As far as I understand it, it is the twist in the two signal cores that if
interference is induced this is then cancelled out when connected to the
preamps input transformer. That is why the two signals cores are not single
cores but double cores and twisted together in the way they are. Hence the term
quad as there are four cores which carry the signal, live and return
Grounding one of the signal pairs would not be a good idea at all and would
impair the rejection properties of the star quad.
Canare used to make a BBC specification star quad which has stood the test of
time, I don't know if they still do but it was very good and not overly
expensive.
http://www.canford.co.uk/ProductResources/ig/4160.pdf
Sent from my iPad
On 23 Jun 2012, at 07:30, Mike Feldman <> wrote:
> On 22 Jun, 2012, at 7:06 PM, Avocet wrote:
>
> > > Are you saying only one blue wire would go to pin 3, and the other
> > > blue wire to the ground? And one white to pin 2, the other to
> > > ground?
> >
> > Vicki,
> >
> > That's the BBC way I was taught for wiring quad cable. Perhaps the
> > other way also balances out strong magnetic fields but I've never had
> > one of those to test out. :-)
>
> I've always paired like colors, per Canare. Seems to me that grounding
> one each of blue and white would be like adding small capacitors to
> ground,
> which would kill some of the high frequencies with the roll-off point
> set
> by how long the cable is. Of course, that may be exactly what the BBC
> engineers wanted if the roll-off is above the audio frequencies of
> interest
> and you want to block RF. But I understood that the geometry of star-
> quad
> windings is such that magnetically induced currents along the length
> cancel.
>
> -- Mike
>
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