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Author Topic: X32 + S16 popping with shielded cat5e cable and ethercon connectors  (Read 1280 times)

Mark van Leeuwen

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #20 on: September 06, 2017, 10:34:25 pm »

Check to see if the camera has phantom power applied to the 3.5mm input.  Phantom will charge up any output coupling capacitors; when they reach discharge voltage they'll put a DC spike in the signal (and to the ground plane of the console).

You might do a search for the work Dan Mortensen and another engineer did with a BBQ lighter... remove the protective tip to expose the piezo element on a fuel-free lighter.  Spark up any exposed metal on the mixer or S16 and see what happens.  If this doesn't induce a drop out, the problem is not the CAT STP cable or its terminations...

My experience with UTP was that the pop was not like gunshot (it wasn't alarmingly loud, just irritating).  That level makes me think of a phantom power issue somewhere on the input side.

Thanks for the suggestions.

The camera is on XLR out so there is no phantom power on that cable. But I will try removing all phantom power inputs. The popping and dropouts have only occurred when the room is full of people and the weather is dry, which means my opportunities to test changes are somewhat limited. Thankfully the church congregation has been patient with me chasing down the problem and have put up with me disabling parts of the system.

I have seen the Youtube videos uploaded by Brian Wynne. I was rather pleased to find someone else had experienced the problem and was able to recreate it. I had wondered about zapping our X32 and S16 the same way, but feel reluctant to put the church's gear at risk!
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Tim McCulloch

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #21 on: September 07, 2017, 11:55:51 am »

Thanks for the suggestions.

The camera is on XLR out so there is no phantom power on that cable. But I will try removing all phantom power inputs. The popping and dropouts have only occurred when the room is full of people and the weather is dry, which means my opportunities to test changes are somewhat limited. Thankfully the church congregation has been patient with me chasing down the problem and have put up with me disabling parts of the system.

I have seen the Youtube videos uploaded by Brian Wynne. I was rather pleased to find someone else had experienced the problem and was able to recreate it. I had wondered about zapping our X32 and S16 the same way, but feel reluctant to put the church's gear at risk!

Brian is the other engineer I was thinking of (but couldn't remember his name).

You won't damage the church's mixer or S16 - look at how many times Brian and Dan tested their respective consoles without damage.

ESD is getting into the system somehow and I think it's prudent to start with known failure modes and eliminate or confirm them.  You can't test for what you don't know....
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Mike Sokol

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #22 on: September 12, 2017, 08:03:42 am »

Yes, a few channels do use phantom power. I have tried moving/jiggling all connections but could not reproduce it. Also, the popping is much louder than I would expect from a bad connection, it is like a gunshot, so that is why I have been suspecting it must be an ESD.

A phantom power XLR cable with an intermittent connection can sound like a gunshot. I once had a bass guitar active (phantom powered) DI that acted like that. One of the XLR wires inside the case was broken and would make/break contact if you tapped on the DI box. It would produce a pulse at full PA power, which was pretty scary and could have taken out some drivers if it kept happening.

Rob Spence

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #23 on: September 12, 2017, 03:40:09 pm »

Thanks for the suggestions.

The camera is on XLR out so there is no phantom power on that cable. But I will try removing all phantom power inputs. The popping and dropouts have only occurred when the room is full of people and the weather is dry, which means my opportunities to test changes are somewhat limited. Thankfully the church congregation has been patient with me chasing down the problem and have put up with me disabling parts of the system.

I have seen the Youtube videos uploaded by Brian Wynne. I was rather pleased to find someone else had experienced the problem and was able to recreate it. I had wondered about zapping our X32 and S16 the same way, but feel reluctant to put the church's gear at risk!

Cameras often have phantom on THEIR input because they often use condenser mics.

That is what Tim is concerned about.

I always put an isolation transformer between my output and someone else's input.

Some mixers can be damaged by getting phantom applied to their outputs.



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Mark van Leeuwen

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #24 on: September 13, 2017, 09:47:09 am »

A phantom power XLR cable with an intermittent connection can sound like a gunshot. I once had a bass guitar active (phantom powered) DI that acted like that. One of the XLR wires inside the case was broken and would make/break contact if you tapped on the DI box. It would produce a pulse at full PA power, which was pretty scary and could have taken out some drivers if it kept happening.

Thanks for sharing that experience. Following suggestions made by others, I disconnected all inputs with phantom power last Sunday. There were three drop-outs during the service where all sound was lost for less than a second - no loud popping this time. I believe it is random whether we have a loud pop or drop-out. We've  had both before. At this stage, I think the symptoms still point to ESD being the cause.

Cameras often have phantom on THEIR input because they often use condenser mics.

That is what Tim is concerned about.

I always put an isolation transformer between my output and someone else's input.

Some mixers can be damaged by getting phantom applied to their outputs.

Thanks for the clarification. Based on recommendations here, I bought an isolation transformer and have inserted that into the two outs that go to the camera and splitter.

If that makes no difference, then I plan to use the BBQ lighter test to see if I can recreate the problem.
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Mark van Leeuwen

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Re: X32 + S16 popping with shielded cat5e cable and ethercon connectors
« Reply #25 on: September 25, 2017, 09:42:39 am »

Unfortunately, I still have not solved the problem.

I have inserted an isolation transformer in the two outputs. I made another CAT5e cable and following advice I read elsewhere folded the foil shield over the outside of the cable with the drain wire running under and over it then several times wrapped tightly around the RJ45 metal strain relief. This is in addition to earlier changes where I disconnected the speaker outputs and all phantom powered inputs.

The only connections that remain to the S16 are 2 dynamic mics and the 2 outputs protected with the isolation transformer.

Despite all that, we still had a few loud pops and drop-outs captured on both the X32 USB recording and the video stream.

I have now adapted a gas lighter and zapped the system in various places hundreds of times: S16, X32 core, XLR cable ends.

I managed to produce one pop and that was by zapping the ethercon connector on the CAT5e cable plugged into the S16 AES50 A port. Can anyone explain how that could happen?

I made one other test: I disconnected the CAT5e from the X32 and tested continuity by putting an ammeter between the disconnected ethercon and the X32 chassis. That proved continuity over the the CAT5e cable shielding to the S16 chassis, through the building wiring back the X32. I conclude from that test that the CAT5e shielding is grounded.

Any further suggestions would be appreciated.
« Last Edit: September 25, 2017, 10:42:04 pm by Mark van Leeuwen »
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