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Author Topic: Strange hum in audio  (Read 1412 times)

Mike Caldwell

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Re: Strange hum in audio
« Reply #10 on: March 19, 2021, 01:32:25 pm »

The Rolls piece you linked to is a simple lower end AV DI box. They don't have the best transformer in them. It would be better than what your using now!

For the same money you can get the Peavey USB interface.
https://www.bhphotovideo.com/c/product/759075-REG/Peavey_USB_P_USB_P_USB_Direct.html

To use that you would need to go into the laptop audio settings and assign it to be the main audio output.
« Last Edit: March 19, 2021, 04:42:10 pm by Mike Caldwell »
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Tim McCulloch

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Re: Strange hum in audio
« Reply #11 on: March 19, 2021, 01:36:36 pm »

The easy button:  Radial Stagebug 5, mic line back to the mixer.  This ain't rocket surgery.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Bill Jones

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Re: Strange hum in audio
« Reply #12 on: March 19, 2021, 01:52:46 pm »

https://www.amazon.com/Radial-StageBug-SB-5-1-channel-Passive/dp/B00CRVWFFS/ref=sr_1_1?dchild=1&keywords=stagebug+sb-5&qid=1616175837&sr=8-1
Would this one work for me? It is for a laptop and has the 3.5mm connection. I would have to convert XLR out to RCA which goes to my sound board.
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Tim McCulloch

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Re: Strange hum in audio
« Reply #13 on: March 19, 2021, 02:01:09 pm »

https://www.amazon.com/Radial-StageBug-SB-5-1-channel-Passive/dp/B00CRVWFFS/ref=sr_1_1?dchild=1&keywords=stagebug+sb-5&qid=1616175837&sr=8-1
Would this one work for me? It is for a laptop and has the 3.5mm connection. I would have to convert XLR out to RCA which goes to my sound board.

Why do you need RCA at the console?  Are you out of XLR inputs?

Also, what's with the "conversion" of HDMI to VGA and back again, and what is accomplished by linking 2 laptops this way?
« Last Edit: March 19, 2021, 02:03:33 pm by Tim McCulloch »
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Russell Ault

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Re: Strange hum in audio
« Reply #14 on: March 19, 2021, 02:28:06 pm »

https://www.amazon.com/Radial-StageBug-SB-5-1-channel-Passive/dp/B00CRVWFFS/ref=sr_1_1?dchild=1&keywords=stagebug+sb-5&qid=1616175837&sr=8-1
Would this one work for me? It is for a laptop and has the 3.5mm connection. I would have to convert XLR out to RCA which goes to my sound board.

Those are good units; if you need stereo (which you probably don't) you'll have to adapt the TRS outputs to XLR (or use balanced cable with TRS connectors).

The output of a DI (any DI) isn't suitable for RCA inputs; you'll need to use the mic inputs on your console.

-Russ
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Bill Jones

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Re: Strange hum in audio
« Reply #15 on: March 19, 2021, 02:56:57 pm »

We are out of inputs on our Yamaha TF1. There are two additional inputs that have RCA inputs (red and white). These are the ones that come from the laptop's 3.5mm jack that goes up through the attic and then down to the Yamaha.
The video conversions is because our sanctuary is a bit old and has VGA cabling that goes from the stage, back to the Yamaha and it all goes under the floor. Most laptops today have HDMI video output, so we have to change (via a converter) to VGA. At the desk where the Yamaha is, and where the computer is, the VGA cable is changed back to HDMI to connect to the computer's capture card. I know it's not the most elegant solution, but it does work for video. It sounds like it would be easy to just run HDMI cable from the stage to the computer and then we could just get the audio from HDMI. It is possible, but would require some minor construction under the floor since the cabling passes through a barrier under the floor. The other option was to leave the HDMI/VGA/HDMI part the way it is and just run the audio up through the attic (which was quite easy).
That takes me to where I'm at now. If I can just get the SB-5 to connect from the 3.5mm input and ultimately output to the RCA jacks in the sound board, I will be a happy camper.
BTW, this is not high quality audio that we need, just audio without a hum. The audio would be from short videos and PowerPoint with embedded audio (played from a laptop on the stage).
« Last Edit: March 19, 2021, 02:59:10 pm by Bill Jones »
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Russell Ault

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Re: Strange hum in audio
« Reply #16 on: March 19, 2021, 03:00:22 pm »

{...} That takes me to where I'm at now. If I can just get the SB-5 to connect from the 3.5mm input and ultimately output to the RCA jacks in the sound board, I will be a happy camper.

Not without a preamp; passive DI outputs tend to be closer to mic-level than to line-level.

If HDMI-over-fibre is an option that'd work for you and running cable through the attic is easy, why not leave the VGA cable unused and run an HDMI-over-fibre system through the attic?

-Russ
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Tim McCulloch

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Re: Strange hum in audio
« Reply #17 on: March 19, 2021, 04:16:16 pm »

Not without a preamp; passive DI outputs tend to be closer to mic-level than to line-level.

If HDMI-over-fibre is an option that'd work for you and running cable through the attic is easy, why not leave the VGA cable unused and run an HDMI-over-fibre system through the attic?

-Russ

THIS!  Right up yonder! ^^^

If we can address the video issue, the audio solution can piggyback with VDO.  A device like the one below will loop-through your HDMI signal to your switcher/projector/whatever and allow you to extract L/R analog audio on RCA jacks.  With an HDMI fiber cable (2nd link) you have a $100 solution

https://www.amazon.com/dp/B00XJITK7E
https://www.amazon.com/dp/B07KG71K8K

On the analog audio side, a pair of ART CleanBox Pro, one on each end, would provide all kinds of ins and outs but you're still running more wire or cable, too.

Bill, you can look at it like this - changing the video cable to a powered, fiber HDMI will fix the video problem you didn't know you had (nudge, wink) and enable a $30-$50 fix for the audio problem you know you have.  You'll only run 1 cable and have fewer fiddly bits.

More thoughts on the SB-5:  if you run 2 wires from stage for left & right and use the TRS outputs, you could unbalance the line at the mixer by wiring pin 3 (ring) to RCA ground and pin 2 (tip) to RCA center pin, and jumping pin 1 (sleeve) to RCA ground.  The question is if you'll have enough level after losing 6dB to the unbalance.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Russell Ault

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Re: Strange hum in audio
« Reply #18 on: March 19, 2021, 08:14:16 pm »

{...} More thoughts on the SB-5:  if you run 2 wires from stage for left & right and use the TRS outputs, you could unbalance the line at the mixer by wiring pin 3 (ring) to RCA ground and pin 2 (tip) to RCA center pin, and jumping pin 1 (sleeve) to RCA ground.  The question is if you'll have enough level after losing 6dB to the unbalance.

Plus the (if my math is right) ~11 dB of signal loss in the DI's transformers (which is actually less than I would have guessed).

-Russ
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Dave Garoutte

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Re: Strange hum in audio
« Reply #19 on: March 19, 2021, 09:15:45 pm »

Not without a preamp; passive DI outputs tend to be closer to mic-level than to line-level.

If HDMI-over-fibre is an option that'd work for you and running cable through the attic is easy, why not leave the VGA cable unused and run an HDMI-over-fibre system through the attic?

-Russ
D'oh!  I was thinking of under the floor, but the attic is perfect.  An extractor would still work. Add a 1/8 TRS to twin RCA cable and you're done.  The fiber HDMI cable will isolate, so no DI required.
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Re: Strange hum in audio
« Reply #19 on: March 19, 2021, 09:15:45 pm »


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