First of several questions - hum / hiss in audio

Discussions around meetinghouse sound systems, microphones, assisted listening devices, and translation equipment
dbaresrc
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First of several questions - hum / hiss in audio

Postby dbaresrc » Mon Nov 09, 2020 9:58 am

Hello. I have several questions related to building audio. Our stake center is about 10 years old. I'm not sure if that matters in terms of technology used but I share in case it does. I have several questions that I'll post here.

First question.

There is a bit of a hum and hiss in the audio. Sitting in the chapel and it's quiet you can hear it. Once someone starts speaking, the noise is covered by the voice. However, you still hear it clearly in the audio feed into the webcast. It is distracting until you force yourself to disregard it.

Any ideas or solutions to reduce or eliminate that?

Thanks

Carlton
Lewisville TX stake

russellhltn
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Re: First of several questions - hum / hiss in audio

Postby russellhltn » Mon Nov 09, 2020 10:55 am

If it's at the level of a distraction, I'd report it to FM and let them deal with it though the church's audio contractor.

The sound in the webcast could be a ground loop issue. You may want to look into putting the sound though an isolation transformer.
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superdave98
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Re: First of several questions - hum / hiss in audio

Postby superdave98 » Mon Nov 09, 2020 12:35 pm

I ran into a high-pitched noise when using the building audio for YouTube streaming. Fortunately, I was using OBS, which had noise filters. I applied the noise filter and that took care of 95% of it.

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Re: First of several questions - hum / hiss in audio

Postby russellhltn » Mon Nov 09, 2020 12:37 pm

How are you two connecting to the house system? If it's though the "record out" it's transformer isolated. If you're going though the distribution rack, you might have a ground loop or other issues.
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CalS201
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Re: First of several questions - hum / hiss in audio

Postby CalS201 » Mon Nov 09, 2020 7:11 pm

dbaresrc wrote:Hello. I have several questions related to building audio. Our stake center is about 10 years old. I'm not sure if that matters in terms of technology used but I share in case it does. I have several questions that I'll post here.

First question.

There is a bit of a hum and hiss in the audio. Sitting in the chapel and it's quiet you can hear it. Once someone starts speaking, the noise is covered by the voice.
However, you still hear it clearly in the audio feed into the webcast. It is distracting until you force yourself to disregard it.

Any ideas or solutions to reduce or eliminate that?


Hearing broad spectrum, or moderately high frequency, low amplitude hiss while sitting alone in the chapel is normal for many PA systems. Hearing low frequency(60-120hz) hum is not normal and may mean the power supplies inside the preamp and/or power amp have ripple caused by aging capacitors. In this case its time for some replacement amps.

Hearing low frequency hum ONLY in the webcast, and the webcast is getting audio from the EmTech AVDH-1 in the AV room would indicate a groundloop between the PA System and the AV room - which is usually solved with an isolation transformer installed by an audio tech.

If you are hearing "hum" in the webcast, and the audio is coming from the RecordOut jack in the chapel, you have a bad power supply in the preamp or amp.

russellhltn
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Re: First of several questions - hum / hiss in audio

Postby russellhltn » Mon Nov 09, 2020 9:03 pm

Hum can also come from improperly handled inputs. In our stake's cultural hall, they used power relays to switch audio signals. When it got bad, a bit of percussive maintenance was necessary to bring it under control. The chapel's sound system is fine.

I don't hear any hiss from either one.

I have to wonder if something like a organ or some other auxiliary input is having trouble. Also, make sure no one has turned on "satellite". That usually drops the gain of the podium and turns off the other mic inputs. It's to be used if you're receiving a satellite broadcast. (It has nothing to do with satellite speakers.)
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dbaresrc
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Re: First of several questions - hum / hiss in audio

Postby dbaresrc » Tue Nov 10, 2020 7:06 am

Thanks for all the replies. Looks like I need to do some homework . . . . and get facilities involved.

CalS201
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Re: First of several questions - hum / hiss in audio

Postby CalS201 » Tue Nov 10, 2020 7:49 am

russellhltn wrote:Hum can also come from improperly handled inputs. In our stake's cultural hall, they used power relays to switch audio signals. When it got bad, a bit of percussive maintenance was necessary to bring it under control.


:lol: Yes, very true, sometimes a good beating of relays and arm twisting of volume controls is needed to get things working again.


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