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Thread: RGB > CVideo,S-Video and VGA, self made!

  1. #11
    Amibayer! Bryce's Avatar
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    I think what AmmoJammo is trying to say, is that the A600 and A1200 contain a CXA1145 which can also give a very sharp S-Video signal, you just need to add the S-Video socket and make three connections. This is how I connect my machines too.
    I would also be interested in learning more details about your PCB and what ICs you've used. I think your card is more interesting for A500 users, that really don't have any decent outputs other than the standard composite and RGB.
    I also produce a very similar PCB with just S-Video output, but it is based on the AD724, which you obviously aren't using (it's only available as SMD).

    Bryce.

  2. #12
    Amibayer! Bryce's Avatar
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    Sorry for the double post, but I was looking at your PCB pictures again and I can't see any line impedance resistors on the circuit board?? How are you achieving the 75Ohms without these?

    Bryce.

  3. #13
    Halo: ODST Inactive Member
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    Hello, nice skills mate, are you planning on getting it commercial or open hardware?

    If the later, can we have, please, the schematics ? xD
    Money surely dont bring happiness, but if you have money you can buy any kind of mizery you like!

    Join us on IRC @ irc.ecs.soton.ac.uk #Amiga

  4. #14
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    Hello status,

    your question is right, but i am not a profi and this device is very simple: it is a little bit more then a Sony test board (the ic is a Sony CXA). I have put it on sale here

    http://www.amibay.com/showthread.php?t=49019

    why to made this device i have spent much time and a few money to purchase the components, that are new. That mean that the schematic of this device has not much value.

    Regards
    Stefano

    ---------- Post added at 15:09 ---------- Previous post was at 15:06 ----------

    Quote Originally Posted by Bryce View Post
    Sorry for the double post, but I was looking at your PCB pictures again and I can't see any line impedance resistors on the circuit board?? How are you achieving the 75Ohms without these?

    Bryce.
    Hello Bryce,

    what you search is on the bottom side of this device.

    Regards
    Stefano

  5. #15
    Amibayer! Bryce's Avatar
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    Ah, tricky. I didn't realise you'd put SMD components underneath. Nice solution.

    Bryce.

  6. #16
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    Hello,

    i have some unsolved questions about this device and a reply from experts is more then welcome.
    I have tested the SVideo output of this device on one of my television (a big Samsung LCD TV, of the year 2005/2006), with an SVideo2SCART adapter (that is very easy, without electronic devices inside). This TV has two SCART input and, on the first SCART connector, the SVideo output of my device is properly recognized: the picture is bright, colorful and sharp, without flaws of colors, very beautyful, like an SVideo source is.
    On the second SCART connector, the SVideo output of my device is not properly recognized: the picture is bright, but with flaws of colors and sometimes, there is a loss of colors (only the luminance signal is displayed).
    I think that on this second SCART connector, the video signal is interpreted to be a composite signal and showed with a loss of quality.

    I have read that this is normal with televisions with two SCART input.

    I have another LCD TV, cheaper, with only one SCART input connector. On this television, the SVideo output of my device (through a SVideo2SCART adapter) give the same picture of poor quality, like on the second SCART connector of the big Samsung TV.

    Someone has tested this device with a Benq projector, that come with a SVideo input connector, and then, compared the picture with the quality of a CD32 (that has SVideo output built in): the consolle of Commodore show a better picture, and my device is not properly recognized. It show a picture like a composite source.

    I think that this projector, through the SVideo input, manage the picture like a composite picture (add luminance to the chrominance like a CVideo input), then the result is a picture with less flaws of colors on CD32, but more blurried, like the CVideo output of this Amiga.
    This is my theory, and not confirmed. If someone of you know this matter, your reply is welcome.

    Regards
    Stefano

  7. #17
    Amibayer! Bryce's Avatar
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    Hi Vibros,
    can you possibly make a screenshot of the output signal on an oscilloscope, with some sort of voltage reference?
    Also can you tell me what IC you are using to convert the signal or even better, could you send me the schematic and I will check it against a reference design (I will not pass it on to others or whatever if you want it kept secret).

    Bryce.

  8. #18
    Inactive Member scap61's Avatar
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    i'm from Piacenza Italia and i'm interested about your device

  9. #19
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    Hello,

    a little update with review.

    The outputs are three, always active: is responsability of the user do not damage the video device.
    The output are CVideo, S-Video and VGA. This adapter is not a scandoubler, so the VGA output is active even if the signal is about 15 KHz on the horizontal sync.

    Now some pictures from a CRT monitor (with a SCART2CVideo/S-Video adapter):

    the CVideo on the Early Menu screen

    Click image for larger version. 

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    on a HiRes Workbench

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    on DPaint

    Click image for larger version. 

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    The image has flaws. There is a regulator on this adapter, to gain the best quality on CVideo. VGA output is not affected and it has ever the best quality.
    Anyway, as already wrote, CVideo image is sharpe and clear, much better then the original CVideo output from an A600/A1200. To paint with a paint program is very easy and funny: you have just an easy cable with an RCA connector. The quality is ok!
    On a Workbench screen, the characters of a text, where contiguous pixels alternate dark and white colors, give more flaws, and the quality of the image is less clear.

    The S-Video on the same CRT monitor with the same adapter from a SCART connector: the monitor do not understand the S-Video input, just the luminance, and the picture is gray!

    Click image for larger version. 

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    Now CVideo on a LCD monitor (on this monitor a resolution of 640x512 is very stable,without flicker)

    Click image for larger version. 

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    and S-Video, more clear and sharp, very good indeed!

    Click image for larger version. 

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    As said, VGA output is the best, with no reduction of quality. Refer to the pictures on the previous posts!

    Thanks for watching!

  10. #20
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    Do You still have it?
    I am interested in. Where is photo of device?

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