Sound off HDBaseT Links - presentations

[TomHoward]

These days it seems with installations you're dealing with an HDBaseT link between stage and projector.
The projectors never have a proper audio out though, it's usually a 3.5mm jack.

How do you deal with the audio from the laptop in a situation with a HDBaseT link when you are using a connection direct between transmitter at stage and projector? Install a stereo DI at the projector on the 3.5mm output? Convert to HDMI just for the sake of extracting the audio with a separate box?

Some of the video is fed through a matrix so there I have an extra output which is just for extracting sound. But... when it's direct HDMI transmitter to projector in a simpler solution, I can't find anything neater than a second connection to the laptop for sound, or using the noisy 3.5mm output from the projector?

[Andrew C]

If I understand the question...  I think our latest install has a box to strip audio; however, I'm just off to take MrsC to a hosp appointment.  I'll try to look tomorrow when I'm back it.

[TomHoward]

I have them that strip audio from HDMI, but struggling to find one for HDBaseT. I can find a receiver box with a separated audio output but that means changing or mismatching the transmitter. I think I'm just going to have to install a stereo DI box off the projector sound...

[Stuart91]

2 minutes ago, TomHoward said:

I have them that strip audio from HDMI, but struggling to find one for HDBaseT.

There are various options from Kramer and others that would do this, but most would be overkill for this sort of application with far more features than you need and a price tag to match. 

You could opt to use something like the VP-440x at the source, which would act as a transmitter and also give you an audio breakout. 

[J Pearce]

Use a HDMI audio de-embedder at the stage end before it hits the HDBT link? Cable it up with the lectern mic etc.

[david.elsbury]

DI the projector.

[Andrew C]

35 minutes ago, david.elsbury said:

DI the projector.

Trouble with that is that the projector is usually nailed to the ceiling, a long (inaccessible) way from where you want the sound.

 

And - ours is on the HDMI, so not much help.

[TomHoward]

I could put one at the stage end whilst it's still HDMI, but the HDBaseT sender is POE powered in the back of a wall box so it's not that accessible....
Plus one of my worries is it's another link in the video chain - so if that box failed it could take out the video I guess.

The projector is okay for accessibility in this case as there's a loft space above the ceiling that has proper cable trays etc, so I can run audio from it okay. The problem is the rack mixer isn't XLR in & doesn't have phantom power on the stereo inputs for the DI - what a nightmare. I just wish projectors had a proper audio out.

Looks like DI'ing the projector is the most likely route and I'll either have to use a passive DI or put phantom power injector on the DI - or find a DI with a battery and bodge a PSU in....

[sandall]

I've used MTR passive DIs for decades & never had cause to question their audio quality. In your circumstances I wouldn't want add another layer of potential (no pun intended) problems.

[sunray]

4 hours ago, TomHoward said:

I could put one at the stage end whilst it's still HDMI, but the HDBaseT sender is POE powered in the back of a wall box so it's not that accessible....
Plus one of my worries is it's another link in the video chain - so if that box failed it could take out the video I guess.

The projector is okay for accessibility in this case as there's a loft space above the ceiling that has proper cable trays etc, so I can run audio from it okay. The problem is the rack mixer isn't XLR in & doesn't have phantom power on the stereo inputs for the DI - what a nightmare. I just wish projectors had a proper audio out.

Looks like DI'ing the projector is the most likely route and I'll either have to use a passive DI or put phantom power injector on the DI - or find a DI with a battery and bodge a PSU in....

And what does a DI do other than isolate (possibly) and transform a signal from one state to another. Kinda reminds me of isolating transformer.

Cheap one from CPC: https://cpc.farnell.com/av-link/201-087uk/ground-loop-isolator-3-5mm/dp/AV26880?CMP=CPC-ebooks-BIGBOOK2019

Very openable to convert to balanced XLR etc Shown here directly onto CAT5

[TomHoward]

I think looking at it I'll buy one of the Interspace Industries non-usb PC balance box which is a trailing 3.5mm to 2x XLR with pads, earth lifts etc meant for attaching to the 3.5mm output of a laptop and stick it on the projector audio out.

I know it's £76 compared to a few pounds to fix it up modifying an isolator but the projector was north of 15k so it'll be alright....

[sunray]

1 hour ago, TomHoward said:

I think looking at it I'll buy one of the Interspace Industries non-usb PC balance box which is a trailing 3.5mm to 2x XLR with pads, earth lifts etc meant for attaching to the 3.5mm output of a laptop and stick it on the projector audio out.

I know it's £76 compared to a few pounds to fix it up modifying an isolator but the projector was north of 15k so it'll be alright....

Fair comments. One of the visiting bands had a similar product for a keyboard. it was fine as I recall it.

 

£15K?  A company I worked for took out a specific additional insurance for a projector late 90's to cover it from the point we took posession to transporting and fitting it until the customer paid, I think the insurance cost nearly that much and we had to keep letting them know any progress.

[david.elsbury]

@sunray the late 90s is almost 30 years ago 🤣

[sunray]

7 hours ago, david.elsbury said:

@sunray the late 90s is almost 30 years ago 🤣

OHHHhhh yes and don't I feel it. Especially after humping 12KW 3phase projectors around.

Driving a Bedford Midi van, mine was the only vehicle at the time in the company that would take it and fit into the unloading bay.

 

FWIW it cost 2.5 times our 4 bed detatched house😁 which by todays prices would be around £1.2M😒☹️

Edited September 28 by sunray