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Author Topic: Power/Mic Line Separation  (Read 8161 times)

Andre Vare

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Power/Mic Line Separation
« on: April 21, 2011, 03:31:05 pm »

I am involved in several forums about recording studio design.  A question that pops up semi-regugarly is how close can mic lines be to power lines.  I constantly give th example of outdoor concerts where the stage to FOH run has mic, power, line level, DMX and others in close proximity to each other, up to being taped together. 

In order to simplify answering, I included a poll type response.  Addtional comments are more than welcome.

When doing stage to FOH cable runs how close do you have the audio snake to the power lines?

T Taped together
0 0-2"
2 2-4"
4 4-8"
8 8-16"
M More than 16"
S Separate runs

Thanks.

Andre
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John Roberts {JR}

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Re: Power/Mic Line Separation
« Reply #1 on: April 21, 2011, 03:39:31 pm »

This is not a simple single distance spacing answer but depends on
A- the quality of wire used (uniformity of wrap and shielding)
B- angle of attack (parallel vs. normal, vs. other
C- the quality of the preamps (CMRR)
D- nature of power lines (120 vs 240, clean vs dirty, dimmers etc).
E- noise floor requirement of application.

JR


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Chris Hindle

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Re: Power/Mic Line Separation
« Reply #2 on: April 21, 2011, 04:43:24 pm »

Under 150 feet, T
Over 200 feet, S
If over 150 or so, I try to get mic and drive lines on one side, and power on the other. It doesn't always work out that way though.

Chris.
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Justin Bartlett

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Re: Power/Mic Line Separation
« Reply #3 on: April 21, 2011, 05:00:18 pm »

I am involved in several forums about recording studio design.  A question that pops up semi-regugarly is how close can mic lines be to power lines.  I constantly give th example of outdoor concerts where the stage to FOH run has mic, power, line level, DMX and others in close proximity to each other, up to being taped together. 

In order to simplify answering, I included a poll type response.  Addtional comments are more than welcome.

When doing stage to FOH cable runs how close do you have the audio snake to the power lines?

T Taped together
0 0-2"
2 2-4"
4 4-8"
8 8-16"
M More than 16"
S Separate runs

Thanks.

Andre

John Roberts makes a good point, especially in that noise floor requirements may be different between a live event and a recording studio.
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Tom Young

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Re: Power/Mic Line Separation
« Reply #4 on: April 21, 2011, 05:53:25 pm »

John Roberts makes a good point, especially in that noise floor requirements may be different between a live event and a recording studio.

They ARE very different.

Ambient noise at a live show is much higher than that in even a fairly amateurishly "designed" home studio. This noise will mask much/all of the system noise that would be very evident in a recording studio.

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Bennett Prescott

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Re: Power/Mic Line Separation
« Reply #5 on: April 21, 2011, 06:19:46 pm »

Live audio is not recording studio audio. Everyone tapes their FOH runs together, power and signal, line level or mic level.
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Andre Vare

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Re: Power/Mic Line Separation
« Reply #6 on: April 21, 2011, 07:06:25 pm »

Thanks everyone so far.  The differences between professional live sound and amateur recording are well known.  This is a straw poll and YMMV, or perhaps more accurately the results are an average.  Like an average presenting one aspect of powering in isolation.  Or maybe the average human being, with one ovary and one testicle.   :o

Beyond what John wrote the significant factor for EMI is current, not voltage. 

Of course if anything live power is going to be dirtier.

Background noise is significant in live sound.  On that point, and this is not a rhetorical question, how often have you made board recordings, either mix or isolated inputs and found unacceptable tracks due to power line related or suspected noise?  Some Midas consoles even have separate level controls on direct outs for recording.

As I wrote in the original post, additional comments are more than welcome.

An extra thanks to the people who posted and did answer the straw poll question in their responses.

Andre
« Last Edit: April 21, 2011, 07:08:49 pm by Andre Vare »
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Randall Hyde

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Re: Power/Mic Line Separation
« Reply #7 on: April 21, 2011, 07:25:25 pm »



When doing stage to FOH cable runs how close do you have the audio snake to the power lines?

T Taped together
0 0-2"
2 2-4"
4 4-8"
8 8-16"
M More than 16"
S Separate runs

Thanks.

Andre

Switched to digital. Now I run power lines alongside Cat 6 :)

Seriously, though, I'm looking at one of the new Whirlwind snakes that run two CAT6 lines along with 6 multicore pairs (for talkback, CD players, etc., at FOH). I'd probably set that in the 0-2 range in the list above as I'd just drop the two cables in the same gutter that leads to FOH (most of my shows are street festivals).  Never really had a problem with noise running a 12GA power cord alongside a snake to FOH in my old analog system. 95% of the time, any noise in the system was from dimmer packs (dirty power) or the musician's gear. The other 5% of the time it was ground loops.
cheers,
Randy Hyde
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Mac Kerr

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Re: Power/Mic Line Separation
« Reply #8 on: April 21, 2011, 08:26:54 pm »

I am involved in several forums about recording studio design.  A question that pops up semi-regugarly is how close can mic lines be to power lines.  I constantly give th example of outdoor concerts where the stage to FOH run has mic, power, line level, DMX and others in close proximity to each other, up to being taped together. 

Are you asking about the recording studio scenario, or the live event scenario? The answers are different for each environment. Live sound with an audience, all signal levels in separate cables taped together is fine. In a studio, separate conduit for each signal level, a couple of inches apart.

Mac
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James Boutilier

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Re: Power/Mic Line Separation
« Reply #9 on: April 22, 2011, 10:37:35 am »

In a studio, separate conduit for each signal level, a couple of inches apart.

Mac

+1.  In the design of modern performing arts facilities, the infrastructure is frequently used for both live sound and recording.  Different signal levels are run in separate metallic conduit and separated by several inches.
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ProSoundWeb Community

Re: Power/Mic Line Separation
« Reply #9 on: April 22, 2011, 10:37:35 am »


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