US SNES Multi AV to Japanese RGB-21 Cable

[teknix1]

Hi all,

I recently purchased a SNES Multi AV to US SCART cable in the hopes of modifying it to plug it into my XRGB-3. I had the hardest time figuring out what were the appropriate connection. I was hoping to find a schematic of the SHVC-010 cable (which is what I'm building here) online, but no luck. I couldn't find anything other than a few pictures of the insides of the cable, but not enough to make out the entire pinout. In the end I used GameSX's doc and managed to get it working but I still have two issues:

1. Fuzzyness/Bleeding in the image.
2. Audio noise that seems to be related to the video.

To make this cable, I used these links as reference:
SNES Multi-AV: http://pinouts.ru/Game/n64video_pinout.shtml
Japanese RGB-21: http://gamesx.com/wiki/doku.php?id=av:japanese_rgb-21

Before I go into more detail, here's my list of connections:

Multi-AV Pin # -> Japanese RGB-21 Pin #
1 (Red) -> 15 (With 220uF cap)
2 (Green) -> 19 (With 220uF cap)
3 (Composite Sync) -> NC
4 (Blue) -> 20 (With 220uF cap)
5 (GND) -> 21
6 (GND) -> 21
7 (S-Video Y) -> NC
8 (S-Video C) -> NC
9 (Composite Video) -> 9 (CVBS Input)
10 (+5V DC) -> 11
11 (Left Audio) -> 1
12 (Right Audio) -> 5
I also connected pin 16 (Ys input) and 11 (+5V DC) together on the Japanese RGB-21 end through a 3.3k Ohm resistor.

Back to the issues...

1. Fuzzyness/Bleeding in the image.
As you can see in this photo I took of Super Mario Kart, there is some bleeding next to the checkered pattern in the blue area. Also around the wheel of the kart. To me this is tolerable but I am just wondering if I could ground more pins on the cable or if there is any way to make it better. I also have to wonder if this isn't an issue with my LCD screen, but I don't have anything to compare it to.


2. Audio noise that seems to be related to the video.
Because I don't have my full setup yet, I am using my XRGB-3 on an LCD screen and don't have anywhere to plug in the audio. So I am using headphones plugged in directly into the XRGB-3. Doing so, there's a significant amount of audio noise when the game displays a bright image. It also goes away when a dark one is displayed. I had noticed this on a crappy old TV set that I own and didn't make much of it thinking it was a problem with the TV and not my system. I don't think there's much I can do since it's not related to this new cable I'm building, but I'm curious about the audio shield pins I did not connect on the Japanese RGB-21 side of the cable (See the links above). I'm also thinking perhaps this is a just how the SNES is...

If you look at my connections, you will notice there is an awful lot that is not connected on the Japanese RGB-21 end. Is this a problem, should I expect that most of the pins would be unconnected? If no one has a link to the real connection list for this cable, it would be awesome if we could document it here so that's it's easy to reproduce. At this point I'm either looking for solutions to my above problems or an official connection list for this cable.

Thanks in advance!
Nic

[RGB32E]

Use Micomsoft's pinout for the XRGB-3:

http://micomsoft.co.jp/xrgb-3_spec.htm

Pin 16 on the XRGB-3 isn't connected to anything and the XRGB does not use SCART switching, so you don't even need (shouldn't use) a +5VDC connection.

The audio line out should be clean, but I can't say the same for the headphone output... The XRGB line have been known to have noisy headphone amps.

[teknix1]

This is great information, thank you. I will be rewiring my cable tonight. I'll try to hit all the grounds pins too.

And for the audio, I'll probably eventually use a separate cable to go directly to my sound system.

Thanks
Nic

[teknix1]

So I've rewired everything based on the pinout of the XRGB-3, no change on the output quality or sound issue. Here's the new connections I've used:

1 (Red) -> 15 (With 220uF cap)
2 (Green) -> 19 (With 220uF cap)
3 (Composite Sync) -> NC
4 (Blue) -> 20 (With 220uF cap)
5 (GND) -> 3,4,7,8,13,14,17,18,21
6 (GND) -> 3,4,7,8,13,14,17,18,21
7 (S-Video Y) -> NC
8 (S-Video C) -> NC
9 (Composite Video) -> 9 (CVBS Input)
10 (+5V DC) -> NC
11 (Left Audio) -> 1
12 (Right Audio) -> 5

I did not use the 3.3K Ohm resistor this time.

