> Strictly applied, this eliminates hum loops.
>>
>> On some varieties of XLR connector, the shell securing screw actually
>> drove into pin 1. This is bad news, as the shell inevitably picks up
>> the safety ground from the connector panel, so linking the technical
>> and safety grounds. My advice is to check all your XLR cables for this
>> problem, and to re-terminate those that have the shell connected to
>> pin 1.
>>
>> These general policies were formulated by the BBC, which was learning
>> how to do this job back in the 1920s. They have proved sound ever
>> since.
>>
>> On 11 March 2015 at 02:49, Jon Ares via Stagecraft
>> <stagecraft at theatrical.net> wrote:
>> > On Tue, Mar 10, 2015 at 7:31 PM, tech dept <tech.dept at inbox.com> wrote:
>> >> It sounds like you bought the Beh------ unit. Well, I did and it is
>> holding up well.
>> >
>> > <sheepishly>  I did.  (The Beh----- cable tester, not the POS poopy,
>> > buzzy, fuzzy 4-channel mixer that started this whole mess.)  The cable
>> > tester seems to work fine.... and I like the signal generator function
>> > as well.
>> >
>> > --
>> > Jon Ares
>> > www.arescreative.com
>> > Follow my twits @jon_ares
>> >
>> > ____________________________________________________________
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>>
>>
>>
>> --
>> Frank Wood
>>
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>
>
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-- 
/s/ Richard
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