I use an Amiga 500 connecting to an LCD screen via the A520 modulator (I live in Canada no SCART).
Now these things are usually terrible when it comes to quality, and mine was too when I first started using it. But for some reason it has cleared up significantly after about 2 months of use. I mean I use it in High with Interlaced mode and its very good.
Now I recently received another A520 from my Amiga club and used it for comparison. The new one is terrible in quality, very blurry. So my question is do these things get better with use, or did I just get lucky with the one I have?
I don't know why one A520 would be better than another, but if I were you, I would look into buying yourself an IndivisionECS to use instead of that A520 display adapter. Jens of Individual Computer's has done some real magic with the IndivisionECS and it will give you some display choices with resolutions not available on any other ECS Amiga without an IndivisionECS.
Then keep your eyes focused on what the Apollo Team are doing with FPGA based accelerators for many different Amiga models and buy one that fits your A500 when they are finally finished and released for sale to the public.
