ProSoundWeb Community

Church and H.O.W. Forums for HOW Sound and AV - Your Displayed Name Must Be Your Real Full Name To Post In The Church and HOW Forums => Church Sound => Topic started by: Paul Graves on August 14, 2017, 10:40:09 pm

Title: Suggestions for Hum
Post by: Paul Graves on August 14, 2017, 10:40:09 pm
Our setup:

X32 and an analog mixer located in different places and different AC circuits.

Two large powered speakers with built in two channel mixer, each again different AC circuits

Impossible to get all on one or even two AC circuits.

Each mixer has its Left and Right connected to the powered speakers.

So, I am certain it is ground loop causing hum, I ran some tests connecting and disconnecting and actually I believe there are several loops. don't want to expose the equipment to risk of damage by doing something stupid.

Solutions I am considering .
1) Putting a isolation transformer each XLR cable feeding the powered speakers.
2.) Using a barrel ground lift on each XLR cable feeding the powered speakers/


Any thoughts or experience and also what would be best with our new X32 rack?

Thanks,
Paul
Title: Re: Suggestions for Hum
Post by: Debbie Dunkley on August 14, 2017, 11:14:45 pm
Our setup:

X32 and an analog mixer located in different places and different AC circuits.

Two large powered speakers with built in two channel mixer, each again different AC circuits

Impossible to get all on one or even two AC circuits.

Each mixer has its Left and Right connected to the powered speakers.

So, I am certain it is ground loop causing hum, I ran some tests connecting and disconnecting and actually I believe there are several loops. don't want to expose the equipment to risk of damage by doing something stupid.

Solutions I am considering .
1) Putting a isolation transformer each XLR cable feeding the powered speakers.
2.) Using a barrel ground lift on each XLR cable feeding the powered speakers/


Any thoughts or experience and also what would be best with our new X32 rack?

Thanks,
Paul

Hey Paul... heads up - change your display name to your real name as per forum rules otherwise the thread may get locked. I am sure you will get excellent suggestions from the very experienced forum members here.
Title: Re: Suggestions for Hum
Post by: Stu McDoniel on August 25, 2017, 08:41:22 am
Our setup:

X32 and an analog mixer located in different places and different AC circuits.

Two large powered speakers with built in two channel mixer, each again different AC circuits

Impossible to get all on one or even two AC circuits.

Each mixer has its Left and Right connected to the powered speakers.

So, I am certain it is ground loop causing hum, I ran some tests connecting and disconnecting and actually I believe there are several loops. don't want to expose the equipment to risk of damage by doing something stupid.

Solutions I am considering .
1) Putting a isolation transformer each XLR cable feeding the powered speakers.
2.) Using a barrel ground lift on each XLR cable feeding the powered speakers/


Any thoughts or experience and also what would be best with our new X32 rack?

Thanks,
Paul
You probably have a difference of potential between earth grounds or an earth ground wiring issue
on one of your circuits.   Bring in an electrician and get your earth ground situation resolved.
Forget all the work around's ideas.
Title: Re: Suggestions for Hum
Post by: Don T. Williams on August 25, 2017, 11:07:46 am
Wasn't this thread discussed extensively in the last few weeks?  Under a different name?
Title: Re: Suggestions for Hum
Post by: Nathan Riddle on August 25, 2017, 11:09:59 am
You probably have a difference of potential between earth grounds or an earth ground wiring issue
on one of your circuits.   Bring in an electrician and get your earth ground situation resolved.
Forget all the work around's ideas.

This would be the safest and most correct way to do things and I HIGHLY encourage this.

Read this document:
http://www.rane.com/note110.html

AFTER you have read the above. Then proceed to the below solution:

If you have very little money then use these:
http://www.radialeng.com/icecube.php

Hint: there are dealers on the forum that can get you equipment for less; post in the marketplace saying: "WTB: Radial IceCube"

Here's another informational note I encourage reading! Heck, read them all :) http://www.rane.com/note151.html
Title: Re: Suggestions for Hum
Post by: Ivan Beaver on August 25, 2017, 08:12:02 pm
Try lifting pin 1 on the SPEAKER side of the XLR.  Leave it hooked up on the send side.

That is much better than trying "fancy hum eliminators".
Title: Re: Suggestions for Hum
Post by: g'bye, Dick Rees on August 25, 2017, 08:36:30 pm
Wasn't this thread discussed extensively in the last few weeks?  Under a different name?

Same name, different forum section:  AV.

Sometimes when a system hums it simply means it doesn't know the words...
Title: Re: Suggestions for Hum
Post by: Mike Caldwell on August 26, 2017, 08:45:39 am
Have you disconnected every input and every output from the mixer except the main left & right. If so did you still have hum in the system?
Title: Re: Suggestions for Hum
Post by: Kevin Graf on August 26, 2017, 08:55:28 am
The usual cause of the problem is a component with the dreaded 'pin 1 problem'.
The work-around is lifting the pin 1 shield at the receive end of the cable. You can make some short cable extensions to test that.
Title: Re: Suggestions for Hum
Post by: Mike Caldwell on August 26, 2017, 05:30:35 pm
The usual cause of the problem is a component with the dreaded 'pin 1 problem'.
The work-around is lifting the pin 1 shield at the receive end of the cable. You can make some short cable extensions to test that.

My service call tool kit has a couple pin 1 lift short cables in it all the time as well as my production work trunk.

Another common hum source is from audio connections from video equipment/computers.
That kind of goes back to my earlier suggestion to disconnect all other input and output connections from the mixer except the mains just to help isolate and narrow down the hum source/path.
Title: Re: Suggestions for Hum
Post by: Nathan Riddle on September 01, 2017, 09:48:21 pm
Try lifting pin 1 on the SPEAKER side of the XLR.  Leave it hooked up on the send side.

That is much better than trying "fancy hum eliminators".

Good point, thanks for pointing that out. For some reason, I was thinking it wasn't safe, but that's with ground lifting the AC ~silly me~ *shrug*

Though the Radial 'fancy hum eliminator' has a unity transformer providing more than a simple ground lift. Though I'm not sure of a scenario that would benefit the end user...?