It does go back years now doesn’t it. You still the best on electrics I trust and it’s good to have your advice, but also hope to open this up to others willing to take on this concept question.
This concern about equal lengths is indeed once inner/outer core conductors my concern in should it be that someone plugs the Clear Com into the wrong circuit. However you might have misunderstood the tying together of pairs.
Let’s say for a universal system, all cables are wired on a 37pin multi-cable, 1-3 pins on it representing pins 1-3 for DMX circuit one, 4-6 pins 1-3 for DMX circuit two, 7-9 pins circuit three and so on. In other words, in doing 37 pin, the first eight pairs of cable are all in order of pins 1-3 as the repeated action. This way it does not matter how many channels of snake is once plugged into another snake, from six pair to 16 pair, or anywhere from 6 pair once plugged into a 16 pair snake will still convey at least the six circuit, eight or six semi-true DMX and two non but XLR.
After this and starting at pin 25, I start doing the second pair of doing true DMX as repeated thru pin 36. Pins 25 thru 26 are circuit 1 pins 4 &5, pins 27 and 28 are 4&5 of circuit two and so on. The only thing shared in tying together these circuits to be as if one are the shield wires that for say in making pairs #1 and #9 have both wires tied into pin #1. In other words, in this instance the drain of the outer wrap circuit #1 is tied into another outer conductor, but from #3-6 in having inner core conductors of a shorter length, the drain wires are tied together in terminating in the same place.
For say circuits 1thru 2, given conductors - drain wires are the same length, as a theory given Clear Com both follows the path of least resistance and the secondary pair in causing this grounding loop - even if by way of NEC for duplicate cables is that if two are the same length or at least within reason the same length, it should not matter. On the other hand, it could given it’s more or less a data signal. This than two part than in question, given someone plugged into circuit 1 or 2 in that both are in all ways outer core wrap and the same length for the shared drain wire, would this cause a grounding loop? Given two drain wires even if terminated on both ends to the same pin, would they work more as per the NEC of same length conductors, or more by way of crapped up data? Than for pairs 3-6, given one shield is a different length as a theory, would this cause a problem even if only about 12" expected over 400'?
For DMX cable circuit #5 for instance, it would have over it’s five pins, Pair #7 going to pins in the Soco, #19 thru 21. Than for the second pair Circuit #13 by way of drain wire also going to pin #19, than pins #4 going to pin #33 and Pin #34 going to pin #5 of the DMX.
It’s sort of in order, pins 1-3 of all circuits DMX or XLR going to the first 24 pins, than the final pins 4&5 following it by way of circuit number. Pin #37 is a general ground for the snake cable which grounds the output boxes themselves inlet and output just in case. That’s the snake cable itself as terminated in 37 pin Socapex which I curse every time I get one to repair due to bad design of the plug.
Believe where we beyond this are more confused is where it comes to the output rack panels or truss snake boxes. Figure as above a plug or outlet panel mount connector that attaches to the snake. Each individual pair or conductor than say terminates into it’s appropriate place in a five pin panel mount plug or connector attached to the box. Good rugged boxes, the box doesn’t fail, nor does the 16 panel mount connectors, just the Socapex - constantly. Curse Socapex and the person that chose this plug.
In any case, the 5-Pin DMX in the box is than jumpered off to a XLR 3-pin panel mount also mounted into the box. This thus circuit’s 1-8 have both 5-pin and 3-pin outlets for them in using pins 4&5 or not. Granted circuits 7&8 don’t have a second pair tied in with them at all but they still also in doing if necessary fake DMX, have a 5-pin outlet. Outlets themselves in the output box are just tied together 3-pin and 5-pin boxes.
Circuit #8 is reversed sexed in being the designated Clear Com circuit as a universal thing. This granted FOH no doubt makes use of a lot of MM/FF adaptors in making up for two circuit Clear Com adaptors. Still 6 circuits of DMX and two for Clear Com seems to be enough for most shows beyond the large ones where larger now Wirlwind 61 pin or dual snake shows are in use.
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Topic: termination of drain wires in a snake when both DMX and Clear Com (Read 1452 times)