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RGB Connectivity Question

Discussion in 'AV Receivers & Amplifiers' started by MrJubbly, Feb 11, 2002.

  1. MrJubbly

    MrJubbly
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    Hi,

    I've read some posts on these boards in the past regarding RGB connectivity between TVs and AV Amps, but if someone could answer me the following I would be most grateful:

    I have a TV with 2 RGB (in) enabled scart sockets and I am upgrading my amp to the Denon 3802 (who isn't!!!). My first question is can the RGB outputs on the Denon be used to connect to the TV? In some instances I've read not and in others I've read Yes. I understand that true RGB requires 4 cables/connects (R, G, B and Sync), and that the RGB provided on the back of the likes of the Denon the Sync is somehow incorporated (I've read a more techie explaination elsewhere I'm sure!!). Anyway what my question boils down to is can you in fact connect the Denon 3802 to a TV that has an RGB enabled Scart socket (i.e 3 phonos to Scart)? The more I think about, I guess not, but it would be nice if someone could clarify.

    One other question. If the TV were connected to the Amp over and RGB connect, would the Amp be able to switch a source to the TV that was connected to the Amp via another method (composite or S-Video)? Again, my guess is not.

    Thanks is advance for any help.

    Regards,

    MrJubbly :confused:
     
  2. ReTrO

    ReTrO
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    You can switch RGBS through the Denon by using a SCART to RGBS (phono RCAs) lead from your Digibox etc to the Denon, and an RGBS to SCARt lead from the Denon to your Tv's RGB enabled SCART. The S sync sugnal should be sent through the composite video section.

    The amp will still switch s-video or composite video through the other inputs, but these will need to be connected to different SCART inputs on your TV.
     
  3. MrJubbly

    MrJubbly
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    I thought an RGBS scart consisted of R, G, B, and and Sync cables/connects (4 leads/connects). The Denon has only 3 sockets for component connectivity. I've not yet been able to find a Scart to 3 phono, arrangement that would carry the RGB and S signal. If the connectivity I have described is truely possible, then where can I get such a lead?
    If the Amp can switch the video signal from a source connected to the Amp over, say S-Video, to the TV connected via the RGB arrangement discussed above, what is the need to connect to the TV over different inputs? Or are you saying that the Amp can cope with varying types of video input, but that the output to the TV must match a given input? i.e if S-Video comes into the Amp then the output to the TV must be likewise.

    Thanks for the help so far.

    Regards

    Mr Jubbly
     
  4. Fartpants

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    Many TVs have more than one scart, but on most only one of the scarts is RGB enabled.

    Most amps have composite and SVHS switching, some have component switching, but this is not compatable with RGB scart without an adapter inbetween.

    I use a Btech box to switch RGB sources, most gadget places stock'em I got my from beyondhifi

    Shame really coz I would like everything switched through one box
     
  5. paiger

    paiger
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    I think the video signals are carried on seperate busses to their outputs. So if you plug a DVD into the Svideo input on your Denon, that will only be output through the Svideo monitor out. To make it worthwhile you want it all on one bus really (one type of signal). For most people this is only possible with composite so it's not worth it. If you can plug all your inputs into the component ins on your amp then they should all come out the component out sockets to your TV. I'm pretty sure thats the case anyway but I am prepared to be corrected.

    Not sure where you get such cables though.

    S
     
  6. ReTrO

    ReTrO
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    MrJubbly: You can get the RGBS (4 phonos) leads from companies such as QED, Chord or IXOS (Chord and IXOS require special orders). The 4th lead carrying the 'S' Sync signal should be routed through the composite video section of the amp.

    Very few amps will do internal video transcoding, converting one type of video signal to another. Which is why you wuld still require an s-video output to your TV/monitor if you were inputting s-video to your amp.

    In theory you could send all the video signals into one SCARt input on your TV. It is unlikely that a singal SCART will support both RGBS and s-video though, and those that do will most probably need the change to be made through a menu system.

    You would find it hard to get a custom SCARt made that supported both RGBS and s-video input.
     
  7. bxd

    bxd
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    Hi,

    On a thread somewhere we had a bit of a discussion about connecting rgb thru the component video connections on a Denon amp and using the composite video socket to carry the sync signal. Someone tried this out and it does work...... but.... you may also need to send a signal which triggers the rgb on the tv.

    Therefore what you need to do is to :

    1. Get some scart to phono cables made up. These need to carry r, g, b + composite video (all grounds connected) AND something (eg a phono) to carry the trigger voltage. You use this to get rgb out of the source (dvd or sky)

    2. Connect these into the amp. (leave the trigger signal for now)

    3. Get a phono to scart cable which feeds the r,g,b+sync,+trigger signals to the tv.

    Now, I presume (and someone can correct me if I'm wrong) that it doesn't matter where the trigger voltage comes from ..... as long as the rgb sources are turned on. If you connect the trigger cable from any of the sources to the tv (i.e. bypass the amp) then that signal should be present on the tv.

    If you're trying to switch progressive signals (e.g vga with combined sync) to feed a projector then you might not need the trigger signal.

