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I need to buy a switcher to take multiple VGA sources into my Davis projector (single DB15HD input). I have a well priced 6 in 1 out Kramer switch available which has a bandwidth of 180MHZ and was wondering if this is enough? My sources will be PC (Geforce2) at XGA, a Dreamcast console (using VGA breakout box), a HDTV set top box, a satellite tv set top box, and possible a laptop from time to time.

Can anyone comment, Im striving for that champagne on a beer budget again http://www.avsforum.com/ubb/smile.gif
 

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350 Mhz is the number that is often used. 350 Mhz gives you plenty of head room for higher scan rates and higher resolutions.


For example, a line doubled 1080i signal would require


1920 X 1080 X 60 = 124 Mhz dot clock


To correctly pass this signal, you should roughly double the dot clock frequency for the bandwidth of the switching equipment. That means about 250 Mhz.


Many computer displays can achieve a combination of resolutions and refresh rates that will easily exceed a dot clock of 124Mhz, so having a little extra bandwidth gives you some room to grow.
 

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JoeFloyd,


Is there a bandwidth limit on cables as well. I added a VGA extension cable to an existing 25 ft VGA cable and the input from my laptop would no longer sync with the projector. I'm hoping adding a quality powered switcher such as http://www.altinex.com/Solutions/switchers/da1916sx.htm will eliminate the problem. But am not sure on the type VGA extension cable I should use.


Thanks for the info.


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Mark II
 

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Does anyone know how well these switchers work with a DILA? I currently run 3 video cables to my DILA (VGA, RGBHV and S-VHS). Since my cable run is going to be around 40 feet, I'm going to replace my current cable with high quality cables like bettercable. But I'm thinking that it may be better to put the money for 3 cables into one cable plus a switcher.


Currently, my HDTV STB uses the RGBHV input and always synchs to the HDTV input source, while my computer uses the VGA and synchs to the computer3 input source.


If I use one cable, plus a switch would I feed everything into the RGBHV input to the projector? Would this be an optimum setup or would I be losing something in the process?


Anybody have any ideas?


Thanks,

Mark


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Calibrated G11 DILA, 7' 16x9 Greyhawk, Radeon HTPC, Panamorph (soon), DTC-100, AccessDTV, Lexicon MC-1+, B&W Nautilus 804's, HTM1, SCM1s
 

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The main difference between different switchers are buffered vs. unbuffered.


Buffered switchers are preferred since they provide electronic isolation along the signal pathway. This will result in a more stable picture with less ghosting, or other forms of signal degradation. These are also the most expensive type of switcher.


Full mechanical switchers are by definition unbuffered, but that doesn't mean that they cannot provide very good image quality. The design of the mechanical switch components has to be carefully performed to avoid all the common forms of signal degradation. While there is a science to these things, there is still a lot of art to perfecting all the details.


Cables and connectors have a lot a variability. The cables and connectors are designed with a given signal bandwidth in mind, but since they are analog devices there is a lot of variability from one cable to the next as well as from manufacture to manufacture. The best choice when it comes to cables is to find a review from someone with a similar application and see what they had to say. BetterCables is often given high praise for the quality of their products, but DigitalConnection also sells VGA cables that should be of high quality.


With longer cable runs it difficult to produce cables that will not be a source of some image degradation and buffered switchers or distribution amplifiers can be very helpful for these situations. Again, the best advice is to search for a product review that seems to be similar to your application.
 
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