You always have some sort of lag with any kind of electronics.

But since it's analogue to analogue there should hardly be any.

So you're using the video in and outputting it onto VGA? Yes, there will definitely be a delay.

There will always be lag on paper.
That being said, with a crt I'd be more worried about image ghosting.

Depending of the output resolution, there be more/less input lag.

low resolutions (640x480) are equally similar to TV "resolution", there is the minimal input lag you can achieve.
try to pass-thru the signal, don't apply filters, post process, color correction, deflicker, nothing.

I don't now if you can put a old console like nes, with 240p output image, probably the card don't handle this.
if was, the card will try to deinterlace to 480i, then use the frame buffer to make 480p...lag everywhere 😵

if you use a console like a ps2,wii with 480i output, the card will try to make it 480p, less lag
if you use a ps2, wii with progressive output (480p), the card (if can handle) theorically don't make anything and probably your are lag quasi-free signal.

Try by yourself.

Regards!

This is a very interesting idea. I use a CRT monitor for lots of things still. I also have an NES and a Genesis and I'd love it if they looked better without having to find space for an old TV. Old consoles look horrible on my LED TV.

I have a 3500 with the breakout cable. I'll give this a try some time but I have no experience with video in\out on things like this.

I found a review of the 3500 and it sounds like the input quality may not be that good. Probably still worth trying though.

http://www.anandtech.com/show/351/15