Here's the link to the DD factsheet: http://www.etcconnect.com/docs/docs_downloads/datashts/DimmerDoubler_vF.pdf
Here's the link to the manual: http://www.etcconnect.com/docs/docs_downloads/manuals/DimmerDoubler_User_Manual_revA.pdf
The S4 Jr is a compatable fixture type, so you need X amount of HPL550/77 lamps, and X amount of dimmer doublers.
The rest assumes you have an ETC console as well as Sensor dimmers.
Essentially what you are doing is putting a 77 volt lamp into a fixture, with one 77v fixtures on ea half of the DD 2-fer (so they work in pairs, though you don't have to load both sides of a DD), you then assign specific Sensor dimmers to run in DD mode, which has one half of the dimmers sinewave output split by the DD, the upper half to one fixture, the lower half to the 2nd fixture. You then tell the console that you are running in DD mode. It splits a universe of DMX addresses into 1-256 as DD 1-256A, with DMX addresses 257-512 as 1-256B.
77v lamps run about $17, the DD is currently available as used from 4Wall/UsedLighting.com @ $89 ea., they say they have 35 available, and as they come from a reputable source, it's a steal. It's a good idea to maybe buy extra lamp caps for ea. fixture you want to DD, so the caps used for DD will have a twistlok plug as used by the DD 2-fer. Keeping the DD 2-fers at twistlok helps prevent damage and blown lamps. Or buy adapters.
Steve B.
[edited by: Steve Bailey at 8:30 PM (GMT -6) on Thu, Mar 26 2009]
Essentially what you are doing is putting a 77 volt lamp into a fixture, with one 77v fixtures on ea half of the DD 2-fer (so they work in pairs, though you don't have to load both sides of a DD), you then assign specific Sensor dimmers to run in DD mode, which has one half of the dimmers sinewave output split by the DD, the upper half to one fixture, the lower half to the 2nd fixture.
So, I know I am necroposting, but since Steve B. mentioned it in this post I thought it would count as related. :) I've done a fair amount of work with dimmer doublers in the past, but always counting on my ME (who really knows his sh**) to be the one to really have to worry about them. So, recently I was working on another show with DD with a different ME and the idea came up that you have to load both sides of the multiplexer. I was like, I've never heard of that or have had to do it in the past. They said that they had heard if you don't have a load on both halves, they wont work properly, like they wouldn't dim all the way, or wouldn't be as bright at full, or something. I argued that I didn't think that was true because I had never seen that before and I have done shows where I only put a load on one half of the multiplexer, but I don't really have the science to back that up. Is there any truth to this? If so, why?
There is no requirement to load both branches of the dimmer doubler. Essentially half the waveform goes to either branch of the doubler; the positive half of the waveform goes to one branch, the negative half to the other. Since the Sensor rack is upstream of the doubler, it always sees the full waveform, knows where the zero crossing is, and is, for all intents and purposes, immune to the presence or absence of a load on either side (or both sides) of the doubler.
The manual says there IS a safety requirement that load connectors be installed on both branches a dimmer doubler. This might be confusing your ME. It's the same as saying you should not have exposed wires sticking out of a receptacle.
I've used dimmer doubling quiet a bit with regular S4s & S4 PARs & it works quite well. I've run both sides loaded, A or B alone & I've never had a problem. I've heard there can be some noticeable flicker on video, but have never had any videographers complain about it or even mention it; I sure couldn't see it, if it happened. Just make sure you set the D20 for DD. BTW, it's circuit independent too, so you can have one side of the D20 set for DD & the other running a regular load. The 77 volt lamps run 550 watts.
I don't use dimmer doubling much anymore because I've acquired enough D20 modules to fill out my racks.
I've used dimmer doubling quiet a bit with regular S4s & S4 PARs & it works quite well. I've run both sides loaded, A or B alone & I've never had a problem. I've heard there can be some noticeable flicker on video, but have never had any videographers complain about it or even mention it; I sure couldn't see it, if it happened. Just make sure you set the D20 for DD. BTW, it's circuit independent too, so you can have one side of the D20 set for DD & the other running a regular load. The 77 volt lamps run 550 watts.
I don't use dimmer doubling much anymore because I've acquired enough D20 modules to fill out my racks.
Thank you for your replies, but I know how dimmer doubling works on the surface, I just don't have the electrical engineering knowledge to say they are wrong. For example, I know that the multiplexer divides the wave so that the positive goes to one plug and the negative to the other and that;s why you use 77V lamps and so on, I just couldn't tell you for certain that only putting a load on one half doesn't have some funky effect on it. Like, maybe a higher voltage drop on only the positive half of the waveform would cause some abnormal behavior. I just don't know, is the point.
I don't know how to answer your question without going back to first principles and diving into a whole lot of physics and basic electrical engineering theory that just cannot be covered in a forum. I also am having a hard time proving a negative so let's turn the question around.
What sort of noise would have to manifest on the neutral in order for the waveform on one of the branches to be distorted in some way? How would that noise get there?
Or forget about dimmer doubling and try this. Given 2 properly terminated independent circuits that share a common,neutral (which happens to describe every circuit in the dimmer rack), under what circumstances would a load on the one circuit have an impact on the other?
Tell me if I'm wrong, but isn't what's going on in a DD situation more complicated than just two circuits sharing a common neutral? Or is it not and I am making this harder than it needs to be?
[edited by: Xander at 1:44 PM (GMT -6) on Sat, Mar 12 2011]
You are making it more complicated than it needs to be. The only magic going on is that half the waveform is going through one lamp and the other half going to the other.
. Given 2 properly terminated independent circuits that share a common,neutral (which happens to describe every circuit in the dimmer rack),
Perhaps a clarification for this. Branch circuits do not share neutrals. All such circuits have a hot and neutral wire terminated in the rack. The 3 feed phases share a neutral (or 2 feed phases of a smaller rack wired for single phase/3 pole/4 wire).
