[matthew_ob]

hi there,

My school drama department is putting on a production of "Little Shop of Horrors" and the sound operator has left two sends in the multicore for me to use for DMX, the issue is that I require three and the sound technician cannot use any less than the amount he has allocated left for me. So I thought it was no "biggy" but however our school doesn't have enough DMX cable to reach the third set of fixtures. But I have two very long audio cables that would do the trick. I know and have read the arguments about how you shouldn't use XLR audio for DMX but do you think I could get away with it for two performances on subsequent days after each other?

Thanks For Your Help,

Matthew

[Mushypeas]

Depends on how sensitive the fixtures' controllers are to changes in the DMX signal. What type of fixtures are you controlling?

[DeepSpacePenguin]

There's one way to find out!

[IRW]

 matthew_ob, on 16 May 2012 - 08:47 PM, said:

hi there,

My school drama department is putting on a production of "Little Shop of Horrors" and the sound operator has left two sends in the multicore for me to use for DMX, the issue is that I require three and the sound technician cannot use any less than the amount he has allocated left for me. So I thought it was no "biggy" but however our school doesn't have enough DMX cable to reach the third set of fixtures. But I have two very long audio cables that would do the trick. I know and have read the arguments about how you shouldn't use XLR audio for DMX but do you think I could get away with it for two performances on subsequent days after each other?

Thanks For Your Help,

Matthew

Er..What sort of cable is the multicore...?

As ever (with all three lines), it depends...you might be fine, you might not!

Ian

[pritch]

Leaving whether or not it's a good idea to use audio cable (and a multi) - why do you need three DMX lines in the multi? Unless you're using more than one universe (which seems overkill for most school productions), then surely you'd be having one run from the control position, and daisy chaining your fixtures?

[timd]

Given that you're already happy sending two universes down an audio multicore, I don't know why you're getting hung up over using an audio cable for a third.

[Pete McCrea]

'Best Practice' would be to use 110 Ohm DMX spec cable, through out - it isn't a 'legal' requirement that will mean you have the police knocking on the door if you don't use DMX cable.

In my limited lampy experience, and for things like this, using mic cable will work 99% of the time. One company I used to work for only ever used Mic cable - they didn't posses any DMX cable other than one 100m drum of the stuff. So often you'd end up using the sound multicore, then standard XLR to link the fixtures. And it worked, so I wouldn't stress it too much.

[Tris]

If there is 3 feeds to send then presumably this must be coming out of a DMX splitter?

Can you not just send one feed and put the DMX splitter at the other end?

[TomG]

 Tris, on 16 May 2012 - 09:13 PM, said:

If there is 3 feeds to send then presumably this must be coming out of a DMX splitter?

Can you not just send one feed and put the DMX splitter at the other end?

Not necessarily, may be using 3 separate universes of DMX from the desk, if that case would need 3 lines to the stage.

3 lines may seem like overkill but its easily done, even if there not used to capacity but for ease of wiring / programming. If there aren't enough lines to the stage then extra daisy chaining may be required or a DMX splitter, all dependant on the number of fixtures and the spare channel capacity per line...

[dosxuk]

Get a bit of cat 5 and make / buy some adaptors to suitable XLRs. I'd imagine you IT department has several part boxes of it sat in a cupboard somewhere. With the right bits, you could easily send all 3 of your universes down a single bit of DMX compliant cable this way.

[LXbydesign]

Or just repatch stuff on the desk / fixtures adressing so that you only need 2 universe's.

Unless your using 3 different control systems, each seperatly responsible for a part of the rig, I really cant see that for a school show (no disrespect to a school) you need 3 universe.

At the most, I only ever use 2 at the Academy. One for 'everything' and the other for pixel mapping.

The 'everything' line goes into a splitter - which then feeds of seperate lines to the dimmers, movers and strobe / haze / smoke etc. That all runs from the main desk.

The 2nd line from the MacPro running MagicQ runs all the LED pars / batterns.

[CharlieH]

 Mushypeas, on 16 May 2012 - 08:55 PM, said:

Depends on how sensitive the fixtures' controllers are to changes in the DMX signal. What type of fixtures are you controlling?

One of my latest shows had an interesting DMX issue. I plugged the movers directly into the desk to test them and got a DMX glitch requiring a terminator. However when they were rigged and had a load of LED Pars and hazer and generics and strobes etc connected inline then it all worked fine without a terminator. I kept it to hand just incase but it wasn't needed. I can only guess that one of the fixtures further 'downstream' had some sort of built in auto termination thing

[paulears]

If you had a problem with a short connection, then the fixture may have an issue with line impedance - so if this was cured with the terminator, knowing the 'sensitivity' of the unit, I'd have stuck the terminator in the end and left it - for safety!

[CharlieH]

 paulears, on 17 May 2012 - 09:11 AM, said:

If you had a problem with a short connection, then the fixture may have an issue with line impedance - so if this was cured with the terminator, knowing the 'sensitivity' of the unit, I'd have stuck the terminator in the end and left it - for safety!

I would have done except the line got split 3 ways and I didn't have 2 more terminators (or the time to make 2 more). So I was going to wait and see which DMX stream had problems and stick it in there.

[matthew_ob]

 pritch, on 16 May 2012 - 09:02 PM, said:

Leaving whether or not it's a good idea to use audio cable (and a multi) - why do you need three DMX lines in the multi? Unless you're using more than one universe (which seems overkill for most school productions), then surely you'd be having one run from the control position, and daisy chaining your fixtures?

There are four different control desks as we are using DMX from a Zero 88 Fat frog and analogue DIN from another. Also there is a set of two DMX dimmers and I could patch them in but our desk is out of channel faders (I have also checked that even though the fat frog has two DMX outputs it only has one universe) because the stage is not where it is being performed its in a nearby church, so another DMX controller is being used for them. Also another controller is being used for a pair of Chromaflood RGB's (There is no fixture profile for them on the fat frog or I would have patched them). I don't want to wipe the patch in the desk that has been set up for the stage at school as it wouldn't be worth the hassle to go back to school and have to re patch the whole thing again. The multicore was being used as an easy way to get the DMX signal over long distance as where it is being controlled from is at the back and the dimmers and fixtures are at the stage and as I said in the original post we don't have enough DMX to just daisy chain.

 Mushypeas, on 16 May 2012 - 08:55 PM, said:

Depends on how sensitive the fixtures' controllers are to changes in the DMX signal. What type of fixtures are you controlling?

We will be using four Martin Mac 250's

This post has been edited by matthew_ob: 17 May 2012 - 09:45 AM