[BC] The XLR pinout debate

[Larry Albert]

   This discussion brought to mind a long forgotten "mistake" by a 
non-technical friend.

   Ronnie had a band.  He needed more microphone cables.
He asked about prices for connectors and bulk cable.
Cost of buying 25 male XLR, 25 female XLR, and 500 feet of cable
from broadcast supplier was MUCH less than he would pay at the music store,
his usual source.

  Ronnie could solder reasonably neatly;
he had years of practice repairing broken microphone cables.

  I ordered the connectors and cable for him.
I knew that the connectors and cable were much higher quality
than those he had been buying from the music store.

   Some weeks later he has made up all NEW cables and the band is playing a 
job.

   Lots of HUM in everything.

   I was in the audience and watched him try several thing which didn't 
reduce the HUM.

   I walked up to see IF I could be of any help.

   He quickly said "That NEW cable is you sold me is bad, just listen to them."

   I unplugged all but one cable - HUM!!

   Borrowed a store-bought cable from the guitar player - NO hum ??

   Asked Ronnie if he had connected the shields at both ends.  Yes.

   I said something about it being easy to mis-wire a cable and have the 
shield contacting the shell at microphone end.
   I don't remember exactly what I said about the wiring being backwards 
from one end to the other.
   Shield to left on connector at one end an to the right at connector on 
the other end.

   " @#$%^&"   He started grabbing his old cables off of his trailer and 
finally got the music going.

   Ronnie had opened one store-bought cable for a wiring 
example.  Unfortunately he only opened one end of the cable.

   He had wired every shield to the leftmost pin of the connector.

   The next week he checked and fixed every one of his cables.

   He also bought a fancy cable tester from his music store as the cost of 
his education.



Albert






At 04:08 PM 8/13/06 +1000, you wrote:

>>< SNIP >
>
>In a perfect world, yes. Here's my real-world experience.
>Station A is wired "pin 2 hot", station B is wired "pin 3 hot" - Station A 
>owner buys station B, and starts sharing resources like OB gear. Now we 
>have a jumble of XLR leads with the "traditional" hot wire (red, white, 
>whatever) wired to different pins.
>Eventually the two stations are bought under the one roof (a "pin 2 hot" 
>plant naturally).
>After a couple of bouts of phase "strangeness" on stereo circuits caused 
>by legacy XLR cables miswired I did a stocktake - after investing in a 
>cable wiremap tester.
>I found a worryingly large number of pin 2<->3 transposed cables in the 
>spare & OB cable stockpile.
>My take on the reason - careless or clueless techs repairing the cables 
>over the years since the acquisition, dealing with only one end, and 
>wiring it to their idea of what's right. Some of these cables found their 
>way into the combined station studio rebuild as one side of a stereo pair.
>They would have gone largely unnoticed in a typical OB lash-up, and if 
>they did cause a problem it could have been blamed on some other factor at 
>the OB.
>Now whenever I have to open up one of the pin-3-hot leads, and resolder 
>one end, I take the time to rewire both ends to the standard.

< SNIP >



>Cheers!
>
>--
>=============================
>Peter Smerdon.
>
>Radio 3mp - Easy Listening
>sen-1116  - Let's Talk Sport
>
>Melbourne, Australia.
>=============================