[SML] Testing integrity of mic cables....

[e-mail frank.wood95]

Some makes of XLR automatically connect pin 1 to the connector shell,
via the shell-insert fixing screw, which penetrates pin 1. Unless the
earthing arrangements have been carefully thought out, thican cause a
lot of trouble, by greating earth loops and so on.

You need to design the earth connections as carefully as the rest of
the system. This is why transformer balance ia best for inputs, and
desirable throughout. It is expensive in first cost, and you can often
get away with a pseudo-balanced output, using two op-amps, which is a
much cheaper way. But when you figure in the cost of the time spent in
disentangling the problems, it may be charper in the long run.


On 27 February 2015 at 23:24, Dan Sheehan via Stagecraft
<stagecraft at theatrical.net> wrote:
> possible that cable checks out OK on the continuity test,
> but connector fails to make good contact to the equipment,
> seen this with old and/or cheap connectors (females get sloppy).
>
> also, Pin 1 should be cable shield  (or signal ground)  and should
> *not* connect to connector shell,
> continuity tester might not check for this and if there is a spurious
> shell connection (=equipment chassis)
> that could lead to a hum or buzz
> --
> ...Dan Sheehan
> Fixer of things that break
>
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-- 
Frank Wood