# Saturday at NAMM - Live Blog

#### dvsDave

##### Benevolent Dictator
Senior Team
CB Mods
Fight Leukemia
Good Morning! @gafftaper and I will be walking the floor again today and tonight we will be attending the Technical Excellence and Creativity Awards (TEC Awards) as a sponsor. This is the premiere event at NAMM and it's a veritable who's who. We loved the TEC Awards last year and are really looking forward to tonight's event.

SKB Cases has a new version of their Studio Flyer with a 4U rack space. Going to check it out today.

Gator cases has a series called Gator Frameworks and they have some really cool accessories for mic stands that I want to check out.

Need to stop by SoundTools and see what new toys Dave Rat has been coming out with.

Last night we got to meet up with Neutrik and got to see their new TOP product line. Very cool. Will be uploading pictures later. We were also told there is a very interesting story we need to track down about DMX cable and why it's made the way it is. So, we are going to follow up on that today.

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#### BillConnerFASTC

##### Well-Known Member
Very cool - Control Booth right between QSC and Wells Fargo. What do you have to do to be next to Amazon, and how cool would that be!

#### dvsDave

##### Benevolent Dictator
Senior Team
CB Mods
Fight Leukemia
From my friend who's a rep at Sennheiser.

Security professional 8:09 AM Starbucks Marriott Anaheim. You better think twice bout starting some mess up in here cause this MF will go John Wick on your sorry soul with a Venti sized whoopin...

#### gafftaper

##### Senior Team
Senior Team
Fight Leukemia
Gator Cases has their "Frameworks" products on display. Several really nice products to check out to accessorize your mic stands.

There's a great little clamp on mini boom for hanging a second mic down below for a guitar or whatever.

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Senior Team
Fight Leukemia

#### What Rigger?

##### I'm so fly....I Neverland.
From my friend who's a rep at Sennheiser.

Security professional 8:09 AM Starbucks Marriott Anaheim. You better think twice bout starting some mess up in here cause this MF will go John Wick on your sorry soul with a Venti sized whoopin...

View attachment 17388
Dude may be big, but he doesn't have cauliflower ears, so I like my chances.

RonHebbard

#### Michael K

##### Well-Known Member
Thanks for all the thoughts and info on NAMM this year!

We were also told there is a very interesting story we need to track down about DMX cable and why it's made the way it is. So, we are going to follow up on that today.
Any follow up on this? You've peeked my interest!

#### dvsDave

##### Benevolent Dictator
Senior Team
CB Mods
Fight Leukemia
Thanks for all the thoughts and info on NAMM this year!

Any follow up on this? You've peeked my interest!
Yes, I need to compare notes with @gafftaper, but we managed to track down the person who had the story.

#### gafftaper

##### Senior Team
Senior Team
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We were told there was a great story about why there are two twisted pairs in the DMX specification. We tracked down the person. We were told that a manufacturer started using the extra lines to send power down the DMX cable, so they were stuck with two twisted pairs in the standard. From the setup, I was expecting something different and left unsure if I was told the correct story. Perhaps @STEVETERRY can enlighten us as to if there is another story about the reason for the two twisted pairs in the DMX standard or not.

RonHebbard

#### STEVETERRY

##### Well-Known Member
We were told there was a great story about why there are two twisted pairs in the DMX specification. We tracked down the person. We were told that a manufacturer started using the extra lines to send power down the DMX cable, so they were stuck with two twisted pairs in the standard. From the setup, I was expecting something different and left unsure if I was told the correct story. Perhaps @STEVETERRY can enlighten us as to if there is another story about the reason for the two twisted pairs in the DMX standard or not.
It's a pretty mundane story:

1. DMX512 got the 5-pin XLR to prevent mic cable from being used inadvertently. Also, Colortran used the XLR-5. Colortran protocol was a precursor to DMX512 that used EIA-485 serial at 153.6 kbps.
2. There was no common use for pins 4 and 5, so they got designated as a spare data link in the original DMX512 standard. EIA-485 rules were implied for this spare link, but not specifically called out.
3. Entertainment Technology and Rosco began using the spare pair as a back channel for IPS distributed dimmers. Other people used 4 &5 for a second DMX512 universe.
4. Some European manufacturers began using pins 4 and 5 for supply of 24 Vdc. This violated the EIA-485 common mode voltage limits and generally blew up EIA-485 transceivers that might get connected to pins 4 and 5.
5. BIG outcry from manufacturers using pins 4 & 5 for an EIA-485 link, who did not appreciate the smoke.
6. ESTA issued a warning about 24V on pins 4 & 5 of some gear.
7. When the standard was revised, the acceptable use of pins 4 & 5 was tightened to EIA-485 electrical limits.
8. It all became somewhat moot with the appearance and wide adoption of ESTA/ANSI E1.20 RDM, which uses the main data link on pins 2 & 3 in a bidirectional mode for command and control.

And there you have it.......

