Otdfbt

I was exploring different options of connecting both my Atari ST and C64 to a modern TV.

I opted for a composite signal passed through a cheap AV to VGA converter, and although the display works, there is this crawling dot problem, which as I understand is specific to the composite signal output itself.

Atari 1040ST AV video output - blurred and jagged vertical edges

Since then I spoke with few people who recommended getting RGB SCART cable with a SCART to HDMI converter, however on of the reputable sellers on ebay advised it will not work:

This youtuber compared few options and concluded the best output will be passed using ST to vga, then vga to hdmi using simple direct cable mod.

https://youtu.be/c25dlHFW584

I'm looking for a best solution that will not ruin my pocket (going over £60) but will give a clear, sharp image on a modern display.

Can you suggest some parts, please? If I understand correctly not all converters are the same, there are also scallers? Are there any particular characteristics of a component to look for?

My monitors and TVs can accept VGA, DVI and HDMI only.

For the ST, the best option I’m aware of is to use the Atari-provided SCART cable and the OSSC; the latter will double lines etc. to produce a picture which any modern HDMI screen should be able to display.

Depending on the outputs from your C64 (which may need to be modded anyway), the OSSC might not be appropriate; the RetroTINK 2X supports S-Video, composite, etc., but there are issues with the current firmware and C64s. I’d suggest waiting for VGP’s forthcoming Koryuu.

None of these fit within your budget...

If you're willing to modify the C64, there is a fairly recent mod that replaces the C64 modulator circuit with an FPGA board that generates an additional YPbPr signal by snooping the VIC-II chip signals.

You don't mention what inputs your "modern TV" has, but component/YPbPr is more likely to still be supported rather than S-Video which is your other option for a better quality picture on a C64 over the composite signal. If you need HDMI then the well-regarded OSSC can at least use YPbPr whereas it doesn't support composite or S-Video.

Sony DSC-1024 works great with both ST and C64 (or any other retro analog video). Outputs to VGA CRT, LCD, etc. Can often be found used for <60 GBP. You'll need the right cables for the computers.

This is professional gear that used to be popular with broadcast studios. That's why the analog (VGA) video that it outputs is relatively "pristine", even when upscaled to 1280x1024 resolution. It even reproduces composite color artifacts. Naturally, any interference in the input signal is also visible at the output. That's why you should obtain the right cable for your computer, such as RGB for the ST and S-video for the C64.