    Another possibly easier option is to get an rgb capable scart switcher and just wire things that way ..... independent of the amp.

    Brian
     
  8. MrJubbly

    MrJubbly
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    Thanks everyone for the replies so far.

    I'm begining to get my head round this slowly!

    Retro: Assuming I can get the cables and the Denon 3802. Would I be correct in saying that from the Amp to the TV I would connect the R, G, B leads to the Monitor (OUT) R, G B sockets, and the 4th composite lead to the composite socket of the Monitor (OUT). Obviously the Scart then connects to the TV. Then, for a source, such as DVD player, would I connect the Scart to the DVD player, the R, G, B leads to the DVD Component (IN) sockets, and the composite lead to the DVD (IN) composite socket?

    Is it as simple as this? I'm bit concerned about the 'trigger' signal that BXD mentions. Is that the signal the causes the TV to AV switch? Is it a necessity?

    With regards to getting the required cables made up, are Keene Electronics or Lektropacks any good?

    Thanks again

    Mr Jubbly :rolleyes:
     
  9. MarkB

    MarkB
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    What's needed is the ability of the TV to force RGB input though a certain SCART socket
    configured through the TV's menu and without the switching signal…
    - OR -
    …instead of 3 phonos for component on the A/V amp, make 5 phonos for component/RGB.


    TV manufacturers take note.
    A/V amplifier manufacturers take note also.
     
  10. GarethRamsay

    GarethRamsay
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    Jubbly,

    You've got it right. This is how I have my setup running at the moment and the picture is very good. As mentioned before, though, you need to have a 'trigger' wire which tells the TV to switch in to RGB mode. As there is no way (at least that I know of) of passing this through the amp as well and keeping the Svideo free, you have to run another wire alongside which bypasses the amp and goes directly to your Scart into the TV.

    There is a downside, though, and that is that your SCART socket will always be in RGB mode whenever your DVD/Skybox/whatever is switched on. If you use any composite inputs to pass through your amp you will get nothing but a black picture unless you switch the RGB device off. Not a big problem, though.

    My TV also has two RGB Scarts (and one composite), however only one supports RGsB (where the Sync is on the green), both support RGBS. Also, only one of them supports S-video.

    Gareth
     
  11. MrJubbly

    MrJubbly
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    Gareth,

    Sounds like you have hands on experience of this, so I have a some questions for you:

    1) I now understand the ncessity of the 'trigger' wire, but you must end up with a pretty complicated cable arrangement. Would I be right is saying that the 'trigger' wire comes out ot the RGB Scart lead from the source and is connected to the RGB Scart that connects the TV to the Amp?

    2) What Pin on the Scart does the 'trigger' wire connect.

    3) Where did you get your cables from?

    4) Is the connectivity we're talking here known as RGBS?

    5) How can you tell what kind of RGB your TV supports? Can you tell from the pin-out diagrams? If so what should I look for? ( BTW my TV is the Panny 36PL30).

    Sorry for the braindump. Its just that fo every response I get there seem to be more questions buzzing around in my head.

    On a general note. I might be missing the point in all this, but I have to ask what is the point of supplying composite In/Outs on an Amp if you have to go to so much trouble to get things working. Is it because this sort of connectivity is designed more for projectors maybe? Very curious.

    Cheers

    Mr Jubbly
     
  12. MrJubbly

    MrJubbly
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    Can anyone answer my last post of questions?

    Thanks

    MrJubbly
     
  13. GarethRamsay

    GarethRamsay
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    No problem.

    1 - That's exactly it. Not a very elegant way of doing it, but it does suffice.

    2 - Pin 16

    3 - I bought a cheap £10 fully wired scart cable, cut it in half and then used a VU meter to check which wires were for which pins. Also butchered some old phono leads by cutting them in half and joining them up. Pretty bodged job, but I'm going to get some professionally made.

    4 - Yes. RGBs - Red Green Blue and Sync. RGsB is the other type where the sync is included with the Green.

    5 - Phone Panasonic as it's unlikely you'll find this in any of your documentation. Philips technical line was very helpful with me for my TV and their website actually had some reference material which I later found contained the data.

    Gareth
     
  14. Beamer

    Beamer
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    Be careful with pin 16! I just modified my Grundig TV this weekend to make one of the three SCARTS operate permanently in RGB mode. Before I looked at the circuit I was expecting pin 16 to take either an 8 volt or 12 volt switching signal. Turns out that pin 16 is a signal input with an impedance of 75 ohms and seems to be intended for a dynamic switching signal rather than a simple static line voltage. If your set is the same as mine you will draw 160milliamps and probably toast the 75 ohm terminating resistor by applying 12 volts!

    You can make a simple test by supplying 2 volts to the pin, if it switches to RGB then it's probably the same dynamic switching circuit as mine, you could also measure the resistance of the input pin to ground if you can borrow a meter from someone. I resolved the issue by removing the switching interface board and connecting the switching chip pin to an internal 2.5 volt source made up from a resistor divider and then to finish up I removed the 75 ohm termination resistor. Works a treat, BYE BYE S-VHS (at least for the digibox) :)
     

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