I got the
RGBHV/RGBS to Composite/S-Video converter and it works really well. I was expecting a shoddy POS but it works exactly like it should. I tested it last night with my AV Famicom, SNES and Genesis.
I have the converter connected to the fourth output of my switch. The converter itself has two separate outputs: Composite and S-Video. I first connected the Composite and S-Video to a single monitor and tested switching signals back and forth without any problem. Then I connected the Composite to another monitor to see if it could display its two signals simultaneously on two different displays, and that also worked fine. It was really neat seeing Composite, S-Video and RGB all at once from one console.
The Composite signal itself is as clean as I have ever seen it. It looks quite good on both NES and SNES, pretty close to S-Video quality except for some dot crawl and extra degradation. Genesis is more of a mixed bag. It's better than what I remember of the native Composite but I'll need to get fish out my Gen Composite cable and really compare. There's pretty severe rainbow banding on the waterfall in Sonic and the "shadows" in Comix Zone, but I believe this is a problem inherent with the source itself and not the converter. Some quick research indicates it's either aging caps in the console, RGB cable interference, or possibly the Composite encoder chip in the Genesis interfering with the RGB signal.
"Sadly" the signal is clear enough, or my monitors clean up the Composite signal so well, that some of the assets don't fully blend to make the intended transparency effects... Sonic's shield, bushes, Sonic 2 palm trees. Although I just remembered my BVM has Composite inputs on one of the video cards with full control to turn off comb filters and manipulate the Composite signal. I'm not sure if this would make any difference but it's worth a try.
I was briefly getting a very wavy picture with bad color bleed, but after moving it around to checking all the connections it went away. I'm attributing that to interference from all the other equipment and cables nearby.