Yeah, you're right, grahf... Bad idea. I asked him about it to be sure:
I have sold at least one in the past for use with the TurboDuo, but they also used one of the sync-cleaner boards, I don't know if it's required to be honest as I've never tested it myself.
From a quick read about the if the sync is very low level, then the encoder may not be able to detect it at all. Also the issue of low RGB levels output from the Turboduo sounds like it would almost certainly need an additional video amp, which the board does not include.
He wanted $50 bucks for the RGB-to-Component-only version BTW, but if you have to play around with an Amp and need this "sync-cleaner", with that level of uncertainty, it's not worth it... I'm the last person that would be able to figure it out. I guess you gotta go with those external devices you see floating around eBay.
@Keith: Yeah, the ones that I was looking at had regular Composite RCA jacks, they didn't have S-Video, though. They're not bothering with S-Video is what I was pointing out - it seems that connection standard might be on the way out with newer TVs.
Anyway, I'll just do the S-Video mod for now. Spent about $5 bucks so far, minus a female S-Video mount which I still need to find.