Sega Genesis Audio Quality - The Problem

[evildragon]

Originally Posted by Joe Redifer

Off topic - The SoR2 "bar lights" are not "smooth" via RF or composite unless it is on pause. If any character walks behind them or the screen scrolls, it looks super grainy and you can tell exactly what's going on.

That's because RF sends the picture on the audio subcarrier, just encoded differently.. sound is FM radio, picture is AM radio...

[evildragon]

I think I also know why the audio quality changed when they added the license screen..

Obviously, adding a ROM BIOS to the system required a redesign of the circutry.. Since they would be spending more money to add a ROM chip to the board, they decided to cheap out on some of the parts.. While the 2612 in it is the same, the crystal obviously was a little weaker.. Not only that, in this revision, they added a REAL moto 68k, where the original had a clone..

If anything, it may be possible the crystal was the SAME, but using a real Moto, which everyone knows that the 68k is a power sucker, it might have drawn WAY too much from the crystals clock, OR it's own power (which then leads to weak clock generation)..

That's my guess..

[TheGZeus]

Any chance of a 'how-to' tutorial? Or did I just miss it...

[Joe Redifer]

Originally Posted by evildragon

That's because RF sends the picture on the audio subcarrier, just encoded differently.. sound is FM radio, picture is AM radio...

Noooo... that's because the bar lights are dithered. RF can't hide that. Nor can composite or any other video format. Looks great on pause, but like I said earlier, when the screen scrolls or there is motion behind the lights, the dithered mess that it truly is comes into play. To be honest I'm not sure why they went the dithered route for those lights. They could have simply used the highlight feature for true "transparencies".

[evildragon]

Originally Posted by Joe Redifer

Noooo... that's because the bar lights are dithered. RF can't hide that. Nor can composite or any other video format. Looks great on pause, but like I said earlier, when the screen scrolls or there is motion behind the lights, the dithered mess that it truly is comes into play. To be honest I'm not sure why they went the dithered route for those lights. They could have simply used the highlight feature for true "transparencies".

wait, i thought you were talking about the audio sounds were messed up when the genesis was playing, but on pause the sounds were fine...

my bad, yea, i know it's because of the composite/RF issue.. i don't believe the highlight mode can add color, only just make something brighter, or darker, but not add yellow coloring (if I remember your screenshot)

[evildragon]

Originally Posted by TheGZeus

Any chance of a 'how-to' tutorial? Or did I just miss it...

im not good at tutorials.. i'll try though..

[TheGZeus]

Awesome.
Well, take pictures of the places that need modification, then under it, say what to do there.
A seperate list of the order they need to be done in and that would be suficcient.

that would give people that somehow enjoy making them what they need.

Also, I'm more interested in doing this to a Genesis 2, I'd like to keep my High Definition Graphics model stock.

[evildragon]

if you have the HD Graphics model, you don't really need to do this.. Unless yours sounds like the "Before", which it shouldn't.. The HD Graphics model are notorious for being, good..

This can't be done to a model 2, it has a cloned 2612, not even a YM model, and it's in the 315 chip..

[Joe Redifer]

Originally Posted by evildragon

i don't believe the highlight mode can add color, only just make something brighter, or darker, but not add yellow coloring

You are correct! It would have to be a white light instead of a yellow light. But would you rather have a white bar light with true transparencies using space-age technology from the future given to us by evolved aliens or yellow lights that look ugly as all hell no matter how you have your system hooked up?

[evildragon]

well, was this game from an arcade game? if so, they probably didn't want to go in and bother recoding a light...

[Joe Redifer]

Nope. Programmed from the ground for the Mega Drive up by Yuzo Koshiro's friends.

[TheGZeus]

Originally Posted by evildragon

if you have the HD Graphics model, you don't really need to do this.. Unless yours sounds like the "Before", which it shouldn't.. The HD Graphics model are notorious for being, good..

This can't be done to a model 2, it has a cloned 2612, not even a YM model, and it's in the 315 chip..

Does it use the same clock?
Theoretically, even if it's a combined IC, as long as it takes in the same data and clock input, the same idea applies.

In fact, the same clock input is bveing shared between multiple functions.
Any time you split an electrical signal, it's strength is halfed.

Does the 315 have an internal clock? Because if not, I don't see why it's not possible or advisable.

[evildragon]

i do think the 315 has an internal clock.. because the only crystal on the genesis 2, goes to the CPU..

[evildragon]

UPDATE: After reviewing the schematics to the Genesis model 1 (a generic schematic), I noticed something interesting, and it also is confirmed, by reading about the HD Graphics model's RF output...

The RF output on the Genesis one, also gets it's clock, from the SAME crystal that is powering the 68K, and the YM2612.. Right there I believe is the SNR loss, and why an isolated crystal helped it dramatically.. It's the damned RF modulator..

Also worth mentioning, the RF output on the HD Graphics models, is MUCH better, than that of the weaker model 1's...

So, my new theory, is that the cheeper model does indeed have a weak crystal, along with the power sucking moto chip (some cheep model 1's don't have a moto, but an hitachi, those i don't have), leave the crystal very weakened, and can't power the 2612 and the RF modulator...

So, my wonder, and I don't want to do this, as I USE my RF modulator (AND composite output), is, if maybe the RF modulator got removed right off the circuit board, maybe the YM2612 will ALSO get cleaner audio..

Like I said, I don't want to do that, as I use the RF out.. So anyone who doesn't use it, and is willing to completely trash the modulator, please record BEFORE and AFTER samples, of the same sound sample... I would like to see the improvements this causes..

[xbrinkx]

Interesting...have you thought about doing the s-video mod on your system? If you do it, you can do away with using the RF modulator and have a much better picture and see if it makes a difference in the sound quality.