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Author Topic: Ground Loop What to do? Should I bother?  (Read 2000 times)

frank kayser

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Re: Ground Loop What to do? Should I bother?
« Reply #20 on: February 25, 2020, 10:53:33 am »

Another thing is to put an HDMI audio extractor ahead of e projector. Then the remote wonít affect the audio level and you donít have to deal with what ever quality audio path is the projector.


Ding! Ding! Ding!  We have a winnah! I didn't even think along those lines, and of course, did not know they existed.
I LOVE that idea!  I'm looking for one RIGHT NOW!
Thanks much, Rob!  A beer is waiting for you when you're in the area next!


frank



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Mike Caldwell

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Re: Ground Loop What to do? Should I bother?
« Reply #21 on: February 25, 2020, 02:12:21 pm »


Ding! Ding! Ding!  We have a winnah! I didn't even think along those lines, and of course, did not know they existed.
I LOVE that idea!  I'm looking for one RIGHT NOW!
Thanks much, Rob!  A beer is waiting for you when you're in the area next!


frank

The audio extractor prior to the projector will work however if VGA connections are still used from time to time and audio is needed you will still need a way to get audio from the computer at that time.

frank kayser

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Re: Ground Loop What to do? Should I bother?
« Reply #22 on: February 25, 2020, 03:05:19 pm »

The audio extractor prior to the projector will work however if VGA connections are still used from time to time and audio is needed you will still need a way to get audio from the computer at that time.
Yeah.  I've been thinking about that too.  Getting crowded up there by the projector.
- Audio split from HDMI box
- Radial SB5w to go balanced
- Stereo combiner (or switch) (or homerun to mixer)


Many of the Audio split from HDMI boxes offer TOSLINK - that would eliminate the Radial and the balanced line.
TOSLINK a good or bad idea in the ceiling?  (by time you count corners, maybe 40') TOSLINK to analog audio by the mixer...

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Mike Caldwell

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Re: Ground Loop What to do? Should I bother?
« Reply #23 on: February 25, 2020, 06:15:17 pm »

For the VGA needs you could get a VGA to HDMI converter, some of those have an audio to HDMI insert function.
That's getting to be a lot of adapters and converters though.

A home run audio line to the computer location with the proper interface to connect to the computer would work for any video format. The issue there would be that most computers
when connected to HDMI will automatically route the audio out to the HDMI, the requires someone being around who knows how to redirect the audio to the headphone jack or USB if your going that way.
« Last Edit: February 25, 2020, 09:07:54 pm by Mike Caldwell »
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Brian Jojade

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Re: Ground Loop What to do? Should I bother?
« Reply #24 on: February 25, 2020, 08:45:20 pm »

Another thing is to put an HDMI audio extractor ahead of e projector. Then the remote wonít affect the audio level and you donít have to deal with what ever quality audio path is the projector.

The problem you can run into with these though, is that some devices add latency with HDMI signals.  Usually the device is designed so that the delay in the audio and the delay in the video is the same.  When you start mixing and matching the decoders on devices, you can sometimes end up with undesirable results.

If you want to see a sample of this, go to any big box TV display that has multiple brands of TVs set up and fed with an HDMI splitter.  Watch for scene cuts, and you'll see how different each TV might be.  It can be quite a bit sometimes!
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Brian Jojade

Caleb Dueck

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Re: Ground Loop What to do? Should I bother?
« Reply #25 on: February 26, 2020, 01:37:10 pm »

For the VGA needs you could get a VGA to HDMI converter, some of those have an audio to HDMI insert function.
That's getting to be a lot of adapters and converters though.

Typically, assume a projector has an HDMI input.  If not, add up the cost of lamps for the next 5 years, and ask if replacing it with a laser model wouldn't make sense. 

I just had a project this week where running input(s) directly to the project, with audio back to the DSP, sort of (barely) made sense. The client asked to add one additional input, which tipped the scales to running all inputs to the video rack to a switcher, and running a single HDbaseT Cat6 to the projector.  Most projectors now also have HDbaseT, so that eliminates two failure points (separate Tx and Rx).  Audio de-embedded at the switcher and run to the mixer/DSP. 

The only times where using the projector as a switcher and audio de-embedder makes sense - classrooms, where there is a baby amplifier up there as well (in a recessed ceiling box typically) powering the speakers, no rack at all. 
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frank kayser

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Re: Ground Loop What to do? Should I bother?
« Reply #26 on: February 26, 2020, 05:17:09 pm »

Typically, assume a projector has an HDMI input.  If not, add up the cost of lamps for the next 5 years, and ask if replacing it with a laser model wouldn't make sense. 

I just had a project this week where running input(s) directly to the project, with audio back to the DSP, sort of (barely) made sense. The client asked to add one additional input, which tipped the scales to running all inputs to the video rack to a switcher, and running a single HDbaseT Cat6 to the projector.  Most projectors now also have HDbaseT, so that eliminates two failure points (separate Tx and Rx).  Audio de-embedded at the switcher and run to the mixer/DSP. 

The only times where using the projector as a switcher and audio de-embedder makes sense - classrooms, where there is a baby amplifier up there as well (in a recessed ceiling box typically) powering the speakers, no rack at all.


Good food for thought, Caleb, especially in the light of some folks complaining about image quality (especially corner sharpness and overall brightness).  I'd like to get one with a short focus lens so I can hang some stage lights in an area off limits due to the current projector beam. 
Laser, huh?  God, I love this place - always learning something!




The problem you can run into with these though, is that some devices add latency with HDMI signals.  Usually the device is designed so that the delay in the audio and the delay in the video is the same.  When you start mixing and matching the decoders on devices, you can sometimes end up with undesirable results.

If you want to see a sample of this, go to any big box TV display that has multiple brands of TVs set up and fed with an HDMI splitter.  Watch for scene cuts, and you'll see how different each TV might be.  It can be quite a bit sometimes!


I've seen many times loss of sync between the audio and visual.  I have to look away.
frank
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Rob Spence

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Re: Ground Loop What to do? Should I bother?
« Reply #27 on: February 29, 2020, 01:10:07 pm »

I discovered the hdmi extractor when I also had several inputs to the projector. My projector was about 100 cable feet from the mix position and one input was 130í from mix.
My solution was an hdmi splitter, hdcp remover, & hdmi to cat6 at the long source, back to hdmi at mix, to audio extractor, then to switcher. Moved the laptop to near mix and hdmi to switcher. Out of switcher via SDI toward projector. At projector, convert to hdmi, then to dvi (projector only had dvi & vga), then Geffen DVI detective and to projector.
This allowed me to solo the audio from the long source (a cable tv box), while seeing a preview so I could switch to it at the right time. This was a private party and the video was the Kentucky Derby. The rest of the time was background music and video from the laptop.
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Mike Caldwell

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Re: Ground Loop What to do? Should I bother?
« Reply #28 on: February 29, 2020, 09:19:02 pm »


Good food for thought, Caleb, especially in the light of some folks complaining about image quality (especially corner sharpness and overall brightness).  I'd like to get one with a short focus lens so I can hang some stage lights in an area off limits due to the current projector beam. 
Laser, huh?  God, I love this place - always learning something!


The laser beam is not what actually projects the video, the laser heats up phosphor disc white hot replacing the light bulb.

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Re: Ground Loop What to do? Should I bother?
¬ę Reply #28 on: February 29, 2020, 09:19:02 pm ¬Ľ


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