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Author Topic: How long can a mic signal travel.  (Read 9615 times)

Dave Potter

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How long can a mic signal travel.
« on: May 18, 2011, 01:20:31 pm »

Sorry.  I DID search. 
I'm looking at a non audio application which (to me) looks just like, balanced line with phantom power.  So, just for comparison, how far can you push phantom power to run a condenser mic, and receive the mic signal at the desk?
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g'bye, Dick Rees

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Re: How long can a mic signal travel.
« Reply #1 on: May 18, 2011, 01:28:04 pm »

Sorry.  I DID search. 
I'm looking at a non audio application which (to me) looks just like, balanced line with phantom power.  So, just for comparison, how far can you push phantom power to run a condenser mic, and receive the mic signal at the desk?

So your question is actually "how far can you push phantom power?".  You can use an online calculator such as:

http://www.nooutage.com/vdrop.htm

You'll have to know exactly how little power you need at the mic to figure it out.  If you have phantom power at the mic (either a battery or stand-alone power unit) you can eliminate that part of the equation. 

Otherwise, you can theoretically run for ridiculous distances with good balanced cable.  Phantom power and signal strength are entirely different issues.

And it's how far (distance), not how long (time).  Reminds me of the old Sven and Ole story:

Sven:  "Let's cut down that flagpole and find out how high it is."

Ole:  "Don't be ridiculous.  We want to find out how tall it is, not how long."
« Last Edit: May 18, 2011, 01:31:35 pm by dick rees »
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John Livings

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Re: How long can a mic signal travel.
« Reply #2 on: May 18, 2011, 04:02:27 pm »


[Otherwise, you can theoretically run for ridiculous distances with good balanced cable.  Phantom power and signal strength are entirely different issues.]

We routinely run Condenser (SM-58) and Dynamic (EV RE410) Mics over 150' Feet, Without issues. (I haven't gone longer as we have no need to.)

I have shot Video between 500-1,000 feet using wireless with OK results.

Regards,  John

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David Parker

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Re: How long can a mic signal travel.
« Reply #3 on: May 18, 2011, 07:40:00 pm »

Sorry.  I DID search. 
I'm looking at a non audio application which (to me) looks just like, balanced line with phantom power.  So, just for comparison, how far can you push phantom power to run a condenser mic, and receive the mic signal at the desk?
300' snakes are not uncommon, add to that a 50' mic cable between the snake and the mic.
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John Roberts {JR}

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Re: How long can a mic signal travel.
« Reply #4 on: May 18, 2011, 07:56:54 pm »

The issue for long distance is not the phantom power, but source impedance of the mic and the capacitance of a few thousand feet of cable. In the film industry, before wireless mics became so cheap, they used special really low Z mics (50 ohms IIRC).

It seems this has been discussed before several times.

There is no simple distance answer to your question where the mic will stop working, but it will degrade gradually with distance.

JR
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Geoff Doane

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Re: How long can a mic signal travel.
« Reply #5 on: May 18, 2011, 08:48:44 pm »

Sorry.  I DID search. 
I'm looking at a non audio application which (to me) looks just like, balanced line with phantom power.  So, just for comparison, how far can you push phantom power to run a condenser mic, and receive the mic signal at the desk?

OK, so maybe if it's a non-audio application, you don't have to worry about cable capacitance.  If all you care about is the DC characteristics of the cable, then you want to keep the cable short enough that its resistance is not significant compared to the phantom power series resistors (6.8 k).

What is "significant"?  Depends on the application.  Maybe 10%.  Maybe 1%.  If it was 1% (I doubt it), then each conductor has to be less than 68 ohms.  Different wire sizes have different resistances, but Belden 8451, 22 ga., is often considered a benchmark.

http://www.belden.com/techdatas/metric/8451.pdf

Scroll way down to the bottom, and you'll see that 8451 has a DC resistance of roughly 47 ohms/km.  So if the 1% assumption holds true, you can run about a mile of it.  10 miles, if the 10% assumption applies.

I don't think it will be a problem.

GTD
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Mac Kerr

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Re: How long can a mic signal travel.
« Reply #6 on: May 18, 2011, 08:53:46 pm »

Sorry.  I DID search. 
I'm looking at a non audio application which (to me) looks just like, balanced line with phantom power.  So, just for comparison, how far can you push phantom power to run a condenser mic, and receive the mic signal at the desk?

You say it "looks just like" balanced line with phantom power, but what is it really? I have run balanced line level as much as 3000' with no ill effects. Mic level may be less successful if all that cable causes increased susceptibility to induced noise that then gets amplified by a mic preamp. Phantom power may be a problem if it requires high current over long small cables. Guidance on how long your cable can be would be a lot better with a better description of what you are really talking about.

Mac
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Tim McCulloch

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Re: How long can a mic signal travel.
« Reply #7 on: May 19, 2011, 07:36:38 am »

You say it "looks just like" balanced line with phantom power, but what is it really? I have run balanced line level as much as 3000' with no ill effects. Mic level may be less successful if all that cable causes increased susceptibility to induced noise that then gets amplified by a mic preamp. Phantom power may be a problem if it requires high current over long small cables. Guidance on how long your cable can be would be a lot better with a better description of what you are really talking about.

Mac

+1

Just tell us what you're doing, rather than what you think it "looks like."
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James A. Griffin

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Re: How long can a mic signal travel.
« Reply #8 on: May 19, 2011, 01:03:15 pm »


We routinely run Condenser (SM-58) and Dynamic (EV RE410) Mics over 150' Feet


Huh???
« Last Edit: May 19, 2011, 01:04:58 pm by James A. Griffin »
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Re: How long can a mic signal travel.
« Reply #8 on: May 19, 2011, 01:03:15 pm »


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