Topic: Mic Cables - what happens when pin 1 & pin 3 are shorted ??

[JasonSobel]

What happens when pin 1 & pin 3 are shorted?

So I made a set of mic cables.  The regular XLR connectors are fairly easy, but the mini-XLR for audix mics proved to be a bit of a challenge.  it was tight, but I thought I had it done good.  afterwards, I checked for continuity for 1>1, 2>2, and 3>3.  and I also checked for continuity from 1>2, 1>3, and 2>3 to make sure that those were NOT connected.  the cables checked out fine, and all was good.  I recorded a few shows with no problems, and the recordings came out great

Fast forward to Sunday night (my last taping experience with the Audix mics, my MG's should be here today or tomorrow).  The entire night, the right channel is doing something funny.  I was running on-stage, and the mic position was sort of funny.  Hard to describe, so I won't get into it right now.  but because of that, I wasn't sure if the level discrepency between channels was because of an equipment problem, or just because of the funny mic placement.  I listen and transfer the short second set, and there was static and distortion all through the right channel.  almost what I'd expect if the mic capsule wasn't getting a full 48 volts.  so that immediately rules out the funny mic placement as being the culprit.  I then check the right cable for continuity.  1>1 = check, 2>2 = check, 3>3 = check, 1>3 = WTF?  So now, pins 1 & 3 are shorted together.  That's obviously the problem.  My immediate thoughts were "shit, did I fry the mic?" and then "shit, did I fry my V3?"  I then spent some time testing everything out at home, with the good, original cable that I still have (the one that came with the mics, not one that I soldered).  I tested both mics with both channels of the V3, and everything appears to be normal.

So, I know what didn't happen.  The mics didn't get fried, the V3 didn't get fried.  and I know a non-technical thing that did happen, my recording is basically useless (luckily Rob was taping as well, so my source wasn't the only one).  but I'd like to understand what happened on a more technical level.

From the online V3 manual, Pin 1 = ground, pin 2 = positive, and pin 3 = negative.  Phantom power runs on pin 2 & pin 3.

What are possible consequences of shorted connections?  Did I luck out that it was pin 1 & pin 3?  if it was pins 2 & 3, would I have been screwed?  it seems to me that shorting pin 2 & pin 3 could have been a lot worse??  I'd be happy to post a picture of the waveform (in Cool Edit) if anyone is interested.  Also, I could host a short .mp3 sample if anyone is curious what it sounds like.

Any input is greatly appreciated.

and finally, the moral of the story.  My soldering skills just don't cut it for a 3-pin connector the size of the mini-XLR.  I'm comfortable with a standard XLR connector, but that's probably the limit of my soldering skills at this point

thanks,
Jason

[Lil Kim Jong-Il]

A well designed DC power supply will not source current when it's terminals are shorted.  I would expect the V3 to have a well designed phantom supply so that no damage occurs if +48 is on when the signal pins are shorted or the hot pin is shorted to ground. 

If you don't trust your soldering, you can use teflon plumbers tape to wrap as insulation around the joint so that if it fails it will not move to another pin and cause a short.