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Author Topic: DMX over mic cables  (Read 7109 times)

Lyle Williams

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Re: DMX over mic cables
« Reply #20 on: October 02, 2015, 05:33:42 pm »



So why are so many of the fixtures and desks built deliberately to be non-compliant with the standard?  Because people want to use their existing mic cables, and because - up to a point - these mic cables work.

My test was just about gaining an intuitive feel for where the limit was for DMX on mic cable. 

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Rob Spence

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Re: DMX over mic cables
« Reply #21 on: October 02, 2015, 10:19:45 pm »


So why are so many of the fixtures and desks built deliberately to be non-compliant with the standard?  Because people want to use their existing mic cables, and because - up to a point - these mic cables work.

My test was just about gaining an intuitive feel for where the limit was for DMX on mic cable.

I would say they can use the same connectors to build or repair the cables.


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Scott Wagner

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Re: DMX over mic cables
« Reply #22 on: October 03, 2015, 01:10:56 am »

I would say they can use the same connectors to build or repair the cables.
Ding! Ding! We have a winner.
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Scott Wagner
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Scott Hofmann

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Re: DMX over mic cables
« Reply #23 on: October 03, 2015, 09:01:43 am »


So why are so many of the fixtures and desks built deliberately to be non-compliant with the standard?  Because people want to use their existing mic cables, and because - up to a point - these mic cables work.

My test was just about gaining an intuitive feel for where the limit was for DMX on mic cable.

OK, I can't stay silent any more.
If you want something to validate your opinion, here's a rant on DMX versus mic cable from the Cheaplights.com website. Consider the source.

A Simple Guide To DMX CABLES...
SECTION 1: INTRODUCTION
Let's talk about DMX cables... I recently received and email from a blog monitor that said... "There are MICROPHONE cables and there are DMX cables and one can NOT be used for the other". That's a very strong statement. Very "Black and White". Unfortunately, it's also very untrue. That statement would be like saying that Chevy's are for taking your kids to school and Ferrari's are for racing and one can not be used for the other. I have seen many people race Chevy's successfully and I have also seen a few Ferrari's in the school pick up lanes. I don't know exactly why people make those black and white statements about DMX cables. Perhaps they merely lack real world experience in the field.
SECTION 2: REAL WORLD EXPERIENCE
If they had real world experience, they would know that there were companies like NSI making digitally controlled lighting boards and dimmer packs with signals carried thru 3 pin XLR cables long before the term DMX was ever heard of here in America. (NSI calls their proprietary signal MICROPLEX and they still use it today). What do you think those digital signals were carried thru back before the late 90's when DMX was introduced to the commercial market here in America? MICROPHONE CABLES. That's all we had back then, that's what was used and that's what worked for years.
SECTION 3: IT's JUST A NAME
Perhaps some cables marked "DMX Cable" might perform better than some cables marked "MICROPHONE Cable", but it can also be proven that some mid to high grade MIC cables work better than some DMX cables and if you and your audience can't tell the difference, who cares? What does matter is which pins the wires are connected to on the 3 pin XLR plug. At High Energy Lighting (CheapLights.com), we currently buy "MIC" cables and "DMX" cables from over 22 different suppliers. Regardless of how they are marked, we test samples from each different "MIC" and "DMX" cable model to make sure they work in a DMX chain before we ever offer them to our customers.
SECTION 4: THE FACTS
Here's an interesting fact... In the ten to fifteen years that we have been selling cables for transmitting digital signals for light processors, we have never had any cables returned by customers saying they didn't work as a DMX cable, unless the cable actually had a physical defect, such as a wire not connected to the plug or a cut in the wire. That's a great statement to be able to make!

 Here's a few more interesting facts... 1. "DMX" was created in 1986, but not widely used or known. At that time, the popular method for transmitting signal to dimmer packs was zero to ten volts. 2. "DMX" was revised in a major way and started gaining recognition in 1990. (But not in America). 3. The first DMX lighting controllers were displayed at the American LDI Lighting convention in 1999 by LitePuter. 4. "DMX" was introduced as the "Standard" digital signal for the World Wide lighting industry in 2000.

