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Author Topic: Help Troubleshooting Setup with Floor Boxes; Splitters  (Read 361 times)

Sam Blount

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Help Troubleshooting Setup with Floor Boxes; Splitters
« on: February 01, 2018, 07:46:21 pm »

Hi all,

Having an issue with a setup including multiple floor boxes, splitters, and phantom powered mics. The splitters send to automatic mixers for reinforcement and a mixer for recorded audio. We have a separate room where the rack is.

Over the past year I've been getting buzzing on some of my channels and it seems to be spreading. I had the installation company out multiple times and they troubleshot the system, but couldn't find out what the problem is. Ground lift doesn't do anything, xlr's are fine, mics are fine, etc. They suggested rerunning all the cable from the floor boxes but wouldn't guarantee that would fix the problem.

In the mean time, I had a quote done on a wireless Shure Microflex System, that would take the floor boxes out of play. I also ordered some Shure MX418DS gooseneck mics for another room. I currently have Sennheiser MZTX31 goose necks.

I decided to put one of the new Shure mics in through one of the good floor box inputs and I get buzzing through the speakers(I tested some of the other new mics and they all buzz). I checked all the other inputs and two weren't buzzing, but all the others were. The older Sennheisers do not buzz in the good inputs. Another point to add is I had the same Shure mic in line a couple years ago as a test mic, and I had no problems.

The splitters provide the phantom power, is it possible that the buzzing is due to the splitters not providing the correct amount of power to the mics? They are over a grand a piece, so it would hurt to replace them and it doesn't fix the problem.

Has anyone had issues with older floor boxes? I took the panels off and all connections look secure.

Any help would be much appreciated!

Edit: Also like to add that the bad channels can pop, I'll see a spike on my mixer.
« Last Edit: February 01, 2018, 07:52:12 pm by Sam Blount »
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Mike Caldwell

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #1 on: February 01, 2018, 09:33:50 pm »

Floor boxes themselves will not cause hum or buzz unless....pin 1 on the xlr connectors is tied to the shell/outer body of the XLR connector and then that could be problem even more so if the floor box is tied to the building grounding with a piece of conduit. Do you have any 1/4 inch jacks mounted in the floor box that are not insulated from the box.

Do you get buzz on the system from any of the floor box mic channels with nothing plugged into those channels?

If you disconnect the lines feeding the recording mixer does that change anything.

With the splitter connected normally to both mixer disconnect the lines from the splitter that go out to the floor boxes, all of them. Then on a mic channel that buzzed with a mic connected at floor box connect that mic to the same channel only directly at the mixer and see what you get.

Was any work being done in the building at the time the hum and buzzing started?

What model splitters do you have?

With your multiple mixers in different locations opens up a greater potential for grounding loop problem, but with the correct trouble shooting, wiring and isolation that can be taken care of.

As for the installation company you brought in, based on that they could not find the problem and the suggestion of just replacing all the cable to see if that takes care of the problem I would say you need to get another company!

If the cable is the correct type of cable in the first place it's just not going to bad on it's own. Of course a mouse could have chewed through a cable or a screw or nail got ran into somewhere but that could be narrowed down before just replacing all of it.

Sam Blount

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #2 on: February 02, 2018, 10:56:07 am »

Do you have any 1/4 inch jacks mounted in the floor box that are not insulated from the box.

No, just XLR inputs and power.

Do you get buzz on the system from any of the floor box mic channels with nothing plugged into those channels?

Yes, buzzing and sometimes popping. The amount of buzz changes when a mic is plugged in. The new Shures buzz much louder.

If you disconnect the lines feeding the recording mixer does that change anything.

When I disconnect the lines going from splitter to mixer there is no buzz. Same if I unplug the xlr's from the back of the mixer.

With the splitter connected normally to both mixer disconnect the lines from the splitter that go out to the floor boxes, all of them. Then on a mic channel that buzzed with a mic connected at floor box connect that mic to the same channel only directly at the mixer and see what you get.

They go into the splitter via a phoenix connector, any easy way to do this without soldering?

Was any work being done in the building at the time the hum and buzzing started?
None that I know of.

