[Amps] The Pin One Problem

[Jim Thomson]

I find it amusing that ALL  consumer gear like stereo’s + TV all have just a 
2 prong 120 vac AC cord on em.    NONE of em use a 3 prong cord, with the grnd. 

As far as using balanced audio cable with a shield, like I use on my balanced audio rack gear,
just about every maker out there will tell you to connect the shield at the sending end only.... even if there
is no pin 1 problem.    IF you reverse it..and connect the shield at the receiving end only,  you will make the RFI a LOT
worse !!     When making up XLR balanced cables, I usually connect the shields at both ends.   But I tried a few with shields 
connected at sending end only and they work juts fine. 

Beware,  the cables I made up have a female xlr, neutrik, at sending end....and a male at rx end.   Since each cable has a 
female –male setup, there is NO way to rvs the cable.   However, IF using  TRS connectors at both ends...like .25 inch  or .21 inch
male plugs on both ends, and one end has the shield opened off, then its very easy  to swap the cable around and have the open shield
at the sending end..... which is a no no for RFI. 

The usual deal these days is to used twisted pair,  shielded cable, with a female xlr on sending end and a male xlr on rx end.
Pin 2+3  are the hot audio leads.  Pin 1 is the grnd.  The neutrik xlr’s all now have a lug on the casing..so u can bond pin 1 to the
case lug..which in turn is bonded  to the chassis.  I wire a  .001 uf @ 25 V  disc ceramic cap between pin 2 + 1.....and a 2nd cap between
pin 3 + 1.   Same deal at other end of cable....so 4 x caps in total for each cable assy. 

later... Jim   VE7RF