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Multiple DVD players sharing receiver inputs

Discussion in 'Home Theater Projects' started by Richard K.F., Oct 30, 2004.

  1. Richard K.F.

    Richard K.F. Auditioning

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    I have an Onkyo SR 701 receiver that supports only two RGB sources. Currently Ive connected a scientific Atlanta Cable box to one and a JVC DVD player to the other. I also have a SONY CX985V 400 DVD/CD disk player that I've connected to an S-Video input. It all works together just fine, but it occurred to me that the 400 disk player is extremely space efficient and doesnt cost that much more than decent quality DVD storage units. So I am thinking about getting additional units. what I've thought about doing was to interconnect multiple DVD RGB outputs using ordinary TV splitters (bridges, one for R, one for G, one for B and one for digital audio. Assuming only one DVD player is on at a time (remaining units in stand-by), it seems as though they could share a single set of receiver inputs that way. If a second DVD player was accidently turned on, i would think there would be serious interference, but I dont think any damage would occur. Was wondering if anyone has tried this kind of connection, and also would be interested to hear about alternative solutions. Thanks in advance for your inputs.
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Hi Richard. Welcome to HTF. [​IMG]

    It is a very bad idea to use "Y" splitters for your video connections.

    You will not find any "Y" splitters made for video. They are all made for audio. This is because the high-frequency video signals are very sensitive to something called "Impedence" of the cable. The signals want to see a smooth, uniform impedence along the cable path. "Y" connectors, barrel connectors, and even cheap RCA plugs really mess up the impedence.

    What you want is a video switcher. You can get inexpensive ones from Radio Shack, or some better ones that switch digital audio as well as described in this thread on Inexpensive HD Video Switching
     
  3. Richard K.F.

    Richard K.F. Auditioning

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    Hi Bob; Thanks for your input. I wasn't referring to audio bridges. My thought was that standard 75ohm TV splitters (the passive kind you would use to distribute your cable signals around your house, designed for video frequencies) would possibly do the job. My thoughts were that they would maintain the 75 ohm impedance required for the RGB and digital audio signals and be able to support the bandwidth required for these signals. I would be using them backwards (multiple video frequency sources [used one at a time] to a single output connected to the inputs of the receiver). My hope was to avoid the use of mechanical switches or relays.
    thanks again.
     
  4. Bob McElfresh

    Bob McElfresh Producer

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    So you would cut the ends off some video cables, install "F" connectors and use 3 CATV splitters...

    It might work. However the frequencies involved are not what those splitters were designed for. CATV signals are in the RF frequency range for analog or Gigahertz for digital signals. Video signals fall in-between these 2 applications.

    So... it largely depends on how the splitters work at video frequencies.

    If you are willing to do it - go for it and let us know. However: this will take the modification of 3 sets of component cables plus the cost of 3 good splitters. Even using my favorite 'cheepie' cables (AR Pro) - thats about $75-$90 worth of cables to experiment. About the price of a modest switch box.

    You CAN try CATV grade RG6 coax cable which would be a lot cheeper. But once again - the coax is built for different frequencies in mind, but it would be a lot cheeper to experiment.

    You have an interesting idea. I'd love to hear the results.
     
  5. Leo Kerr

    Leo Kerr Screenwriter

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    I think there might be a couple of other problems, I don't know this, but here's what I'm thinking:

    1. Yes, if a second unit is powered on, you will get some seriously ugly interferance.

    2. Are those passive splitters truly passive, and will they work.. 'backwards' without affecting the signal? I don't know. Interesting concept; I don't know.

    3. What sort of signal load/sink does one of the other players in the 'off' state represent? It's quite conceivable that if it is off, it may 'suck' a great deal of signal out of the one working source, and possibly deprive the monitor of enough drive signal, and/or cause other image problems.

    Of the three, #3 is the one that is my biggest concern about this sort of project.

