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Author Topic: No more noise?  (Read 3580 times)

Aaron Maurer

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No more noise?
« on: November 26, 2016, 07:51:55 am »

I have recently moved to a Behringer X32 full console from a Presonus 24.4.2. I provide exclusive to a venue that in the past I had to run FOH power from the stage due to the 60hz hum. I decided through a friends recommendation to use the power at FOH just to try and see if the hum goes away with the new console. Well it sure did and I am puzzled by this. The system is just flat out quite no noise. Please educate me as I am just ecstatic not having to run 100' of SO cable back or better yet not having to pack it at the end of the event.
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John Roberts {JR}

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Re: No more noise?
« Reply #1 on: November 26, 2016, 09:12:17 am »

It's working properly?

JR
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Mike Sokol

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Re: No more noise?
« Reply #2 on: November 26, 2016, 06:55:07 pm »

I have recently moved to a Behringer X32 full console from a Presonus 24.4.2. I provide exclusive to a venue that in the past I had to run FOH power from the stage due to the 60hz hum. I decided through a friends recommendation to use the power at FOH just to try and see if the hum goes away with the new console. Well it sure did and I am puzzled by this. The system is just flat out quite no noise. Please educate me as I am just ecstatic not having to run 100' of SO cable back or better yet not having to pack it at the end of the event.

Was it ground loop hum between the console and the power amps, or hum between the console and a stage input? That is, did it hum with the main faders on the console all the way down (amp hum), or when a specific input fader was on (stage input)? Also, I assume there's no digital snake, correct?
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Mike Sokol
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Aaron Maurer

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Re: No more noise?
« Reply #3 on: November 27, 2016, 09:39:20 am »

No digital snake but will have one by the end of the year. You think the hum will return with adding the digital snake?  That said the hum existed with all faders down on the Presonus last time I tried power from FOH position. I used an analog snake when the problem occurred before and used analog last night with the X32 powered at FOH. Not a peep of noise. I have the opertunity to pull cat5 to FOH and the venue has also agreed to pull 110v power from the stage area to FOH position. I am going to take them up in that.
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Mike Sokol

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Re: No more noise?
« Reply #4 on: November 27, 2016, 10:45:18 am »

No digital snake but will have one by the end of the year. You think the hum will return with adding the digital snake?  That said the hum existed with all faders down on the Presonus last time I tried power from FOH position. I used an analog snake when the problem occurred before and used analog last night with the X32 powered at FOH. Not a peep of noise. I have the opportunity to pull cat5 to FOH and the venue has also agreed to pull 110v power from the stage area to FOH position. I am going to take them up in that.

Remember that Behringer recommends using CAT5-STP (Shielded Twisted Pair) not CAT5-UTP (Unshielded Twisted Pair) for connection to their digital snake. And yes, you can certainly create analog ground loop hum with an X32 on their digital snake. I know because I accidentally did it in a theater last year doing exactly what you did by plugging into a convenient outlet at the console position, but with a digital snake. Remember if they do pull a new 120-volt receptacle to your FOH position that it really should have a isolated ground which is bonded to the ground in the same service panel as your power amplifiers and backline power. I assume they'll need to run armored cable or conduit, so if that's the case you'll probably need them to add a fourth green/yellow technical ground wire in that run so the EGC ground wire can be bonded to the metal junction box and your FOH ground isn't bonded to local building steel. Remember to use an isolated ground receptacle for FOH power.  At least that's what we had to do in Baltimore last year to satisfy the inspector and it worked perfectly. However at a church in Texas they were allowed to use the conduit itself as the EGC ground and pull an isolated "Technical Ground" wire to the FOH console power with an Isolated Ground receptacle. That also worked perfectly to stop the ground loop hum they had struggled with for years. 
« Last Edit: November 27, 2016, 11:24:44 am by Mike Sokol »
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Mike Sokol
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Kevin Graf

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Re: No more noise?
« Reply #5 on: November 28, 2016, 07:54:56 am »

Does all the equipment bass the John Windt 'Hummer Test' ?
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Mike Sokol

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Re: No more noise?
« Reply #6 on: November 28, 2016, 09:13:15 am »

Does all the equipment bass the John Windt 'Hummer Test' ?

I don't bother with that test except on the bench since most churches or small clubs aren't going to replace existing consoles, amps or powered speakers to fix their hum problems. I'm mostly concerned with actual ground loop currents, and an easy passive test is to put a clamp-ammeter around the XLR cables. No need to split out the shield from the twisted pair, and you can test multiple XLRs or the entire snake at one time. There's a lot of gear with the pin-1 problem that will hum with less than 100mA of ground loop current, some as low as 10mA or 20mA. This is a great way to separate the wheat from the chaff to see the path that the ground loop current is taking. That gives you a hint as to how to correct it either via a pin-1 lift, audio isolation transformers, or isolated ground outlets with a technical ground panel.
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Mike Sokol
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Kevin Graf

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Re: No more noise?
« Reply #7 on: November 28, 2016, 12:46:53 pm »

A sensitive clamp-on ammeter is an excellent test, but it costs way more than a Windt Hummer Tester.
And it tests the situation at hand rather than individual components. So a setup can measure good until something gets changed.
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Mike Sokol

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Re: No more noise?
« Reply #8 on: November 28, 2016, 03:38:46 pm »

A sensitive clamp-on ammeter is an excellent test, but it costs way more than a Windt Hummer Tester.
And it tests the situation at hand rather than individual components. So a setup can measure good until something gets changed.

True, but I need to know exactly what's happening in the situation at hand. That way I can do a global fix that will work with anything plugged in at a future gig. Plus a clamp-ammeter can be had for less than $50 that will go down to 10 mA resolution, and that's good enough for this kind of testing: https://www.lowes.com/pd/Southwire-Digital-Clamp-Meter/50125835
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Mike Sokol
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