Genesis Plus GX, Where is the Audio Lowpass Filter?

DAC quantization is for Mame core only.
All the Nuked cores have all the proper emulation of the electronics already.

1 Like

So with the most recent core update, there are now 3 different nuked soundcores (ym2612; asic ym3438; discrete ym3438) Which one is the one to go for most authentic model 1 sound?

Three posts above I answered just that…

1 Like

Thanks. So what are the two others for then?

Discrete YM2612 appeared on all Model 1 except the badly distorted VA7.

ASIC YM3438 was integrated into the main chip on the majority of Model 2 except VA2 and VA2.3 which had Discrete YM2612 like Model 1.

YM3438 has better DACs and sounds cleaner with less ‘ladder effect’ (google it) distortion and noise than YM2612.
BUT, some games actually use the YM2612 ‘ladder effect’ noise to their advantage therefor sound more correct on the 2612 than on the 3438.

Discrete YM3438 never appeared in any Genesis console but it sounds similar to the ASIC YM3438 and can be installed in a Model1.

Mame core is the most pristine sounding with no emulation of the ladder effect distortion, and no DAC Quantization (if Off), it is a pure FM synthesizer.
This option is actually what Sega engineers would have preferred but had to live with the distorted and noisy real hardware. :smile:

You can clearly hear the difference in Contra: Hard Corpse, in the Music Test menu play “Konami Music”, it is clearly audible on the polyphony of bells.

4 Likes

Hellfire is the best example of sound difference. Jump straight to 5:28 and 12:32 to compare.

UPD: I wonder if there any game that actually leverage YM3438 chip? Maybe some kind of list of such games exists?

2 Likes

Holy shit, I’ve seriously never been able to tell the difference. Those timestamps were way useful.

If nothing else the speed of how the sound is handled on the Model 2 sounds horrendous compared to the Model 1 here.

1 Like

Oh man, wish I had found this thread earlier… nice development on the YM2612 btw!

I’ll have to try it out. Right now RYMCast has set the benchmark as far as accuracy goes, I’ll see how this new core fares.

Can the setting for Model 1 sound be Mono instead of Stereo?

So did the Nuked core get removed or is it default now? I have the latest core and no audio core options are available.

It’s there. In quick menu > options, go down to Mega Drive / Genesis FM and scroll until you see ‘nuked (ym2612)’

I don’t have it. Retroarch 1.7.6 Win 7 x64, core version 1.7.4 997360b.

There is Master System FM but nothing else labelled anything like Mega Drive / Genesis FM.

Looks like your core might be out of date. What platform?

I listed my platform and all version numbers above. I just used Core Updater today and this is the core I got. What version number core are you on?

You can see my version, f5eed51, in the image. It’s the most recent version, last built on Feb. 2, it looks like.

Can you try deleting the core manually from the cores folder and re-download?

I deleted the core and redownloaded from the page you linked and I still get the same thing. What the hell?

Are you loading from a playlist? If so, is it possible you have an old copy of the core lying around somewhere that the playlist is linked to?

1 Like

You were right, @hunterk… I had no idea that an absolute core path (not relative) was stored in the playlist. Thanks for the heads-up! All is fine now.

2 Likes

Audio filter enables the low pass filter. Low pass filter % tunes the amount of filtering. A real megadrive console had a low pass filter on the audio so without it the audio is not correct but it does use up extra resources.

Which is correct to match the Model 1 Genesis, Low-Pass at 40%, 45% or 55%? It seems as if at one point you said 40%, then 45%, then at another time you said 55%.

I just noticed that this still occurs in the latest Genesis Plus GX core. The Sega CD PCM Chip’s output is also filtered leading to really muffled Red Book audio if the low pass filtering is enabled.

Of course disabling Low Pass Filtering will cause all FM Sound to be harsh and inaccurate so that’s not a solution.

Any chance of a fix for this?

Update:

I reported this behavior as a bug on the Genesis Plus Gx core GitHub and this is what ekeeke had to say,

" CD audio (CDDA + PCM) is indeed first mixed to MD audio (FM + PSG) then low-pass filtering is applied on the mixed stream, just like it is done on real MD hardware when you get the audio from the console A/V ouput.

You could however also get the audio from the CD unit L/R stereo outputs (using a cable connected to MD mini-jack output), in which case MD low-pass filtering only applies to MD audio, which is then mixed to CD audio in the CD unit.

Note that there is still low-pass filtering applied in the CD unit, just less stronger (there is a first low-pass filter on PCM and a second one at ~20KHz on the mixed audio stream before it goes out from L/R outputs).

Anyway, this is currently not emulated because it is more complex (the emulator and the library it uses for resampling is not really designed to apply mixing and filtering at different stages) and less optimized regarding CPU processing.

I left this issue open though as it would indeed be nice to have this option."

3 Likes