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Modded soundtrack rips and other thoughts:
#1
This may be a TL,DR for many people, but I wanted to share my own thoughts, opinions, and experience with ripping Genesis/Mega Drive music with best possible sound:


Chapter 1: Using VGM player in a flash cart:

So I started off using VGM player (the black screen with the dead fish) to play back tracks on the Genesis, but found there were minor timing issues and occasional glitches. I enlisted the help of other audiophiles in the MDFourier Discord to get to the bottom this, and we determined the actual extraction method just isn't the same as getting the original code from the game. I recall the only VGM extraction method was to use Kega Fusion's logging system, but whenever we ported that to the player in the Genesis, there would be the aforementioned slight timing issues with little pops and clicks here and there. So it's not quite the same as an ideal scenario where you would hack the game down to just the music code itself with a basic black screen and track select. Thus, preventing any logging interpretation that gets shifted into a set frame rate of I believe 60Hz. Xeno Crisis is an example of a game where it already has slight execution errors because it was ported from VGM tracks logged via Defflemask Tracker. The OST executes drum beats perfectly, but the actual physical copy of the game has random pitch/timing mismatches on drumbeats. This can especially be heard in track 7 "Forest (Area 5)" during the fast beat build-up. Here's my own recording of that using my Double Mega + Mini Mega-modded VA2 with twisted-pair wired RCA jacks:

M1 Double Mega + Mini Mega - Xeno Crisis - 07 - Forest (Area 5)

If you listen closely, you can hear a couple of the beats are off pitch. This doesn't happen in the OST. I think it's because they ported the Defflemask Tracker renditions into the game code, and the timing mistmatch causes that to happen.

Thankfully it seems a new player was coded to get around this timing issue as addressed here:

Custom VGM Player Updated

I will be very interested in trying this new player out myself to see if it improves on the pops and clicks I occasionally hear in VGM rips played via the Mega Everdrive Pro I have. More to come on that after I run some tests with it.



Chapter 2: Just how much resolution do you need for lossless archival recordings?

This was another subject I spent many hours reading various scientific articles on when doing searches in Google. In every case, 192kHz was considered a complete waste of space. Many devices only 'fake' handling that much detail to begin with. Additionally, 24-bit is totally unnecessary as well. 16-bit is more than sufficient for archival purposes (according to the articles I read). The only grey area is 96kHz. You would need something with frequencies beyond 20kHz to be worth considering it, but stock Genesis/Mega Drive audio happens to be SEVERELY low-pass filtered, with the corner cutoff at around 4kHz. This means by the time you even get to 20kHz, the audio is probably down to -90 dB, which is the same as muted. In reality for stock recordings in archival quality, 16-bit with 48kHz is perfectly sufficient. I know people feel better using 96kHz, so I really won't press that as something to seriously consider, but the 24-bit setting is total overkill. Use 16-bit, and if you really want to, 96kHz. Just know that nobody will be able to tell the difference between 48kHz and 96kHz on these severely low-pass-filtered stock recordings, not even with the best audiophile equipment in the world.


Chapter 3: Can we do better than the stock circuit in the Genesis/Mega Drive?

Absolutely! Ace's Mega Amp is a prime example of a much cleaner schematic that directly lends itself to a much lower noise floor when properly implemented in PCB mod work. My own M1 Mini Mega is a stripped down version of Ace's design that gets rid of the mono audio circuit and strictly deals with just the stereo mixing and amplifying the output. I spent 3 years testing revision after revision, determining where you needed electrolytic caps and where it didn't matter, resulting in this little board:

[Image: Rev_5_Mini_Mega_Assembled.jpg]

Further testing on installation methods revealed we get the cleanest possible noise floor by tapping directly into the voltage regulator, which can be see below in my install with twisted pair rear RCA jack wiring:

[Image: Mini_Mega_Install_Process.jpg]

This alone by itself, BLOWS away the stock audio circuit of the Genesis/Mega Drive for archival recording purposes. And you get the extra benefit of controlling how much LPF is applied. If you want stock, you can set the filtering caps to a pF rating that matches stock filtering. But we can do even better...


