Fiber optic hdmi cable to break audio ground loop?

[ggunn]

The DI should take care of that, at least the good ones do.

Usually it's a switch to either lift the ground or not.

 

[ggunn]

One lesson I have to learn repeatedly is to try the simple/easy/cheap solutions first. Isolate the audio ground from the rest of the system with a balanced line with the shields separated and see if that solves the problem before going off to esoteric HDMI solutions.

 

[markebenson]

More clarification and a block diagram.

We do not care about 4k. The rack system is optimized for 1080p. Neither Direct TV ( network provider) or any of the DJ software offers any material higher than 1080p. The tvs are 4k but this resolution will likely never be used in their lifetime. Little 4k material is available for a business purpose. 4k tvs seem to be way ahead of their time in relation to 4k material being avialable to view on them. This part may be off topic to my problem.

The extender uses (2) cat 6 as shown in the diagram. I prefer this method as it does not require any additional power supplies on either end. The video transmission is flawless.

Direct box - I brought a direct box last night to test. First connecting it between the house mixer and the audio rack and noise still present.

I then connected the direct box between the djs laptop and the house mixer and we are clear, no noise.

THE PROBLEM WITH THIS SOLUTION IS -

Djs often bring their own mixers. Effectively the dj would have to have have their own direct box or audio isolation method between their laptop and their mixer to make this work if they are connecting HDMI as well with the laptop. ( PLease do not
comment the Dj should have the right equipment! The talent has what they have and the bar has to make it work. They are not going to fire a Dj for not having a quality audio card when the bar rang $2000 more this event get it?).



In the drawing i have noted in red the 2 spots I was considering changing the standard hdmi cable for a fiber optic one.

Thanks for your input!

 

[synchro]

I think most of the fiber optic HDMI cables are a hybrid type where there are still copper wires for control purposes which include a ground return, and so they may not provide the isolation you need. "HDMI extender over fiber" modules are connected only by fiber and therefore should provide good isolation.

 

[ggunn]

I think most of the fiber optic HDMI cables are a hybrid type where there are still copper wires for control purposes which include a ground return, and so they may not provide the isolation you need. "HDMI extender over fiber" modules are connected only by fiber and therefore should provide good isolation.

Likewise, there are wireless solutions:

https://www.amazon.com/dp/B08DCT337B/ref=as_li_ss_tl?SubscriptionId=AKIAJO7E5OLQ67NVPFZA&ascsubtag=652685366-2-1086952776.1638723250&tag=shopperz_origin1-20

 

[zbang]

If putting the DI between the laptop and mixer (while the HDMI is connected) produced the same noise, I'd immediately suspect that DI; which one are you using? (I'm a fan of the Whirlwind products, and their IMP2 box; the Samson ones are supposed to be pretty good, too.)

 

[ggunn]

If putting the DI between the laptop and mixer (while the HDMI is connected) produced the same noise, I'd immediately suspect that DI; which one are you using? (I'm a fan of the Whirlwind products, and their IMP2 box; the Samson ones are supposed to be pretty good, too.)

And the DI needs to have ground lifting capability. Some do not.

But if the noise is entering the signal before the DI, the DI will not remove it.
.

 

[Todd0x1]

Use something like this to isolate that stage input from your house mixer, install it such that it won't get bypassed or removed.

PI-2XX | Jensen Transformers

The design begins with a rugged flanged enclosure that comes standard with gold plated XLRs and a removable screw-down barrier strip for easy installation in NEMA enclosures. Plug and play easy to use, this passive interface does not require any power to work. Inside are two Jensen high...

www.jensen-transformers.com

Then have something like this for when your stage input is something other than a balanced line level source

ProAV2 - Radial Engineering

The ProAV2 is a 2-channel passive direct box designed specifically with AV integrators in mind, with multiple input connectors to easy interface with any audio source device.

www.radialeng.com

I'm pretty sure with the audio isolation between a DJ's mixer and the house system, it wouldn't matter that the DJs laptop is plugged directly into his mixer since the mixer is isolated from the house system.

 

[Todd0x1]

I'll add that if you isolate the HDMI and not the audio, you are still susceptible to noise if the DJ mixer has a grounded power cord or another path to ground.

 

[markebenson]

THe

Use something like this to isolate that stage input from your house mixer, install it such that it won't get bypassed or removed.

