I haven't tried, but I think this supposed "ground loop" is on the Super NES board(what exactly is a ground loop and how do you eliminate it?). I once tried to hook up the Super NES Composite and S-Video straight into the RetroDuo's Composite and S-Video jacks, but it did absolutely nothing to eliminate the static. But from what I heard, not all RetroDuos are made equally, and the hardware varies between paint jobs. Some RetroDuos supposedly have no such issue with static on the Super NES side's video output, and I remember one of the older RetroDuos(those that come in this box: http://www.itechnews.net/wp-content/upl ... ulator.jpg
) having no such problem with static on the Super NES side's Composite video. The new ones(with this boxart, which is the RetroDuo I have: http://imgs.inkfrog.com/pix/gamedepot/r ... hite_2.jpg
) also have bad video off the NES side unless you add the resistor and capacitor to the NES side's audio circuitry. The video itself is sharp(although a little washed out), but without those parts, you will get diagonal strips on the screen that scroll from left to right on top of waves that are in sync with whatever sound is being output from the system.
A word of note(and probably unrelated): I don't plan to make a portable out of my RetroDuo. If anything, I'd use my FC Twin because I can't fix that damn thing's NES sound circuit(every time I do, it works for about 2 minutes before the sound wants to cut out completely; I get nasty popping noises and A LOT of hissing), but the Super NES board still works perfectly.
I'm just curious: has anyone replaced the KA2198BD in their RetroDuo by the Sony CXA1645(they should be pin-for-pin compatible)? If so, was there any improvement in the video quality?
I have a spare PSX model 5501 that has the Sony CXA1645M in it and a Retro Duo I don't mind experimenting with. Do you have any tips on desoldering the chip from the PSX board?http://i55.photobucket.com/albums/g157/ ... 1e5e60.jpg
Desoldering surface-mounted components is one thing I absolutely HATE to do. Every time I use my soldering iron to desolder a surface-mounted chip, not only does the chip come off the board, but so do the traces that the chip was on. Instead, I just stick an X-acto knife behind the pins on said chip and push outwards. The pins will break off the solder without breaking the traces. Just don't apply too much pressure because then, you might be able to break the traces too.
Report back when you're done about whether the static is eliminated or not. I know Samsung made some really nasty encoders(the KA2195D comes to mind; was used in the Genesis Model 2 and resulted in the worst Composite video I have ever seen. THE ENCODER DOESN'T EVEN OUTPUT S-VIDEO!), so I'm wondering if the static is actually caused by the encoder and not the circuitry around it(I know the CXA1645(used in the Yobo-branded FC Twins, late Genesis Model 2s and the Genesis Model 3) outputs VERY SHARP Composite and S-Video, so if there's still static in the video, we can confirm that the circuitry on the RetroDuo is causing some sort of interference).