Audio Power Distribution

LPdan

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I am hanging line arrays as part of an install, and will be splitting the power evenly over the three phases. The audio processing rack is on the opposite side of the stage from the breaker panel for the speakers. However, there is another breaker panel on the processing rack side. Is there any reason to run a line from the speaker panel over to the rack instead of using the rack side panel? (Other than convenience of having all audio breakers in one place) Pros or cons?
 

Amiers

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What’s on the panel that’s closest to the rack.

Generally the reason audio is on its own panel is for clean power. If you got anything that takes a rush in like HVAC or High Bays then prolly shouldn’t use it.
 
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LPdan

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The panel near the rack has a bunch of edison outlets for general use, a clock, and some fluorescent work lights. The edisons could be used for extra LEDs, foggers, etc.
I've heard it said that in a non-3-phase system, you should try to keep all the audio on one leg of the split. I do have a line interactive UPS/surge going in the audio rack for what it's worth.
 

Amiers

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Yeah you want to try to keep it to it’s own leg of power. Those fluorescents might pose a problem but if they are for your work lights and don’t get turned on when the rack is in use you might be fine.

If there are a lot you could, and I stress could, get some line interference from the ballasts just being hot and not actually working the tubes.

As far as putting extra things on it I wouldn’t if you do use the panel. The leds have drivers in them that will give noise and a fogger will have a pump and heater that will kick on and have a rush.

Now it is all minimal and most likely won’t give you and issue most likely a very low hum. The best thing to do is try the rack on both sides and see how it sounds.
 
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FMEng

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The power source really isn't the problem. The problem is ground loop current traveling on the cable shield. Just lift the audio cable shield at the speaker inputs, and there's no ground loop. For a temporary installation use XLR M-F lifters. For a permanent installation, cut the drain wire and isolate it with shrink tubing. Always ground the shield at the output stage and lift at the input stage, and only do this on connections that are truly balanced.

Clean power for audio systems and "all on the same panel" and "all on the same phase" are mostly myths perpetuated by the lack of knowledge about properly interfacing various types of audio outputs and inputs.
 
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LPdan

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The power source really isn't the problem. The problem is ground loop current traveling on the cable shield. Just lift the audio cable shield at the speaker inputs, and there's no ground loop. For a temporary installation use XLR M-F lifters. For a permanent installation, cut the drain wire and isolate it with shrink tubing. Always ground the shield at the output stage and lift at the input stage, and only do this on connections that are truly balanced.

Clean power for audio systems and "all on the same panel" and "all on the same phase" are mostly mytsh perpetuated by the lack of knowledge about properly interfacing various types of audio outputs and inputs.
So if I lift the shield at the speaker input connector, it would not matter which panel? Would the line still be considered balanced? Is there any down side to this? The audio jumpers after the first shield down the array can keep the shield in place correct?
 

RonHebbard

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So if I lift the shield at the speaker input connector, it would not matter which panel? Would the line still be considered balanced? Is there any down side to this? The audio jumpers after the first shield down the array can keep the shield in place correct?
@LPdan ( & @FMEng ) Your "balanced line" could / should be a shielded twisted pair. ( If it's a shielded single conductor it's NOT balanced).
Your balanced line would commonly be connected via XLR3's, or RTS connectors on more compact, or "economically priced", gear.
The theory is returning any noise / interference / electro-magnetically induced hum collecting on the shield back to an output stage; the output stage is normally an appreciably lower impedance than balanced or bridging inputs AND, optimistically, the shield terminal of the output connector is bonded to the grounded metal chassis IMMEDIATELY upon entering the chassis. Per electrical codes, the metal chassis will be bonded to power / earth ground by the grounded third prong of the device's power cord. PENG Neil Muncy is possibly most remembered for his pioneering research into what became referred to as "the pin one problem". Mr. Muncy died some years ago but Googling "Neil Muncy / pin one" ought to pull up more detailed info. Mr. Muncy explained his research and findings at an AES meeting in New York I believe it was. RANE Audio will have a wealth of info' on properly interconnecting and shielding more different topologies of input, output, and inserts than you ever imagined existed.
Side note: Telephone companies commonly ran unshieled BALANCED twisted pairs for literally MILES, generally most cables you'll encounter personally will be appreciably shorter. In my broadcast daze it was common for a station's studios to be in the heart of town with their transmitter and towers well out of town where land was MUCH more affordable. In the case of Hamilton, Ontario, our studio's were downtown adjacent to the Great Lakes at essentially water level while our six tower transmitter site was in a farmer's field not only out of town but several miles away (as the crow flies) atop the Niagara Escarpment which Hamiltonian's commonly refer to as 'up the mountain'. Any serious mountain climber, or resident of the Swiss Alps, would giggle at the site of our "mountain".
The "unshielded balanced line coupling our studios to our transmitter was possibly five miles as the crow flies but at least three times that long by the time it routed through various telephone company exchanges along the way.
Toodleoo!
Ron Hebbard
 