Anybody has any information on the two ground pins on the Multi-AV connector? Could one be the video ground and the audio ground? That might explain why I get audio noise that seems related to the video displayed.

[BuckoA51]

XRGB3 loves composite sync rather than composite video for sync, where both are easily available you should always use the pure sync rather than the composite video.

[teknix1]

Awesome, I'll try making that change tonight.

Thanks
Nic

[teknix1]

Well I couldn't resist, I went ahead and made the change right away. I get the same result. I'll keep it this way though.

[bryan_c]

XRGB3 loves composite sync rather than composite video for sync, where both are easily available you should always use the pure sync rather than the composite video.

That seems to be system dependent; I'm not sure it's true for the SNES. Or at the very least, whether composite/pure sync would give a noticeable benefit seems to differ from system to system... maybe it's safe to assume using composite sync would never be worse, and would often be better.

I use an official SHVC-010 to connect my US SNES to my XRGB-3. It definitely uses composite video for sync (the pin for composite sync is missing from the cable) and let me assure you it looks great. I fired up Super Mario Kart and on the results screen I saw no blur from the checkerboard, and no colour bleeding that I could notice. Maybe a tiny bit of blur on the wheels, though not nearly as much as the provided screenshot... I'm assuming in my case it's because they're moving and my LCD isn't the greatest regarding motion blur.

Both ground pins are present on the cable; I'm not sure if one is for audio or if they are both connected to all grounds.

[teknix1]

Composite sync or composite video, I didn't notice a difference. For some reason I feel it may be because the RGBS lines aren't shielded. I will be buying a new SCART cable in the future and rewire the entire thing with better quality cable, including shielding.

Thanks Bryan for the info. I had given up on this but now I know for sure there's room for improvement.

Nic

[CkRtech]

Have any of you guys that are currently hitting the hardware forum worked much with RGB cables for the NTSC SNES? And by "worked" I mean dissected or built your own?

I was hoping to get some results from teknix1 if he elected to replace his cable with a higher quality cable.

I am currently working with a couple of cables wired for NTSC -> JP21 (I had to rewrite them both from SCART to JP21) and plugged into the XRGB Mini. I do have a bit of interference in the picture. It isn't too detectable, but it is there - maybe 4 broken horizontal lines of noise specks spaced across the screen vertically. I am pretty darn sure this is a shielding issue. If not, then it is a power supply issue.

Second issue is that the picture *seems* like it is overdriven. I know the gamesx circuit for the NTSC output calls for 220uf caps for the RGB lines without additional resistors. Have you guys stuck to this, or have you added resistors to the RGB output or elsewhere in the line? The signal seems quite strong. I am considering 75 ohm resistors on the lines along with the 220uf caps (very typical of output), but hoped to get some feedback from you guys if you would like to share.

[teknix1]

Hi CkRtech,

Funny that your posting this now, I actually had moved on to other projects for a number of months and didn't have much time to put into this until recently. I did purchase what I think is a better cable, not sure if it really is, but at least this one is shielded. Unfortunately it didn't yield any better results. Actually, plugging my previous "version" of the cable into my XRGB3 gave me some weird artifacts sort of like the jailbars that can be seen on modded NES for RGB. I had never noticed those before and I doubt they were there a few months ago. They're pretty obvious. I wonder if it could be a bad setting on my XRGB3. I can't really explain it. I tried with a second SNES and got similar but different results. I tried replacing the caps with different quality ones, I bought what is considered to be the best caps brand from digikey but it didn't change a thing. There is a schematic for the video output of the SNES. I'm hoping we could get to understand the circuit better and come up with a better filtration of the signal than simply putting a 220uF cap in series. See here: http://members.optusnet.com.au/eviltim/ ... _snesn.png So for now I'm kind of lost because I do not have the expertise to understand the video output. I do have a friend with some of the know how, but I need to find time to get him to look at this...

Nic

[CkRtech]

It is tough to hear that you didn't have success with your changes. Obviously there are other possible issues such as interference earlier in the circuit (inside the SNES), a low quality power supply, bad...voltage regular - who knows?

