cvgl wrote on 2020-04-17, 18:59:
What converter could I buy that would correctly convert a VGA image from DOS games in 640x480x60, 640x350x70, 720x400x70 resolution? Ultimately, I want to connect it to the AverMedia card.
I have been on the lookout for a similar converter and tried several of these cheap solutions (The dime-a-dozen black/white box type you can find everywhere on ebay/ali/amazon etc) None of those seem to support 720x400 70hz textmode until I came across this one at a local electronics store;
It is made by Sanwa Supply (not to be confused with Sanwa Denshi of the arcade switches/buttons) and while it looks identical to the aforementioned dime-a-dozen bunch, this one actually says on the box that it supports 720x400 x 70hz and to my surprise was one of the only manufacturers who openly state all their supported modes on their packaging. The model number is VGA-CVHD2 and is reasonably priced at around 4000 yen or around 35 eur. They can be found on Amazon.co.jp.
Mine should arrive tomorrow and I will update after I've given it a shot 😀
I've tried the Sanwa Supply converter and this too wouldn't display anything before the OS (i.e. BIOS/POST/DOS etc..) Despite all the claims of the resolutions supported on the box.
However, another box that I had ordered along with it did turn out to work and it was the cheapest of the bunch! Lucky!
The monitor I'm using recognized the BIOS / POST resolution as 640x416 x 70hz rather than 720x400x70 which sounds hella weird but hey, that's what the monitor said, and it actually displayed, unlike all the other boxes.
The box that worked looks like this and cost me 999 yen or like 8-9 eur.
Though even the one in the picture has a green audio jack on the side whereas mine is just a normal metal looking one.
I believe many of these are just reproductions from a lot of different manufacturers based on similar designs using a variety of components and materials...
My advice however is buy a bunch and try them, since they aren't always true to their claims on the packaging / product information.
Ideally from a store where you can get a refund for the ones that didn't work.
I'd really like to see a teardown on a bunch of these to identify what signal processor the good ones use, so people interested in getting them can know what to look out for.