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Amiers

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The power source really isn't the problem. The problem is ground loop current traveling on the cable shield. Just lift the audio cable shield at the speaker inputs, and there's no ground loop. For a temporary installation use XLR M-F lifters. For a permanent installation, cut the drain wire and isolate it with shrink tubing. Always ground the shield at the output stage and lift at the input stage, and only do this on connections that are truly balanced.

Clean power for audio systems and "all on the same panel" and "all on the same phase" are mostly mytsh perpetuated by the lack of knowledge about properly interfacing various types of audio outputs and inputs.
True but if you are mixing things together the first thing they do is say get off my power and when it still hums you laugh and say “I toad a so”. Easier to give them their own power PD.

Dan I should of been more clear about the grounding thing it was what I meant when talking about power. That’s why I said try it out if there is a hum you could get some ground lifts and whala it might go away or if there even will be one to begin with.
 

MNicolai

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A proper grounding scheme is the biggest issue to address.

Phases are often wrongly blamed for other issues in the system. There are different opinions about harmonics and neutral currents but the shortest answer is that it's usually only perceptible when there are other problems at play. Realistically, the vast majority of sound systems out there are on 3-phase power. A smaller slice of which are on single-phase, which minimizes harmonics because in an ideal application the phases cancel. I'm not generally aware of any sizable systems that are driven off of a single leg. It looks good on paper but in practice it's not a widespread trend because in order to perceive the difference as an audience member there are a dozen other stops you have to pull out ($$$,$$$.00) before that one pays off. Certainly in a case where you wouldn't be behind a shielded isolation transformer, the results you can expect from hopping on an existing leg with other loads on it that could include motors, HVAC, lighting, the green room garbage disposal -- it's not the first priority I would make. If FOH and convenience receptacles near the stage are not also on the same leg, what you do with the processing rack ends up being meaningless if all those other power sources are not also addressed.

There's a deep rabbit hole you can go down but like @FMEng, I'd say focus on the signal cabling for the new installation first, and worry about the existing electrical later if you perceive a problem.

I say that because the rabbit hole you can go down is deep and decisions are are of minimal cost impact in new construction can be incredibly expensive in existing installs. Will the mix console and all other AV electronics also be fed from the same panelboard or leg just because you put the processing rack on the same phase? Will there be any shielded isolation transformer in place to reduce noise from the rest of the building electrical system? Is the HVAC system loud enough in the theater that paying $50,000 or $150,000 extra to kill a few dB from your audio system's noise floor is going to make a difference? Are you driving a $750,000 speaker system with a $3,000 mixer? Are your circuit conductors properly twisted in conduit and did they avoid using MC cable when they installed the existing electrical?

I would say that on average, the majority of existing installs I've had to troubleshoot with noise issues end up coming down to a few different things:
  • Improper grounding of signal cabling at patchbays or inputs of DSP/amps.
  • Knicked signal cables that are coupling with the conduit ground.
  • Untwisted speaker wires that are introducing lots of crosstalk between systems.
  • The noise is actually coming from HVAC equipment but has been incorrectly attributed to the sound system.
Which leg the AV system is on or that the system is on 3-phase power tends not to be what makes my phone ring.
 