Chapter 4: Turning the M1 Genesis/Mega Drive into a CD-quality sound station!

My nest step was to develop a toggling board that allows both YM2612 and the much cleaner-sounding discrete YM3438 chip (used in Sega arcade hardware). This took a couple of years to perfect as well, due to the original design concepts floating around on the internet using incorrect attenuation circuitry for each chip. Additionally, the routing was so complex as to require using a 4-layer PCB, and then compact it as much as possible to reduce production costs (without sacrificing any quality in the process). I went through several revisions before landing on my masterpiece design:

[Image: M1_Double_Mega_Final_01.jpg]

Assembled below with dual-wipe sockets and additional heat sink for the YM2612 (due to using HMOS tech that gets really hot under load, while the YM3438 uses CMOS tech that doesn't even get warm under load):

[Image: M1_Double_Mega_Final_02.jpg]

And here's the combo installed in my Genesis:

[Image: M1_Double_Mega_+_Mini_Mega.jpg]

This turns my M1 VA2 Genesis into an all-in-one sound powerhouse that can output 2612 or 3438 with a flick of the switch (which can be optionally wired to an external switch). The reason for doing this is some later revisions of the Genesis/MD (some model 2's and all Model 3's) used YM3438 sound output, and indeed later games released for the system have significantly cleaner sound through 3438 playback. It's often why you hear people make the claim that a Mega Amp'ed ASIC 3438 M2 console sounds better than an M1 console. With the Double Mega, I take the M2 console completely out of the equation, and it makes the M1 the most versatile console to use for audio modding and track ripping.

With all that done, I moved the LPF corner cutoff to 18kHz, allowing for absolutely crystal clear track rips. The Xeno Crisis example track I posted earlier is taken from this very setup. For an older classic library track, here's my own recording taken from Phelios called "Watch Dog in Hell"

Double Mega + Mini Mega - Phelios - Watch Dog in Hell

Beautifully clean and clear in my opinion.

Anyway to conclude, those are my thoughts and experiences on taking Genesis/Mega Drive audio to the extreme in terms of quality and clarity. I have since started making full soundtrack rips. If anyone is interested in trying one out to see what they think, here's Thunder Force II ripped from my setup using the menu sound select screen:

Thunder Force II - Double Mega Soundtrack

Cheers!
-FBX
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#2
Thanks for the post FBX, I really appreciate you sharing your adventure through all the madness that is related to the Mega Drive audio.

I won't go into debating the whole 96khz/24bit thing (and, for what is worth, 24-bit resolution is *way* more impactful and important than a high frequency rate), because this would quickly degenerate into a flame war with people throwing out the infamous hydrogen audio video which I'm pretty sick of by now.

The long and short of it is that depending on the ADC used, it is optimized to work at a certain frequency and you should use that, because all the others are just downsampled from the highest resolution the ADC works at.
If you were around the time when we were discussing equipment in the MDFourier Discord, you would have found proof of this (it's still there, although buried in thousands of messages).

Also, a bit of news from the last months of research: all VGMs ripped with KEGA have wrong timing. We were able to circumvent this issue because we had an adjustable VGM Player (Deadfish), but unfortunately some VGMs are just broken (wrong timing, pitch, instruments and other artifacts).

Now we have a new logger in blast'em which is 100% accurate but the whole mega drive library would need a re-rip which is a huge task.
We've also proven at this point that VGM format is accurate enough for archiving (we have a drift of <1ms each minute which is the same you'd get by recording the same track twice on the same Mega Drive from the game's sound test), we just need now a way to keep this accuracy on the hardware VGM player side (that is, the Deadfish player).

Your work is highly commendable and I absolutely back it 100%, I've been following your progress for quite a lot of time.

For what concerns us and our goals, we'll be sticking with original hardware even through all of it shortcomings because that's our mission, but I wouldn't hesitate to recommend your work to anyone who's looking forward getting rid of all the issues inherent with the original hardware but keeping the same sound signature.

Thanks again for your post, I really appreciate it Smile
Vi veri veniversum vivus vici
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