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Phantom power weirdness.
Old 22nd October 2019
  #1
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Phantom power weirdness.

Been touring with a brand new condenser microphone and XLR cable which has worked great for most of the summer except for two gigs. On both occasions the microphone did not operate because of a lack of phantom power, changed cables etc still wouldn't work, plugged in a Shure KSM 9 using the same cable and channel and it worked.

Took the mic home and plugged it into my gear and it worked like a charm, couldn't get it to misbehave at all, even tried it in several preamps, console channels, interface and checked it with my Fluke etc and there were no problems. Took it back out on the road, several festivals all over the place and it worked, until this weekend when the same problem showed up again, went through the same ritual as before and it worked with another Shure condenser mic which worked.

Fortunately I had some time to go a little further and plugged it directly into the back of the console and it worked...plugged it directly into the Midas stage-box and it worked. so the problem was clearly with the sub-snake, but what I can't understand is why the problem only shows up with my microphone.
Old 23rd October 2019
  #2
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hm... - did you get to plug the mic into different channels on those occasions when it didn't work?

i've had issues with old and cheap multicores which used a common shield for all channels and in the olden days with some analog desks not providing enough phantom power to drive lots of power-hungry neumann mics - but this...?
Old 23rd October 2019
  #3
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Quote:
Originally Posted by deedeeyeah View Post
hm... - did you get to plug the mic into different channels on those occasions when it didn't work?

i've had issues with old and cheap multicores which used a common shield for all channels and in the olden days with some analog desks not providing enough phantom power to drive lots of power-hungry neumann mics - but this...?
I was only able to do that on this last occasion and plugging it directly into the console worked on every channel, the same with the stage box. It works perfectly with all the outboard preamps I have at home.

In both situations these were very modern, new systems staffed with competent crew who were just as puzzled as I.
Old 23rd October 2019
  #4
Gear Maniac
 

You could carry a multimeter and check the voltage at the desks it doesn't work on, then also see if there is voltage drop at the snake, then last at the end of the mic cable. I've had condensers that need a full 48v and won't work at 40v
Old 23rd October 2019
  #5
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Quote:
Originally Posted by DownTheLine View Post
You could carry a multimeter and check the voltage at the desks it doesn't work on, then also see if there is voltage drop at the snake, then last at the end of the mic cable. I've had condensers that need a full 48v and won't work at 40v
I suspected that this was clearly a power problem but just can’t figure out what exactly is going on. If I get the chance in the future I’ll check this, in any case I know that the mic does not have a problem and will work if I plug it directly into the stage box or console.
Old 23rd October 2019
  #6
Lots of stage boxes are full of corroded XLRs from being "on stage" and "in the weather". I use to carry a can of Caig DeOxit https://caig.com/deoxit-d-series/ and use it before I plugged in my mics. It does not take much corrosion to make a ground connection high resistance and therefor the phantom cannot work properly. FWIW.
Old 24th October 2019
  #7
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audiospecific's Avatar
 

Quote:
Originally Posted by Samc View Post
Been touring with a brand new condenser microphone and XLR cable which has worked great for most of the summer except for two gigs. On both occasions the microphone did not operate because of a lack of phantom power, changed cables etc still wouldn't work, plugged in a Shure KSM 9 using the same cable and channel and it worked.

Took the mic home and plugged it into my gear and it worked like a charm, couldn't get it to misbehave at all, even tried it in several preamps, console channels, interface and checked it with my Fluke etc and there were no problems. Took it back out on the road, several festivals all over the place and it worked, until this weekend when the same problem showed up again, went through the same ritual as before and it worked with another Shure condenser mic which worked.