If you feel validated now, can we stop talking about this because obviously no one is going to change your mind.
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Scott Hofmann

RyanWilliams

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Re: DMX over mic cables
« Reply #24 on: October 03, 2015, 12:57:27 pm »

OK, I can't stay silent any more.
If you want something to validate your opinion, here's a rant on DMX versus mic cable from the Cheaplights.com website. Consider the source.

A Simple Guide To DMX CABLES...
SECTION 1: INTRODUCTION
Let's talk about DMX cables... I recently received and email from a blog monitor that said... "There are MICROPHONE cables and there are DMX cables and one can NOT be used for the other". That's a very strong statement. Very "Black and White". Unfortunately, it's also very untrue. That statement would be like saying that Chevy's are for taking your kids to school and Ferrari's are for racing and one can not be used for the other. I have seen many people race Chevy's successfully and I have also seen a few Ferrari's in the school pick up lanes. I don't know exactly why people make those black and white statements about DMX cables. Perhaps they merely lack real world experience in the field.
SECTION 2: REAL WORLD EXPERIENCE
If they had real world experience, they would know that there were companies like NSI making digitally controlled lighting boards and dimmer packs with signals carried thru 3 pin XLR cables long before the term DMX was ever heard of here in America. (NSI calls their proprietary signal MICROPLEX and they still use it today). What do you think those digital signals were carried thru back before the late 90's when DMX was introduced to the commercial market here in America? MICROPHONE CABLES. That's all we had back then, that's what was used and that's what worked for years.
SECTION 3: IT's JUST A NAME
Perhaps some cables marked "DMX Cable" might perform better than some cables marked "MICROPHONE Cable", but it can also be proven that some mid to high grade MIC cables work better than some DMX cables and if you and your audience can't tell the difference, who cares? What does matter is which pins the wires are connected to on the 3 pin XLR plug. At High Energy Lighting (CheapLights.com), we currently buy "MIC" cables and "DMX" cables from over 22 different suppliers. Regardless of how they are marked, we test samples from each different "MIC" and "DMX" cable model to make sure they work in a DMX chain before we ever offer them to our customers.
SECTION 4: THE FACTS
Here's an interesting fact... In the ten to fifteen years that we have been selling cables for transmitting digital signals for light processors, we have never had any cables returned by customers saying they didn't work as a DMX cable, unless the cable actually had a physical defect, such as a wire not connected to the plug or a cut in the wire. That's a great statement to be able to make!

 Here's a few more interesting facts... 1. "DMX" was created in 1986, but not widely used or known. At that time, the popular method for transmitting signal to dimmer packs was zero to ten volts. 2. "DMX" was revised in a major way and started gaining recognition in 1990. (But not in America). 3. The first DMX lighting controllers were displayed at the American LDI Lighting convention in 1999 by LitePuter. 4. "DMX" was introduced as the "Standard" digital signal for the World Wide lighting industry in 2000.

If you feel validated now, can we stop talking about this because obviously no one is going to change your mind.

This “Guide” is junk.
Section 1
While yes you can, and we all have run DMX through a mic cable it isn’t a best practice.  DMX is RS-485 serial data.  RS-485 is balanced like audio and by design is very robust.  It was originally designed for process control in factories.  It is specified to go over twisted pair.  Microphone cables may or may not have the correct twist.  The fact that it works is a testament to it’s robustness, not permission to do so.  Like I mentioned, we have all done it…We have all had a dimmer or intelligent light that has gone “wonky” or ghosted.  Ever wonder why?
Section 2  Real Real world experience
Microplex is not a digital signal.  It is a multiplexed 0 to 10V analog signal.  It’s not even a balanced signal, and it was designed to be able to use microphone cables.  DMX by the USITT specification is supposed to be on 5 pin cables not 3 pin cables.  When the low end companies like American DJ, Chauvet etc…  got involved they started using 3 pin cables and calling it DMX-512 which is a clear violation of the USITT DMX-512 standard.  A lot of the reason the USITT standard was for 5 pin cables was to prevent people from doing exactly what you are doing and causing poor performance resulting in people thinking the protocol was junk.  Anyone who works in Theatre is accustomed to seeing DMX on the 5 pin cables.  Most of us have adaptors in our bags.  The 3 pin variance is so bad that within martin’s line they have some devices that reverse the polarity of the pins requiring one of the ends to have pins 2 and 3 swapped.
DMX is supposed to be a balanced twisted pair 120Ohm cable.  A much closer cable than microphone is Ethernet which is 100Ohm twisted pair.  It’s much cheaper and can run 4 DMX universes in one cable…Although I wouldn’t.
Section 3 It’s just a name…
Is SOOW cable just a name?  Why don’t you buy some massive THHN electrical cables throw some camloks on them and drag them around and hook up your feeders with them.  How about just before the show opens, have the local electrical inspector drop by and see if you get shut down.  Why would you buy cables from 22 different manufacturers?  Have you not found one that works well yet?
Section 4 The facts
Of course you haven’t had the cables returned.  Who is going to ship a cable back that works in the sound system back?  They just absorbed that cable into the sound system, and called a competent supplier and ordered real DMX cables from there.  You never heard from that customer again.
Interesting Facts: - Checked
1.    Partly true
a.   The DMX standard was released by USITT in 1986.  However, it became popular within a few years.  It was installed in the High School Theatre that I was going to high school at in 1990.
b.   The popular method at the time for any large show was AMX-192 with some other variants like Microplex.
2.   Completely False - The boards installed at out high school in 1990 were made by Colortran.  ETC and everyone else was doing DMX at the same time too.