PI-2XX | Jensen Transformers

The design begins with a rugged flanged enclosure that comes standard with gold plated XLRs and a removable screw-down barrier strip for easy installation in NEMA enclosures. Plug and play easy to use, this passive interface does not require any power to work. Inside are two Jensen high...

www.jensen-transformers.com

Then have something like this for when your stage input is something other than a balanced line level source

ProAV2 - Radial Engineering

The ProAV2 is a 2-channel passive direct box designed specifically with AV integrators in mind, with multiple input connectors to easy interface with any audio source device.

www.radialeng.com

I'm pretty sure with the audio isolation between a DJ's mixer and the house system, it wouldn't matter that the DJs laptop is plugged directly into his mixer since the mixer is isolated from the house system.

I'll add that if you isolate the HDMI and not the audio, you are still susceptible to noise if the DJ mixer has a grounded power cord or another path to ground.

Thank you for your input.

______________________________________________________

DI box does have ground lifts. They did not change anything. I tried the DI box in 2 different places:

1- The DI box between the house mixer and the IT rack - noise still present.
2- The DI box between the laptop and the house mixer - eliminated the noise. (As mentioned future djs or bands will bring thier own mixer so this is not a permanent solution).

 

[markebenson]

If putting the DI between the laptop and mixer (while the HDMI is connected) produced the same noise, I'd immediately suspect that DI; which one are you using? (I'm a fan of the Whirlwind products, and their IMP2 box; the Samson ones are supposed to be pretty good, too.)

The noise was gone when I put the box between the laptop and the house mixer, The noise is present when I put the box between the mixer and IT rack.

 

[Todd0x1]

2- The DI box between the laptop and the house mixer - eliminated the noise. (As mentioned future djs or bands will bring thier own mixer so this is not a permanent solution).

The mixer DJs or Bands bring gets plugged into the house mixer right? The two pieces I listed above will take care of pretty much every scenario of outsiders plugging their gear into the house PA.

 

[zbang]

2- The DI box between the laptop and the house mixer - eliminated the noise.

That's the correct place for it.

(As mentioned future djs or bands will bring thier own mixer so this is not a permanent solution).

So you plug their mixer into the DI. The point is- get some isolation in there!

 

[markebenson]

The mixer DJs or Bands bring gets plugged into the house mixer right? The two pieces I listed above will take care of pretty much every scenario of outsiders plugging their gear into the house PA.

You have some good suggestions and yes the entertainment will plug into the house mixer which is at the stage. Say we isolate the house mixer output from the pa and then we isolate the performer's input between their equipment to the house mixer. I would ask if it would still be possible for ground noise to be generated on their end between their laptop, their mixer, their monitors, etc when pluggin into our hdmi and then the noise be broadcast to our system outside of the isolation.

 

[Todd0x1]

You have some good suggestions and yes the entertainment will plug into the house mixer which is at the stage. Say we isolate the house mixer output from the pa and then we isolate the performer's input between their equipment to the house mixer. I would ask if it would still be possible for ground noise to be generated on their end between their laptop, their mixer, their monitors, etc when pluggin into our hdmi and then the noise be broadcast to our system outside of the isolation.

I don't think you need to isolate between the house mixer and the PA, just between the 3rd party gear and the house mixer.

 

[markebenson]

I don't think you need to isolate between the house mixer and the PA, just between the 3rd party gear and the house mixer.

ok I understand your suggestion

again if I Isolate as you suggested would it still be possible
for ground noise to be generated on the band /dj end between their laptop, their mixer, their monitors, etc when plugging into our hdmi and then the noise be broadcast via audio to our system outside of the isolation?

 

[markebenson]

ok I understand your suggestion now

again if I Isolate as you suggested would it still be possible
for ground noise to be generated on the band /dj end between their laptop, their mixer, their monitors, etc when plugging into our hdmi on their side of the isolation and then the noise be broadcast via audio to our system anyway?

 

[ggunn]

I'll just add that ground loops and the resultant noise can be elusive and require trying alternatives until you conquer them. Ground lifting of AC powered components is to be discouraged, of course, but I have encountered situations where it was the only solution at my disposal that worked.

 

[zbang]

Something that hasn't come us is that regardless of regardless of the output of the house mixer being called "balanced", it may not actually be isolated nor may be receiving equipment in the IT room; lots of stuff is "active balanced" and doesn't involve a proper transformer (like a Jensen or even a Sescom). When I was doing a lot more portable PA work, I carried a pair of WeCo 119c repeat coils* with XLR leads as problem solvers; work like a champ.

If the IT room equipment isn't actually transformer isolated from the stage, just do it; the cost in parts will be much less than the cost in hassle over time.

*that's a 600:600 ohm transformer, pretty much flat from 30Hz to 15k, and doesn't saturate at 40dbm. Also weighs 3-4 pounds.

 

[Todd0x1]

Most audio gear these days does not have transformers except maybe on mic inputs on higher end consoles. So yes sometimes isolation by external means is necessary in applications such as OP's.