power and multicore in trunking question

[bobmurphy]

hi - my original post is here - http://www.johnlsayers.com/phpBB2/viewt ... =1&t=14983 - ( explains that this is not a studio but a small church installation )


we have an engineers platform at the rear and the stage at the front - we want to run the multicore and speakers between both - however in addition to this we need to run several cat5 lines and power to the stage. We are putting the cables in some kind of shielded trunking, or so our electrician says. He seems to have used them for offices before and he says they have different shielded compartments for power and data. I am not so sure that the shielding that would cover data cables would be enough to protect the multicore and speakers from the power and data - has anyone any experience of this or advice - also even if we determine that power and data needs to be in it's own trunking then i will also need to find out how far apart the two would need to be

thanks

[bobmurphy]

i could really do with help on this - did i ask something wrong or anything ?

[gullfo]

Maybe John Brandt will stop by. He usually recommends running all the wires together to create a zero loop condition.

[bobmurphy]

thanks glen - i have to make the recommendation tomorrow - at the moment the best information i can find anywhere is to keep parallel power and data ( i can only assume audio and speaker is similar ) apart - so im looking at recommending putting power and data in one trunk and audio and speakers in a second separated by 300mm of concrete - had never heard of "zero loop"

[AVare]

Sorry I did not read this earlier. Regarding the need for shielding/isolation between power and mic cables (the most extreme case) outdoor live events regularly run 50 m of power and mic in a snake close together.

Andre

[bobmurphy]

thanks Andre, thats what i had thought but when i built my studio a couple of years ago i am almost certain i read material on the need for separation between the two when they needed to run parallel - any comment ? - ( maybe this i more necessary for studio than live or something)

also you mentioned that power vs audio was the most severe case - are you fairly sure of this ? - eg that compared with network (cat5) vs audio i was wondering if the squarewaves ( i presume they're square waves ) could affect the audio because the trunking (i think) has only 2 compartments so i guess i'd need to put the power in one so that would mean the mics, speakers and data in the other with no shielding apart from the mic lead shielding itself

[Soundman2020]

also you mentioned that power vs audio was the most severe case - are you fairly sure of this ? - eg that compared with network (cat5) vs audio i was wondering if the squarewaves ( i presume they're square waves ) could affect the audio because the trunking (i think) has only 2 compartments so i guess i'd need to put the power in one so that would mean the mics, speakers and data in the other with no shielding apart from the mic lead shielding itself

If it is any help, I often have to run a couple of dozen stage lighting cables close to my audio snake at live events. Those lights are on dimmers, and the electrical noise coming off those things must be pretty drastic when they are dimmed. I very rarely get any hum from that setup. The few times I've had hum, it has been due to grounding issues, shared power circuits, and once or twice due to some "clever" musician deciding it was easier to plug his guitar amp into the lighting circuits, "because it was much closer than the plug you told me to use...".

You shouldn't have too much of a problem in your setup. Balanced audio cable is, by nature, highly resistant to interference.

[bobmurphy]

thanks - in the end we arranged with the builder to have 3 ducts ( about 3" by 4" ) in the concrete floor, with about 300mm between them - it might be overkill but because it's an installation we dont have the option of changing it ..... also we wont be installing the pa for testing until after it's all carpeted etc ( and a less than a week to go to opening ) ... so hopefully there wont be hum - thanks for everybody's help