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JD

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Whatever you do, make sure all your audio power comes from ONE panel. An electrical fault can induce quite a bit of voltage into the ground plane of a panel before the breaker kicks off. Remember, during a fault, the ground conductor itself will have voltage drop across it. If your system is connected to two panels, this drop voltage will be imposed across the ground/shield conductors in your audio system as the juice tries to find other paths back to the service entrance. This can easily damage your equipment.
 
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LPdan

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Whatever you do, make sure all your audio power comes from ONE panel. An electrical fault can induce quite a bit of voltage into the ground plane of a panel before the breaker kicks off. Remember, during a fault, the ground conductor itself will have voltage drop across it. If your system is connected to two panels, this drop voltage will be imposed across the ground/shield conductors in your audio system as the juice tries to find other paths back to the service entrance. This can easily damage your equipment.
I follow this, but I’m this case (and I suspect many cases) it would be impossible to have every single audio component powered from the same panel. Our sound booth at FOH comes from another panel although. The orchestra pit is probably a mix of sources. Very old building. Is it just a case of minimize the number of panels as much as possible?
 

StradivariusBone

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I've often wondered if this matters as much with digital boards, where the connection from the stage box to the console will be a digital signal over ethernet. I was recently involved with replacing an analog board with a digital and a persistent hum that we could not eliminate with the analog immediately was gone with the digital. It is very probable that the hum was induced in the board itself judging by this result, but no amount of ground lifting or signal cable replacement abated it. I'm assuming ground loops over data cables are not going to present the same symptoms as analog runs, but are there things to look for in networking audio components with regard to power distribution?
 
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RonHebbard

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I've often wondered if this matters as much with digital boards, where the connection from the stage box to the console will be a digital signal over ethernet. I was recently involved with replacing an analog board with a digital and a persistent hum that we could not eliminate with the analog immediately was gone with the digital. It is very probable that the hum was induced in the board itself judging by this result, but no amount of ground lifting or signal cable replacement abated it. I'm assuming ground loops over data cables are not going to present the same symptoms as analog runs, but are there things to look for in networking audio components with regard to power distribution?
@StradivariusBone From the POV of a decrepit dinosaur from the analog / Edison cylinder era, someone who's literally NEVER laid eyes on an X32; installed an early Yamaha once and one of the newer, trendier, digital consoles that our Canadian Meyer distributor used to represent but have NEVER mixed on a digital console.
Having said the foregoing in LARGE PRINT:
Two points:
a; Analog consoles placed on top of heavy amplifier racks from the days of DC300's, Flame Linears, BGW500's , 750's and their ilk were known to have had hum problems due to magnetic coupling of the butch, iron cored, transformers within the amp' racks, especially if the amp' racks were made of wood, coupling into the input stages of the analog consoles and / or their power supply transformers and / or their inter-module ribbon cabled wiring and / or their ground references.

b; IIRC, when the X32 was first introduced, folks who were coupling digital stage boxes to their X32's with factory manufactured and pre-terminated cables were having minimal problems BUT folks rolling their own CAT5 / 5E and 6 variants were experiencing LOUD, EAR & transducer SHATTERING sudden ( and unpredictable ) BURSTS of NOISE. I believe, in the end, this was eventually traced to static electricity collecting on, and being discharged from, the various CAT cables and their shields and was resolved by installing RJ connectors with conductive metal shells which bonded the digital stage boxes to the X32's.
I COULD EASILY BE REMEMBERING THIS INCORRECTLY so bear in mind where you read it, who posted it, and how little I've charged you for it.
This was a long-running topic on ProSound's (Real names only) LAB forums. I'm certain @TimMc is very on top of this.
Toodleoo!
Ron Hebbard
 
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FMEng

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I have only had my X32 and stage box in a dozen venues or so, but I usually run the snake long distances to make shift control rooms in dressing rooms, offices, storage rooms and trucks. These are often very old buildings and most of the time the mixer is on a different panel than the stage box. I have yet to have any problem with the signal. When I used to do the same types of gigs with analog mixers, it took transformers on every cable in and out of the room.

