http://www.datavideo.us/products/tbc_3000_main_page.htm
i got one of those. adding to the full frame TBC, it has contrast & colour gain.
HOWEVER, there was still 1 old commercial vhs that it only partially helped. for this particular tape, due to heavy macrovision, the TBC could only manage blacked out top half, meaning the image starts halfway down the screen, and also not that stable!
if i get a chance, i'll post an image.
so be warned that if you go down the TBC route, there is NO GUARANTEE that it will defeat the macrovision and give you rock solid images/feeds.
but i suppose for $20, you simply can't go wrong?....