PAL SNES Cable thoughts

Started by Cloaked Alien, September 28, 2009, 12:27:58 AM

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Cloaked Alien

I was recently informed that the PAL SNES supported RGB output. And me having a 46" Samsung LCD naturally wanted the best picture quality possible out of my console =)

I've been reading up and I know all about the diagrams and the "official" RGB cable configuration, modding gamecube cables, etc. But when when I got down to business it wasn't quite as clear.

I myself bought a couple of pre-modded cables

One didn't work properly (the bugger forgot to desolder the composite capacitor) and the other worked pretty much as well as the first one after I fixed it.

However, there was one clear issue. The picture looked.. "pixelated".. "dithered" or what not.

Then I got a hold of an unmodded 3rd party Gamecube cable to test for myself

And all I did was to desolder the capacitors and it worked (in my opinion) a lot better!

Now I remember reading on these forums (or some other) that some leads have built in resistors between composite and ground, which these good cables actually have (I verified with a multimeter) so that's really the only difference between the two cables.

I also noticed that the two "bad" cables doesn't even have a pin for ground in the snes connector so they can't be modded to work in the same way! Bastards...
Edit: I just noticed that only one of the cables where missing pins, the other one has a full set. Pretty weird though.

Anywho, when I started to ground R, G and B the picture on the good cable started to look like in the first pic again.

My personal preference is obviously with picture nr 2, but I'm hoping someone could shed some light on the technical details behind this. How is it supposed to look? Maybe my Samsung LE46A656 has a daft scaler? (and the other 50" brand TV at work I tried with, which is not very likely).

Any information would be greatly appreciated!


Cloaked Alien

Quote from: viletim on September 28, 2009, 03:48:32 PM
Super Nintendo PAL and NTSC RGB cables are different. See:

Thanks viletim, but I know, that's why I desoldered the capacitors, otherwise the cable wouldn't have worked at all =)

Question was rather centered about the difference in quality between my two screenshots.


I'm having a hard time following your post. It's not clear what you're talking about when you mention "good" and "bad" cables.

Cloaked Alien

Fair enough. Here's the simplified summary =D

I hope you can see the pictures in my first post, as those are crucial.

"Bad": First picture. Cables without resistance between composite and ground

"Good": Second picture. Cable with 75 ohm between composite and ground

Question: Why is this happening, can I improve on it? Obviously most people seem to be satisfied with the results I have in the first picture, that's how most of the pre-modded cables you buy seem to work.

Oh, and if I'm not mistaken you're the one maintaining the Game Console Scart page? I've been looking at that all along and actually did try to construct a 100% diagram replica, but the picture quality went from "good" to "bad" again. So I'm not really sure what to expect, maybe I just messed it up.

Mind you, I didn't use 75 ohm resistors (These are hard to find for some reason), but I was close to it (60-something)


Yeah, I maintain that page.

When using composite by itself on a PAL console without the resistor in place the picture usually looks washed out or lacking in colour. RGB without the resistors just gives you too much contrast, sometimes with other artefacts which occur when overdriving a picture tube.

When the video is being digitised things become unpredictable. The noise on the signal without the resistor on the composite line could be the DSP going funny with a bit of an overload... I can't explain why it looks bad when you try to replicate the cable from my diagram. I don't have any SNES hardware with me at the moment so I can't tell you which more accurate. I'd suggest using composite video (with an official cable if possible) as a guide.

A 68 ohm resistor substitution won't make any significant difference.


Hey.  I know it's considered bad ettiquette to bump a 3 year old post, but seeing as I would be referencing a lot of this information anyway, it makes sense to do so in the same thread.

I'm having the same issue, and I'd like some clarification.  I'm using what appears to be exactly the same model as OPs "good" cable, but I'm getting the same pixelation effect as the "bad" cable.

I  modified the Gamecube cable by removing the capacitors, and I get the pixelation straight away.  Then, seeing Viletim's pinout diagrams, I added 4 75 ohm resistors to the R, G, B and Composite pins as in the diagram, but it made no difference.

I also get a loud buzz when the screen is displaying colour, which disappears when the screen displays black.

Here's a picture:



Am I to understand that this should be overcome by the 75 ohm resistor to ground on the composite pin?  Should I try a higher resistance?

Oh, and it's worth pointing out that there is one main difference between my cable and the diagram - I don't have a 5v wire.  That pin is wired to the 12v via a resistor with a heatshrink tube over it, so I don't know the value.

Cloaked Alien

I'll probably get hanged for bumping this myself, but I actually revisited this recently when constructing a new RGB cable for a friend.

From my experience the "good" version looks "bad" on my more recent Samsung TV.

I think I emailed back and forth with Viletim back in the days, but I'm to daft to understand the gist of it. I think the SNES uses composite signal for sync with RGB and that somehow interferes?

Still, the graphics looks dithered and I've been thinking if it's supposed to, relying on CRTs mixing the colors and if emulators even emulate this to avoid the dithering?

Anywho, it would actually be interesting to hear someone take an ELI5 (Explain Like I'm 5) approach to this.

Cloaked Alien

Sorry to bump this really old thread, but I feel this is relevant in case anyone comes across this thread.

TL;DR; Issue is caused by "Sync on composite" and can be easily fixed. Laziest way is to just buy a cable that uses CSYNC (Composite Sync) instead.

"Demystifying RGB & Sync - MY LIFE IN GAMING"