Fortunately I had some time to go a little further and plugged it directly into the back of the console and it worked...plugged it directly into the Midas stage-box and it worked. so the problem was clearly with the sub-snake, but what I can't understand is why the problem only shows up with my microphone.
In certain situations, it's better to use a phantom power brick, because the current demand on a long cord run can cause poor performance or functionality. Usually, its the norm to have the monitor desk provide the phantom power on the classic analog live rig, and now these days with digital i/o, the stage boxes provide the phantom.
Old 24th October 2019
  #8
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Quote:
Originally Posted by DownTheLine View Post
You could carry a multimeter and check the voltage at the desks it doesn't work on, then also see if there is voltage drop at the snake, then last at the end of the mic cable. I've had condensers that need a full 48v and won't work at 40v
Quote:
Originally Posted by Thomas W. Bethe View Post
Lots of stage boxes are full of corroded XLRs from being "on stage" and "in the weather". I use to carry a can of Caig DeOxit https://caig.com/deoxit-d-series/ and use it before I plugged in my mics. It does not take much corrosion to make a ground connection high resistance and therefor the phantom cannot work properly. FWIW.
Quote:
Originally Posted by audiospecific View Post
In certain situations, it's better to use a phantom power brick, because the current demand on a long cord run can cause poor performance or functionality. Usually, its the norm to have the monitor desk provide the phantom power on the classic analog live rig, and now these days with digital i/o, the stage boxes provide the phantom.
At this stage it's probably a lot easier for me to just add a line in the rider about having 48v for my condensers or carry an extra dynamic to use when this problem shows up in the future...almost every future gig for the rest of the year is a fly date, carrying more stuff is practically not doable at this point.
Old 24th October 2019
  #9
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Have you opened up the mic to look for cold solder connects on the PCB inside? Or wired connections to PCB?
Old 24th October 2019
  #10
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Quote:
Originally Posted by Pro Sound Guy View Post
Have you opened up the mic to look for cold solder connects on the PCB inside? Or wired connections to PCB?
No, I don't see the point in doing that...the mic works without any problems in every other situation, including when plugged directly into the stage-box and console. I have not been able to get the mic to behave badly in any other situation.
Old 24th October 2019
  #11
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Just an off-the-wall guess: maybe the intermittent mic has ever so slightly smaller XLR pins than the Shure, just enough different to fail to make reliable contact with a loose/worn mating connector? Though I would have thought that would lead to a lot of obvious handling noise as well.

As I suspect we all know, intermittent problems are most often the result of some bad connector or connection in a cable or device. That doesn't appear to be the explanation here, at least at first glance, which leaves me as befuddled as anyone.
Old 24th October 2019
  #12
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Quote:
Originally Posted by DrewE View Post
Just an off-the-wall guess: maybe the intermittent mic has ever so slightly smaller XLR pins than the Shure, just enough different to fail to make reliable contact with a loose/worn mating connector? Though I would have thought that would lead to a lot of obvious handling noise as well.

As I suspect we all know, intermittent problems are most often the result of some bad connector or connection in a cable or device. That doesn't appear to be the explanation here, at least at first glance, which leaves me as befuddled as anyone.
I doubt this is the problem, but I am going to measure the pins with a caliper in a few minutes.

The problem is not really intermittent, the mic just didn't work in two very particular situations and I'm more inclined to believe that the problem lies with low voltage due to the very long cable runs and the complexity of the installations in question.
Old 24th October 2019
  #13
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So I measured the pins with my caliper and the pins are the standard diameter size....no rust or other type of corrosion etc, and I could not recreate the problem no matter how hard I tried.
Old 24th October 2019
  #14
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Quote:
Originally Posted by Samc View Post
(...) The problem is not really intermittent, the mic just didn't work in two very particular situations and I'm more inclined to believe that the problem lies with low voltage due to the very long cable runs and the complexity of the installations in question.
when running a signal down a very long line, level and voltage don't drastically drop but gradually get lower at larger distance.

i can't imagine that a power hungry mic shuts down when being slightly underpowered: afaik most neumann mics need 48v; they start sounding strange when getting less but i never experienced one to stop working because of that.

what you experienced imo indicates that a cable was not correctly wired - time consuming/hard to track down in large installations...
Old 24th October 2019
  #15
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Quote:
Originally Posted by deedeeyeah View Post
when running a signal down a very long line, level and voltage don't drastically drop but gradually get lower at larger distance.

i can't imagine that a power hungry mic shuts down when being slightly underpowered: afaik most neumann mics need 48v; they start sounding strange when getting less but i never experienced one to stop working because of that.

what you experienced imo indicates that a cable was not correctly wired - time consuming/hard to track down in large installations...
I hear you, but I have never seen this before either, and I can't wrap my brain around it...the frustration is not being able to recreate the problem.

Last edited by Samc; 25th October 2019 at 12:22 AM..
Old 24th October 2019
  #16
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I had an Audix Vx10 condensor vocal mic. I dumped it cause it required a full 48 volts phantom to work. Small mixers and my rack mount Soundcraft UI24r would not
power it up.
If I was running large consoles with robust power supplies I guess I would have had no problem with it.
If for any reason you lift pin 1 you will not have phantom.
Old 25th October 2019
  #17
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Considering that phantom power is supplied via two 6.8 kOhm resistors, even a kilometer of mic cable (which usually has a resistance of about 100 Ohms) shouldn't significantly change the voltage at the end.

It is quite possible that some mics would still somewhat work with pin 3 disconnected or shorted to ground while many won't.
Old 4 weeks ago
  #18
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Update: after several weeks of continued gigs with the mic, I have not had or been able to recreate the problem, I and others have done several tests on the mic but have been unable to come up with a solid reason for what happened. After everything that I’ve put it through, I am convinced that nothing is wrong with the microphone, but is unable to understand why the Shure microphone worked when this one didn’t...will keep checking.
Old 4 weeks ago
  #19
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If it works don't fix it.
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