I keep in my box of tricks an Ethercon female to female coupler and a short, unshielded Cat 5e cable to break the shield should there be a problem. Never used it.

Ron is correct that shielded cables are advisable for protection against static electricity for the X32/M32. A friend of mine was an early adopter that made the discovery and tested some solutions. Of course, static discharge is thousands of volts into signal pairs, which is a different issue than a ground loop. The computer industry has largely avoided such issues with transformer coupling, which suggests that a different circuit design by Music Tribe could have avoided the problem. They just didn't catch it before it hit the market.
 

TimMc

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Yeah you want to try to keep it to it’s own leg of power. Those fluorescents might pose a problem but if they are for your work lights and don’t get turned on when the rack is in use you might be fine.
Sorry, but the "single leg" concept has no foundation in physics. I await both a defended hypothesis and a practical demonstration where the only change is which leg(s) power the audio equipment... because I've never seen it happen in 35 years. What usually happens is there is a coincidental change in other loads connections or other loads are switched on or off...
 

TimMc

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I follow this, but I’m this case (and I suspect many cases) it would be impossible to have every single audio component powered from the same panel. Our sound booth at FOH comes from another panel although. The orchestra pit is probably a mix of sources. Very old building. Is it just a case of minimize the number of panels as much as possible?
Separate switchboards (breaker boxes) are the likely culprit because they are not at the same "equipotential" of ground bonding (which also means voltage between neutral/ground is different from each panel). When these get interconnected via the equipment grounding conductors you get hums and buzzes. This why in new work or construction I try to specify that all technical power (FOH audio, video, and power used on stage for audio and video) has a common grounding/bonding source and preferably all comes from the same panel or physically adjacent panels fed by the same transformer.
 

StradivariusBone

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This is an M32 and is running to the box and with some Dante all on UTP. I used to run data cable as a high school gig and they very rarely spec'd STP for any runs unless it was going over something that would absolutely cause interference or the client paid for the extra cost. Or if there was an issue with an installed cable dropping a lot of packets. With IP based data it's not so much of an issue unless you start having signal problems since the twisted pair tends to help reject interference as I understand it, but I don't know what sort of protocol is used in streaming to a stage box since they'll all be proprietary. I'd wager it's some sort of UDP streaming, but I've never experienced signal drop on a digital board to the degree that it manifests in sound issues. That's interesting about the X32 popping problem with the data cable.
 
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TimMc

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I have only had my X32 and stage box in a dozen venues or so, but I usually run the snake long distances to make shift control rooms in dressing rooms, offices, storage rooms and trucks. These are often very old buildings and most of the time the mixer is on a different panel than the stage box. I have yet to have any problem with the signal. When I used to do the same types of gigs with analog mixers, it took transformers on every cable in and out of the room.

I keep in my box of tricks an Ethercon female to female coupler and a short, unshielded Cat 5e cable to break the shield should there be a problem. Never used it.

Ron is correct that shielded cables are advisable for protection against static electricity for the X32/M32. A friend of mine was an early adopter that made the discovery and tested some solutions. Of course, static discharge is thousands of volts into signal pairs, which is a different issue than a ground loop. The computer industry has largely avoided such issues with transformer coupling, which suggests that a different circuit design by Music Tribe could have avoided the problem. They just didn't catch it before it hit the market.
The AES50 interface design used by Music Group in these mixers seems to have issues with getting enough grounding that STP with grounding RJ45s and Ethercon shells that bond to the grounding of the RJ45 are *required* if one needs performance not interrupted by the loss of work clock between the DL/S 16/32 and the ensuing pop and half-second mute when the system losses clock.

A brief "no, those wont work" synopsis for those who weren't following this 6 years ago: running a wire between mixer and stage box; powering both the stage box and mixer from the same outlet; lifting shield at either end of the STP; using UTP; pretending it doesn't happen.