    Leo Kerr
     
  6. Richard K.F.

    Richard K.F. Auditioning

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    Thanks again for your thoughts Bob. I will probably make my own cables if I feel confident enough to go ahead with it. Will let you know the outcome.

    hi Leo; I'm pretty sure the tv splitters are passive and bidirectional as I have cable service for both TV and Internet access and have at least two splitters between my router and the cable service interface.
    Your third point is one that has concerned me as well. I'm not familiar with what kind of drivers they use on the RGB outputs and digital audio outputs of DVD players and it is entirely possible they may offer excessive loading when unpowered, (though i expect some isolation will be provided by the splitters). My other concern is if the drivers are in the unpowered state is there any possiblity they could be susceptable to some kind of reverse voltage breakdown from the signal generated by the active unit, that could permanently damage them. My guess is that the signal levels are probably too low to cause any damage, but was hoping someone could confirm my suspicion before I actually try it.

    Thanks again to both of you for sharing your thoughts.
     
  7. Leo Kerr

    Leo Kerr Screenwriter

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    I doubt that the splitters will offer any form of isolation. The easiest (it seems) would be diodes, but then you'd loose a tremendous amount of signal through each one. And who knows (not me) what it'd do to the signal.

    I would not worry about what the signal coming into a player's output hurting the output. Not unless you're bumping it through a monster distribution amplifier.

    Instead, in addition to harming the immediate signal quality, it is possible to cause longer-term damage to the output circuitry. I don't know if this would, but here's my anecdotal experience.

    We had an industrial DVD player down in the master control room. The display was roughly 450' away, as the composite cable ran.

    Initially, it was fine. Over the course of several days, however, the signal began to degrade: overall luminance levels dropped, and the color quality began to fall. (Recognizing this, quick slap a distribution amp in line, switch to a different output, et voilá!

    (now, for reference, we've gone to always using distribution amplifiers, even when we probably don't need them... we've got an entire rack of Videotek Omniframes, chock full of video and audio DA cards... it's insane.)

    Leo Kerr

    EDIT: I realize I missed a key point here. If you try this, I believe that you will be able to test this out without likely causing any permenant harm to any of your components (except, perhaps, the decapitated cables.) Let your eyes be the judge; bad pictures are often similar to pain: nature's way of telling you to STOP!!! [​IMG]
     
  8. Richard K.F.

    Richard K.F. Auditioning

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    thanks again Leo. the degradation you described sounds like a semiconductor dying a slow death, a little scary!! I think i will try to get specs on the driver from SONY before I try it. May end up having to go for a mechanical solution after all.
     
  9. John Garcia

    John Garcia Executive Producer

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    For the digital audio, you will have to do the same thing...

    Not sure if you read your manual or not, but the Sony players can be daisy chained together with the first one in the chain controlling the subsequent players (up to 4 I think?), so what you are asking probably isn't even necessary. You shouldn't need a switch at all. A friend has a 200 disc and 400 disc hooked up this way and it works fine.
     
  10. Richard K.F.

    Richard K.F. Auditioning

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    Hi John;
    thanks for your inputs. The SONY units permit daisy chaining three units. My DVD collection is approaching 1000 which i currently store on shelving, which takes up quite a bit of space and if i start getting some decent looking shelves they will probably cost almost as much as the SONY players. So for a relatively low cost penalty i can get a lot of space efficiency using the SONYs for storage. But another 200 or so disks and i'm back to using shelves. Also have a single DVD player and cable box, so am out of RGB input on my receiver (Onkyo only has two RGB input sets). That was the reason i started down this road. I got to admit though i'm starting to get a little nervous about this scheme and may have to settle for a mechanical solution.
     
  11. Richard K.F.

    Richard K.F. Auditioning

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    Hi all; here's an update. The Sony units don't really daisy chain, they simply have three different remote control settings so you can control each of three units without affecting the others. They still each require their own inputs to the device they are connected to. i opted to use an Audio Authority four input component video and digital audio switch marketed by Smarthome Cat#7772. Its fully automatic and selects whichever device provides a signal. So far i've connected my JVC single DVD player to it and the Sony DVD player. I can connect two more Sony units to it for a total capacity of 1201 disks. It works fine, so will settle for that for the time being. i expect by the time i get up to 1200 disks more solutions will be available, so will cross that bridge when i come to it. Meanwhile thanks for you suggestions and participation and hope you all have a happy holiday season.
     
  12. Bob McElfresh

    Bob McElfresh Producer

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    That unit has gotten some very good reviews and is very popular for people who run out of inputs. Good choice.

    Happy Holidays to you as well. [​IMG]
     

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