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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Roland Clarke on June 26, 2019, 08:01:43 AM
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Does my digital console, when using the digital stage box, need to have the power sourced from the same circuit as the main pa, or will any supply local to the console do? :D
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Any power source will do, you don't get ground loop issues over AES50 like you do on a analog snake.
Note that this does not prevent a ground loop from being input into the snake from whatever is plugged into it. So if your snake is getting hum from someone's laptop charger on stage, it's still going to come through your mix unless you take the proper ground lift precautions.
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Any power source will do, you don't get ground loop issues over AES50 like you do on a analog snake.
Note that this does not prevent a ground loop from being input into the snake from whatever is plugged into it. So if your snake is getting hum from someone's laptop charger on stage, it's still going to come through your mix unless you take the proper ground lift precautions.
The laptop problem, is a given, I was just interested if the aes ground was tied to say the pre-amp ground. Of course their would be the same potential issue of say running an iPod or desk end microphone backwards. I’ve never worked in a situation where I have ever had to use a separate power option at the desk end, however, from a cabling point of view it would have significant advantages. I have, however, seen many instances of people having problems trying to do that with analogue consoles and not understanding why. 😁
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The laptop problem, is a given, I was just interested if the aes ground was tied to say the pre-amp ground. Of course their would be the same potential issue of say running an iPod or desk end microphone backwards. I’ve never worked in a situation where I have ever had to use a separate power option at the desk end, however, from a cabling point of view it would have significant advantages. I have, however, seen many instances of people having problems trying to do that with analogue consoles and not understanding why. 😁
Yeah, it's not a problem solver per-se, but it does introduce a fair amount of convenience as long as there aren't any analog connections needing to talk back and forth between the stage and FOH.
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After having the stage power go out and back on, causing a rather loud pop when the stage box rebooted, I keep it on it's own UPS. It lives in the road case with the stage box, so no extra handling required. FOH has one too, so the console/stagebox combo stay running if there's a power issue.
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After having the stage power go out and back on, causing a rather loud pop when the stage box rebooted, I keep it on it's own UPS. FOH has one too, so the console/stagebox combo stay running if there's a power issue.
Yeah we did the same shortly after I demonstrated what happened when one or the other lost power unexpectedly. $300 worth of UPS well spent.
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Any power source will do, you don't get ground loop issues over AES50 like you do on a analog snake.
What about MADI, Dante, GigaACE, etc? ;)
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What about MADI, Dante, GigaACE, etc? ;)
Anything that uses a standard Ethernet hardware interface, whether it use the protocol or not is transformer isolated or isolated by glass.
Mac
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Anything that uses a standard Ethernet hardware interface, whether it use the protocol or not is transformer isolated or isolated by glass.
Mac
Glass do course is the perfect isolator, 😁 I was pretty sure all was good on this front, however I’m aware that cat 5/6 is screened and wondered which potential it would ‘potentially’ balance itself too. I didn’t get to do it, but I was on a small local festival site where I could run 100m of cat 5 and I didn’t particularly fancy running 100m of mains if it was unnecessary when not 10m away there was another power source. It was the point of using something like foh microphone or playback that was the only thing I could see had any chance of being a problem. Thanks for all the replies. 😁
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Hi Roland-
In my world we don't count on power being available or it being on the same service (or the outlets wired correctly) so we run AC mains to FOH. It's a no-brain deal as the cable is taped to the drive snake. Power is *always* available.
I started doing this 35 years ago back in the days of analog desks and massive "Pin 1 problems" and have found no reason to change it.
Say I take power for FOH that's "local". I have no idea what else is on the circuit or who has access to any other outlets. I don't know who has access to the circuit breaker or even where it's located. Those are things that give me heartburn because IF something goes wrong we're not able to immediately fix it.
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I started doing this 35 years ago back in the days of analog desks and massive "Pin 1 problems" and have found no reason to change it.
Say I take power for FOH that's "local". I have no idea what else is on the circuit or who has access to any other outlets. I don't know who has access to the circuit breaker or even where it's located. Those are things that give me heartburn because IF something goes wrong we're not able to immediately fix it.
Ha!
Back in the "real console" days, if you were to go local at FOH, and somebody plugged in a lightbulb on the same circuit, you'd know it pretty quick.
Today's loads are a lot "easier", but out of habit, a distro goes out, and EVERYTHING is supplied by the distro. Stage, backline, squints, and FOH.
Chris.
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Ha!
Back in the "real console" days, if you were to go local at FOH, and somebody plugged in a lightbulb on the same circuit, you'd know it pretty quick.
Today's loads are a lot "easier", but out of habit, a distro goes out, and EVERYTHING is supplied by the distro. Stage, backline, squints, and FOH.
Chris.
Yep, and to expand on that...
If there is a failure we know *exactly* where to look - we know which distro, which breaker(s), and how the cable path runs. If the issue presents during setup we can troubleshoot in a few seconds, not waiting on the building engineer or facility maintenance person to show up with keys...
Being *fully* self contained means we're only at the mercy of our own workmanship and product selections.
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While the Cat-5 is transformer isolated balanced pairs, the shield is not!
If there is a significant difference in ground potentials across the cable, current will flow on the shield. Might be significant current.
While the remote stage box is unlikely to produce ground loop induced hum, it still may be susceptible to static discharge noise (see many pages of threads on X32 issues).
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While the Cat-5 is transformer isolated balanced pairs, the shield is not!
Good point! I suppose the shield could be broken (at one end) with a capacitor, or maybe a TVS type of device, that is sized to help with ESD while keeping power-line ground currents sufficiently small. Better to use UTP if you can so that you're truly isolated up to the breakdown voltage of the transformers.
I have taken advantage of a UTP-only connection to FOH on a few occasions, but all were indoors in modern buildings with good electricals. -F
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Good point! I suppose the shield could be broken (at one end) with a capacitor, or maybe a TVS type of device, that is sized to help with ESD while keeping power-line ground currents sufficiently small. Better to use UTP if you can so that you're truly isolated up to the breakdown voltage of the transformers.
I have taken advantage of a UTP-only connection to FOH on a few occasions, but all were indoors in modern buildings with good electricals. -F
You see, when I posted this it did occur to me that it wasn’t necessarily a cut and dried case! 😁 I’ve always done as Tim says running power from my own distro system, star earthing everything, but I’ve got enough time in the business to know this was best practice and even recently there have been a couple of threads on here with very obvious differences in ground potential problems. Of course with digital there are many reasons why in certain circumstances you could get away with this, glass being one and potentially any situation where it is only a digital signal and no analogue. What about lifting the shield on one end of the cat 5, would that reduce your transmission distance? How about lifting the earth on the desk? With the low power in use with a digital desk, does that present any significant risk, particularly if you have the shield on the cat 5 offering a ground?
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Being *fully* self contained means we're only at the mercy of our own workmanship and product selections.
I've learned that anything I don't provide is something I can't fully trust.
Shoot, I don't even fully trust my own stuff, but at least I know its idiosyncrasies and if something goes wrong, I don't have to look to someone else for the fix.