Bad audio quality through SCART from Genesis (using headphone out) – OSSC 1.6

[James-F]

@BuckoA51 you might want to edit that out about the 1k resistors., it’s not an accurate advice.
I have a VA5, and 1k resistors as load fixed noise issues, but I have not mentioned VA0 and VA1 anywhere.
VA0 and VA1 JAP Model 1 have distortion because of higher op-amp gain, and have nothing to do with the OSSC or load.

[BuckoA51]

I’m lost then sorry. Adding those resistors to my VA5 did absolutely nothing.

What then is the fix for VA0 and VA1?

[Damn-Deal-Done]

The noise in question this thread is about is digital noise. We should keep it about that. The problem with overly loud sound and amp distortion is something else.

The noise i describe sounds like digital conversion errors.

If there is inherent distortion coming from the megadrive as part of the console’s crap design, it needs to be represented accurately by the OSSC. Which it isn’t at the moment.

Overly loud and distorted megadrives is a common problem which i don’t think is the responsibility of OSSC designers.

Accurate ADC conversion is, warts and all.

Looking forward to the firmware to see if it fixes the digital chirping and artefacts.

[Zoomer88]

I couldn’t have said better. That’s why I’ve created this topic. It’s not about Megaeverdrive (genesis) deficiencies rather about OSSC problems. I’m happy about that it could be solved by firmware, can’t test it right now though.

Great job anyways!

[BuckoA51]

Whatever is causing audio issues needs to be documented and fixed. The firmware fix will fix the issue on most Megadrives, but we should equally document the correct fix for the unique issues that VA0/VA1 units have too.

[James-F]

Sega-16 has PLENTY info about that and million other sega related topics and modifications,, a quick search there will yield lots of results.

Here is the gain fix for Moddel 1 VA0-VA2:
http://www.sega-16.com/forum/showthread.php?27397-VA2-Preamp-fix

[James]

As far as I can tell that Sega-16 link is a discussion about that mod not working and the audio being too quiet. I think they eventually figure it out but I couldn’t follow it.

I have a VA1 JP Megadrive that I’d love to fix the preamp distortion issue on but I can’t find an easy to follow guide anywhere (Sega-16 included)

Can anybody help?

[James-F]

What you don’t understand?
First post first image.
Change the 47k resistors to 10k resistors, and change the caps to 4.7nF.

Post #75: http://www.sega-16.com/forum/showthread.php?27397-VA2-Preamp-fix&p=726935&viewfull=1#post726935
Change the 33k to 20k to boost the volume after the mod to VA3-6 level.

Complete gain + volume fix for Model1 VA0-2:

[James]

That’s awesome thanks! I couldn’t view the image in post #75 as my login has been awaiting acceptance sine Dec.

Now just to summon the courage to tackle those SMD components unless you wanna offer it as a service bucko?

Thanks again

[Damn-Deal-Done]

I can confirm that the update has fixed the digital noise on my VA1 NTSC-J Mega Drive. So cheers to the devs.

I believe in some cases the digital noise might be masked by the console’s distortion, so some people may be unaware it exists at all. If you know what you are listening for it is obvious though. Especially when in my case the noise was not perfectly uniform across the stereo as per one of the audio examples pages back.

The update has cleared the noise up completely so now I only hear the true distortion generated within the Mega Drive itself but only on some games. But this distortion is noise free now.

If anyone needs a good example of a loud, distorted game for testing their audio mods I suggest ‘Rolo To The Rescue’. It is a very loud game. The most distorted I have come across so far.

[dafoomie]

The update definitely resolved the issue on my VA6. Much appreciated.

[James]

Thanks again @JamesF for your help with the audio distortion. Finally summed up the courage to tackle those SMD caps and resistors (turned out to be no big deal) on my JP VA1 MD and now the distortion is totally gone with no change to tone or volume. It sounds freaking amazing ?

[slickrasta]

I had buzzing and audio distortion of all sorts literally making my Genesis unplayable until I bought a quality properly shielded RGB SCART cable the one you linked to is almost definitely the same crappy China made one I had issues with that I bought off eBay for a similar price. The good one I got in the mail just today is a packapunch cable from retro gaming cables. My money is that is your issue. I even bought new old stock replacement power supply as I had read that could be the problem but was proven wrong when I tested it out with no change. Flawless through the good SCART cable now though!

[accaris]

I have to admit I actually went out and bought a new Sega Genesis to fix this issue, which I assumed was caused by my using a VA6, and I ALMOST bought a new SCART cable while I was at it. The high pitched ringing/chirping was VERY noticeable in Shining Force, especially during the town music, and I never would have assumed it was a digital issue.

I updated my firmware to .81 and the problem was immediately resolved.

[Author]

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