Re: Build your own Amiga-VGA adapter?
What would be even better, but probably quite expensive, would be to work out how to convert the Amiga RGB output into component. That would give the best results on larger screens, because even using S-Video you are degrading the image slightly.
Component works by sending the video data though 3 cables. These are not RGB signals as some think because of the wiring colours, but instead are YUV. This works by sending the Master Y (black/white) Luminance signal down one wire, normally Yellow or Green, and the U (R-Y) and V (B-Y) signals (the colour difference signals) down the Red and Blue cables.
S-Video in contrast only sends the signal through 2 wires. One carrying the Y Luminance signal and the other carries a multiplexed version of the two colour-different signals. Therefore there is more chance of interference and signal mix up with the signals being combined down a single wire for the colour difference.
Taking video output in general, the SD PAL resolution is 720x576 (and NTSC 720x480). Firstly with composite you are lucky to clear 250 lines, ending up with about 240x576, which explains the bad blurring and degradation of colour on composite connections, and is about par with standard VHS recordings. Next S-Video is a much cleaner signal, but even this will only give you about 480x576 at the most from a good quality source, so you are still losing some resolution and degrading the image. Component and RGB SCART are the best output sources as both methods separate the RGB values and carries them between the source and destination along separate wires to remove nearly all degradation caused by noise and multiplexing. In addition the luminance and colour difference signals are also carried separately, so you get the cleanest signal at the other end.
Component and RGB Scart are pretty much identical in quality and output resolution. Therefore if you only want to output standard definition signals from an Amiga to a TV then an Amiga to RGB Scart cable will give the best results and is the cheapest option. No addition conversion needed. Converting to S-Video with one conversion box, and then upscaling the resulting image to VGA will in fact give you a worse picture than just connecting the Amiga directly via an RGB scart cable directly to the TV and letting the TV upscale the image to its panel resolution itself.
Obviously, if you need to output the Amiga signal to a VGA monitor, or wish to access the higher resolution modes without flicker, then you do still need a conversion and upscaling box of some sort. But the conversion to S-Video and then to VGA is not the ideal solution as you are converting the signal twice, and therefore degrading the signal each time, reducing colour accuracy and overall line resolution. But if only being used for Amiga games an RGB scart cable is in my view a good cheaper solution.