The bottom line here.  Remember the rule from shop class “Use the right tool for the job”  If you have purchased $100K worth of intelligent lights are you going to cheap out on a mic cable or use the correct thing?  If you are using Chinese semi-pro low end gear like American DJ, Chauvet and the like you don’t have enough skin in the game to care if you are doing things right, and you won’t know if that device malfunction was the low end device or the wrong cable. If you have a reputation and a contract riding on it you do things correctly to specification, and it works.  Are you a pro or a semi-pro?
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Keith Broughton

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Re: DMX over mic cables
« Reply #25 on: October 03, 2015, 03:28:11 pm »

Quote
Are you a pro or a semi-pro?
And that my friends is the real question here.
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Lyle Williams

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Re: DMX over mic cables
« Reply #26 on: October 03, 2015, 05:49:36 pm »

And that my friends is the real question here.

From the first post, there was no suggestion that mic cable was the "right" solution, just one that seemed to work.

Looking at the signal on a cro after 400m, the signal still looks great.  Pull the terminating resistor off the end and it looks dreadful (but it STILL works!)

Anyone who has brought a roll of gaff tape to a show has indicated some level of willingness to improvise and get the job done.  I was just trying to put some perspective on short on-stage DMX runs on mic cable.  Not the "right thing", but not nearly as dodgey as the mythology suggests.
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Lyle Williams

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Re: DMX over mic cables
« Reply #27 on: October 03, 2015, 06:29:40 pm »

None of this necessarily makes DMX-on-Mic an acceptable solution for your customers. 

A solution customers have confidence in needs to both work, and also not violate any techno-religious, artistic, etc opinions they hold.  Across a whole spectrum of cutomers.
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Keith Broughton

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Re: DMX over mic cables
« Reply #28 on: October 04, 2015, 07:11:45 am »

And that my friends is the real question here.
Let me expand a bit on this point.
If you are a professional company in the biz, you are likely to use the cable that is specified for DMX applications as you want to maintain your reputation to your customers. You also want to make sure the top tier equipment you invested in will work properly.
If you are semi-pro ( that's not a negative thing) you have less to loose and can get away with using mic cable on the cheap "off shore" fixtures and , for the most part, it will work and your customers will be happy.
So, are you pro or semi pro?
 I would say that the people who have responded with the "use the right cable" have been doing this for a long time and have bite marks on their ass from times they thought they could get away with the "so far it has worked" approach.
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Scott Holtzman

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Re: DMX over mic cables
« Reply #29 on: October 04, 2015, 08:33:34 am »

I think a good take away is if you are going to take the risk use a terminator.

Also as I don't like the term semi pro,  how about pro serving undeserved low end of market?

The funny thing is that cables are such a small amount of the expense get the right ones. 

I learned the hard way and bought cheap dmx cables.  while the impedance may have been right the quality of construction caused more failures than using mic cable ever would.





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Re: DMX over mic cables
« Reply #29 on: October 04, 2015, 08:33:34 am »


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