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Author Topic: Hearing loop help  (Read 1721 times)

eric lenasbunt

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Hearing loop help
« on: July 31, 2016, 08:52:10 am »

I have the hearing loop from hell in our church. This thing is like a whack a mole mess of high pitch electronic noises.

In the past we have had issues with a 8-10k electronic whistle with certain instruments. I was able to mostly get all the sources by switching to active DI's.

Then, more recently we have had the loop inducing that squeal even when all inputs and outputs are muted. This morning it was all over the place and I finally pulled the plug on one of the loop amps and it went away. Thing is, in the past killing a different amp fixed it.

Church is a good size, 3 loop amps on 3 zones throughout the church. 
Loop amps appear to be
Hearing Loop
Contacta Model ET450

I'm driving it from a Matrix and its Y'd with an Fm hearing system as well.

Any suggestions? As I write this now I'm thinking iso transformers are a no brainier, haven't tried that yet. Anything else???

Thanks!
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Frank DeWitt

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Re: Hearing loop help
« Reply #1 on: August 01, 2016, 08:55:38 am »

I have the hearing loop from hell in our church. This thing is like a whack a mole mess of high pitch electronic noises.

In the past we have had issues with a 8-10k electronic whistle with certain instruments. I was able to mostly get all the sources by switching to active DI's.

Thanks!

Perhaps drive it and the hearing system through a distribution amp ?     I have a question as well.  Why would switching to active DIs have any effect?
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eric lenasbunt

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Re: Hearing loop help
« Reply #2 on: August 01, 2016, 01:55:50 pm »

Perhaps drive it and the hearing system through a distribution amp ?     I have a question as well.  Why would switching to active DIs have any effect?

Hmmm. DA is an option. I think I have an unused one in the back.

Active DI's with the idea that it is more difficult to "induce" noise into an active transformer than a small, cheap, passive one.

On another note one of the Contacta guys has reached out to me from the post and is helping out. I'll let you know how it turns out. Love that about the forums...
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Mike Caldwell

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Re: Hearing loop help
« Reply #3 on: August 14, 2016, 12:56:52 pm »

Try leaving the amps powered on but disconnecting their inputs from the sound system.
Also try just disconnecting the matrix out on the board that feeds the amps and the FM hearing system.

Jonathan Johnson

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Re: Hearing loop help
« Reply #4 on: August 14, 2016, 03:37:26 pm »

Does a loop surround the stage area? If so, poorly shielded dynamic pickups and transformers in DI boxes could be picking up the signal from the loop.

The stage area should be outside of an active induction loop.
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Re: Hearing loop help
« Reply #4 on: August 14, 2016, 03:37:26 pm »


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