What model splitters do you have?
Pro-Co MS 83-P https://www.bhphotovideo.com/c/product/404996-REG/Pro_Co_Sound_MS83P_MS_83P_8_Channel_2_Way.html?ap=y&c3api=1876%2C%7Bcreative%7D%2C%7Bkeyword%7D&gclid=CjwKCAiAtdDTBRArEiwAPT4y--5Kq6wrSN1kmpGW-0JO1vbf-d9wPWZ1cF3CQcXvubp-21D-rljsbhoCznUQAvD_BwE

With your multiple mixers in different locations opens up a greater potential for grounding loop problem, but with the correct trouble shooting, wiring and isolation that can be taken care of.

One thing that is strange is when I unplug an xlr from my recording mixer, I see levels coming out of the automatic mixer...

As for the installation company you brought in, based on that they could not find the problem and the suggestion of just replacing all the cable to see if that takes care of the problem I would say you need to get another company!
I know! I've been looking, believe me.

If the cable is the correct type of cable in the first place it's just not going to bad on it's own. Of course a mouse could have chewed through a cable or a screw or nail got ran into somewhere but that could be narrowed down before just replacing all of it.
Yah, I thought that too, but it's multiple floor boxes in different areas. Another thing that the company mentioned is that the cable runs could be acting like giant antennas which can cause interference...It's really been such a headache, thanks for the response. I'll try to provide as much info as I can.
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Tim Barber

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #3 on: February 02, 2018, 12:10:16 pm »

I inherited a problematic older system with lots of floor box weirdness. Ultimately we bypassed it all with CAT5 but in the interim I found one of these http://www.ratsoundsales.com/p/soundtools-xlr-snifsend.html to be extremely useful. Found lots of Pin 1 issues and other goodies. Not affiliated, just a fan.
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Mike Caldwell

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #4 on: February 02, 2018, 07:24:01 pm »

Yah, I thought that too, but it's multiple floor boxes in different areas. Another thing that the company mentioned is that the cable runs could be acting like giant antennas which can cause interference...It's really been such a headache, thanks for the response. I'll try to provide as much info as I can.

You will have to open up a floor box or take out of the floor, but check that pin 1 the shield is not connected to the outer shell of the XLR connector.

Have you tried the ground lift switches on the splitter?

How are the outputs wired, is one set on the direct outs and another on the isolated outs or are both sets of outputs each wired to an isolated output, please don't tell me that both sets of outputs are wired to the same output!

As for directly connecting to the splitter input for a test you need to make a cable with an XLR female on one end and bare wires on the other, the phoenix connector unplugs from the splitter and screws hold the wires in the plug.

If you just unplug the input phoenix connectors what happens with the buzzing then?

Now about the phantom power being applied at the splitter.
In my opinion that's not the greatist idea as it appears to just apply phantom power to every mic channel.

What happens with the buzzing if you disconnect the phantom power supplies.
Non of your condenser mics will work with out the phantom power turned on.

What model mixers are connected to each split of the system, if possible use one of those mixers to supply the phantom power, even better if the mixer has individual phantom power switches for each mic channel so you only turn on the phantom power on the channel that needs it.

Now only the mixer connected to the direct outputs will be able to supply phantom power. You may need to re patch the outs to get the correct mixer connected to the direct outputs, easy to do in your case with the phoenix connector blocks.

In most cases with a splitter system one mixer is connected to the the direct out and the other to an isolated output.

Post a picture of the back of the splitter showing the wiring.

Where are you located, maybe there's one of us close by that could help.
For some strange reason I like service calls like this one not only for the pay check but also the challenge!

« Last Edit: February 02, 2018, 09:38:57 pm by Mike Caldwell »
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Sam Blount

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #5 on: February 02, 2018, 08:28:08 pm »

I inherited a problematic older system with lots of floor box weirdness. Ultimately we bypassed it all with CAT5 but in the interim I found one of these http://www.ratsoundsales.com/p/soundtools-xlr-snifsend.html to be extremely useful. Found lots of Pin 1 issues and other goodies. Not affiliated, just a fan.

Thanks Tim!
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Sam Blount

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Re: Help Troubleshooting Setup with Floor Boxes; Splitters
« Reply #6 on: February 02, 2018, 08:45:43 pm »

Mike,

I started replying to your questions, but realized it will probably be better to do Monday morning when I'm there, because I don't want to give you any wrong info. I know the isolated and direct outs go to each separate mixer.

Quick question, on the splitter are you talking about just disconnecting the power from the back to disable the phantom power? I do have individual phantom power switches for each channel on my mixer, it's a Yamaha 02R96 V2. I'm kind of excited to try this, so I'll update Monday.

Thanks!



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