DaytimeDreamer
Southern Pounce.,
- Joined
- Jul 22, 2005
- Posts
- 747
Awesome stuff! Many thanks for this.
BTW I spoke at length about my 3-3 bypass mod with an experienced EE on the subject. He gave my mod a thumbs up as being definitely viable because I made sure to attenuate the brightness. He says the only thing is it won't be entirely 'perfect' on very technical and minor details, but that this is far outweighed by the improved visual clarity over the CXA's jail bars. The only thing he suggested adding is some 220uf caps purely for protection against idiocy, but that technically it doesn't need them otherwise. Here are some snippets of his comments:
Driving straight off the DAC should also be within spec, as long as your attenuation is correct.
The Neo Geo DAC output is a bunch of LS gates connected to each other so they are already sourcing/sinking into themselves. So using or not using a series cap would be negligible to performance. It's safer to use a cap, so I would still leave it in. 120uF minimum, but I would use 220uF. Can use 470uF if you want to go crazy. Can also leave out the capacitors like you have it now. They are not necessary. It's just for added protection in case some dum-dum heads hook things up wrong on the other end.
The trade off for simplicity in driving the video line directly off the DAC gates is huge. You still have impedance mismatches and non-linearity, but it's still better overall than the junk noise you get stock.
And with that, I'm betting the 3-5 bypass mod is subject to the same issues about impedance and non-linearity. However, the resulting picture looks so much better than stock encoder that as I said, the benefits far outweigh the negatives.
So here's more eye candy from my bypass mod optimally timed by the OSSC:
Thanks so much for all this info FBX I have an AES 3-4 board that is stock and I am thinking of doing both the audio and RGB mod. One question I have is it seems that you are using an OSSC for testing the RGB result. Have you also tried it out on a PVM? Just curious if the results are still good. My aes gives off a dim picture now in RGB. I was fixing a friends neo geo cd and that system with the same scart cable gave off a beautiful RGB picture.
What are your optimal OSSC timings for your Neo Geo 3-3 by the way?
Great, thanks for sharing those settings. Don't you like the scanline look? I'll experiment a bit with scanlines but first I must update my OSSC firmware. I'm still on 0.76
Thanks for the response FBX I am going to order the parts to do the mods. I am going to get a NEOSD soon so I wanted my aes to perform at it's best.
Have you also tried it out on a PVM? Just curious if the results are still good. My aes gives off a dim picture now in RGB.
Finally got around to hooking it up to my 20M2U and it looks frikken beautiful! Bright and vivid colors on default dial settings.
That said, remember again that the brightness attenuation is simply a matter of changing those resistor values. So if your 3-4 ends up looking too bright or too dark, you know what to do. :-)
I updated my web page article (hit refresh on the browser to make sure it's updated) to show my installation of 220uf caps in the SCART head of my RGB cable. This is to provide protection against voltage backflow from failing equipment, and does not change the picture quality or brightness at all:
Neo Geo AES3-3 RGB Bypass Mod