ST

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#### derekleffew

##### Resident Curmudgeon
Senior Team
4. Some European manufacturers began using pins 4 and 5 for supply of 24 Vdc. This violated the EIA-485 common mode voltage limits and generally blew up EIA-485 transceivers that might get connected to pins 4 and 5.

http://www.pin4power.com/

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We were told there was a great story about why there are two twisted pairs in the DMX specification. We tracked down the person. We were told that a manufacturer started using the extra lines to send power down the DMX cable, so they were stuck with two twisted pairs in the standard.
Story doesn't hold up because:
1. Why would anyone think sending 24V over 22g or 24g wires was a good idea?
2. Twisted pair is not required and does nothing for voltage.

In 1979 with the introduction of the CD-80 protocol (which later became AMX192) the phrase "Control of 192 dimmers over two twisted pair" became ubiquitous. Add a shield, switch to 5pin, and control 512 dimmers.

#### gafftaper

##### Senior Team
Senior Team
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Thanks @STEVETERRY .

The bigger conversation that came out of this was should we keep producing cables to the spec with the two twisted pairs or not? We talked with two experts on the topic. Fred Morgenstern (Neutrik) talked about how much copper we are wasting and how much more expensive DMX cable is because of the standard. While it would be great to produce a cheaper cable that doesn't meet the spec and increase sales as a result. Neutrik works hard to be the code compliance experts, so it's just not something they can do. Meanwhile Colin Waters (TMB) talked about how the Europeans gave up on the unnecessary extra wire long ago. It's only in America that we are still set on fully meeting the code. Does it make a difference? Technically, Yes. How big of a difference? The difference is measurable, but if you follow good practices for the rest of the system, you will probably never see a problem. On the other hand, as we are fond of saying around here, "DMX is very forgiving and it works, until it suddenly doesn't". When you reach a point that it doesn't work, you will wish you had purchased all high quality components that do fully meet the spec.

Do you want to take the risk of saving a few bucks on cable but someday having a lighting problem as a result? I sure don't. Give me the extra copper.

#### STEVETERRY

##### Well-Known Member

http://www.pin4power.com/

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Story doesn't hold up because:
1. Why would anyone think sending 24V over 22g or 24g wires was a good idea?
2. Twisted pair is not required and does nothing for voltage.

In 1979 with the introduction of the CD-80 protocol (which later became AMX192) the phrase "Control of 192 dimmers over two twisted pair" became ubiquitous. Add a shield, switch to 5pin, and control 512 dimmers.
The original story holds up because it is precisely what happened. Manufacturers of certain dimmer or relay panels wanted a cheap way to power simple controllers without adding a wall-wart or other power supply at the controller. The controller only needed a few mA, so the gauge was not an issue. The fact that it was a twisted pair was incidental because the conductors were present in the cable, not as a requirement for the 24V power. The only problem was non-compliance with EIA-485.

The pin4Power guys seem to have the same idea, but are within the 485 voltage limits.

ST

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RickR

#### derekleffew

##### Resident Curmudgeon
Senior Team
Can you even get cable with two pair - 1 twisted and 1 not twisted?
Like I said, I don't know and don't care if the "power pair" is twisted. But IF I were going to use it for power,
Thanks, Dave, for that very thorough explanation. Thanks also for the cool picture, from the Manual cited above:

DL's Photobucket
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...Does it make a difference? Technically, Yes. How big of a difference? The difference is measurable, but if you follow good practices for the rest of the system, you will probably never see a problem. On the other hand, as we are fond of saying around here, "DMX is very forgiving and it works, until it suddenly doesn't". When you reach a point that it doesn't work, you will wish you had purchased all high quality components that do fully meet the spec.

Do you want to take the risk of saving a few bucks on cable but someday having a lighting problem as a result? I sure don't. Give me the extra copper.
Please explain how using single pair cable and not wiring pins4&5 will ever cause my DMX to "break." I can only think of three (highly unlikely) instances:
1. I require the talkback feature of long-defunct Entertainment Technology products. Yeah, right.
2. I'm using a HogII rigger's remote. Not in the last fourteen years.
3. I'm using an early Avolites Pearl and/or have cheater break-in/-outs to access a 2nd universe. As a standard practice, I've already long run a second cable as a spare, marked with yellow tape.

JohnD

#### STEVETERRY

##### Well-Known Member
Like I said, I don't know and don't care if the "power pair" is twisted. But IF I were going to use it for power,

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Please explain how using single pair cable and not wiring pins4&5 will ever cause my DMX to "break." I can only think of three (highly unlikely) instances:
1. I require the talkback feature of long-defunct Entertainment Technology products. Yeah, right.
2. I'm using a HogII rigger's remote. Not in the last fourteen years.
3. I'm using an early Avolites Pearl and/or have cheater break-in/-outs to access a 2nd universe. As a standard practice, I've already long run a second cable as a spare, marked with yellow tape.
I agree with Derek on all three points. However, it would be nice to know via obvious marking that pins 4 & 5 are NC.

ST