The best thing I have read so far has been from Link83, viletim, and our own RGB32E on nfggames.com I believe it was.

I am certainly willing to try things out, but I really only know enough to be dangerous. It would be fun to stir up interest from those that are and try some experiments.

[teknix1]

I finally had some time to dedicate to this cable once again. I decided to start with getting rid of those strange jail bars, so I went in my gefen scaler, tried every option, then did the same with my XRGB-3. I got lucky with one of the last options, Low Pass filter, you definitely need that enabled. Everything became beautiful again (well I'm still having some bleeding like before, but it's more than acceptable).

Then on to the cable, I thought it was time I had a finished cable, after all I do need to play some SNES and N64. One thing I wanted to do is build one with RCA outputs for audio. The XRGB-3 isn't especially good at audio so I wanted to go straight to my receiver instead. My SNES has S/PDIF output already (this is so great, I wish the same could be done to the N64, oh well...), so no need for those RCA outputs here, but since I'm using the same cable for the N64 too then I need an alternative.

Here's what the cable looks like now.

For the audio, I simply drilled holes on the side of the SCART connector and connected the audio through there.

Here's a couple of specs about this cable:
The cable is shorter than the regular cable, about 3 feet long.
The cable used is 24 gauge, 8 conductor, shielded (one big shield around all the conductors, couldn't find one which individual conductor shield)
The shield is connected to the ground pins on both sides.
I used Panasonic caps, I made sure to use 10V caps as it's pretty crowded inside the SCART connector. You might be able to get away with 16V caps.

The connections used are as follows:
Multi-AV Pin # -> Japanese RGB-21 Pin #
1 (Red) -> 15 (With 220uF/10V cap, ne)
2 (Green) -> 19 (With 220uF/10V cap)
3 (Composite Sync) -> 9 (CVBS Input)
4 (Blue) -> 20 (With 220uF/10V cap)
5 (GND) -> 7, 13, 17, 18 (And ground on the RCA connectors)
6 (GND) -> 7, 13, 17, 18 (And ground on the RCA connectors)
7 (S-Video Y) -> NC
8 (S-Video C) -> NC
9 (Composite Video) -> NC
10 (+5V DC) -> NC
11 (Left Audio) -> White audio RCA connector
12 (Right Audio) -> Red audio RCA connector

At this point I am very certain that any artifacts/blurring that I get aren't coming from the cable. Shortening the cable or changing components, from the crappy caps that came with the decade old cable to the supposedly best ones, made no difference whatsoever. As I'm pretty happy with what I've got now, I probably won't spend more time on this problem, except maybe playing around with the XRGB-3 settings. ...or unless somebody posts a good solution online.

Hope this helps!
Nic

[RGB32E]

The best solution is to get the right SNES revision! What is the serial number of the console you're using? The best RGB is available on the one chip revisions and modded minis. I had thought at one time that taking RGBS directly from PPU2 and buffering with a THS7374 would make any SNES look great. However, after hearing about someone trying something similar with a Sony CXA1645 and not getting better PQ, I decided not to bother... The idea being that regardless of the buffering circuits and encoders used in a particular SNES revision that the PPU outputs fuzzy signals. However, using a THS and bypassing all of the circuitry could give better results!

[teknix1]

That's interesting. I have two SNES:
UN278934465
UN14831830

I swapped parts between the two systems years ago to produce a better looking SNES, one had the top yellowed but not the other one, etc... So I don't know which SN# goes with which main board anymore. Anyways, the better of my two system has some minor bleeding like I pictured earlier in this thread, the other one is just completely awful, there's this checkered pattern and the bleeding is very excessive all the time. What do these serial numbers tell you? What is a good serial number?

It's been a while since I opened my snes but if I remember correctly, the S/PDIF mod requires to have the multi chip SNES, I would think that's the model that I have.

[Ed Oscuro]

There is some way using some commercial software to get a display of the SNES system's version. Looking for more information since I forget the details. No promise that'll be helpful, unfortunately.

[CkRtech]

Although several lists of SNES serial numbers exist, I used this one by DarthCloud of assemblergames.com: https://docs.google.com/spreadsheet/pub ... utput=html