VOGONS


First post, by MaxWar

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Alright folks, the time has come to reveal the data acquired from the audio blind test experiment that was started a week ago.

As the title implies, the subject of this study was:
Discrete Vs. Integrated YM3438.
Vs_zps65f39d49.png

The goal was to evaluate if these two chips sound significantly different from each other and if so, which one was preferred.
I wrote a load of details and explanations so most questions you might have about the test are likely explained down there.
I also added lots of pictures so hopefully its a good read and you do not get that TL;DR feeling. But if you still do, you can skip right to the results and conclusion, I guess...

Background Information:

On the original Sega genesis model 1, the FM audio chip is the Yamaha YM2612. This is a digital FM synthesizer with an integrated DAC ( digital to analog converter). This DAC was the main flaw of this chip as it introduced a lot of noisy artifacts during the conversion.
P1010561_zps3a0fd5aa.jpg

Yamaha then developed the YM3438, which is basically a CMOS version of the YM2612 but they also improved the DAC. This new DAC greatly reduced the amount of processing noise/aliasing in the sound.
P1010559_zps04bbb4bb.jpg

The stand alone YM3438 chip ( or discrete ) seen above was never used in a Sega genesis console however. Instead Sega integrated the new YM3438 FM synthesizer inside a large general purpose ASIC, the FC1004. This chip was used in the model 1 VA7 and model 2 VA0, VA1 and VA1.8 revisions of the genesis console.
P1010438_zpsbeba723e.jpg

Now the interesting part is that supposedly, the DAC was even further improved in this model and it removed the Bit depth truncation associated with the Ym2612 and Ym3438. You can read about this on wiki: http://en.wikipedia.org/wiki/Yamaha_YM2612. So basically this would mean that the Sega Integrated YM3438 (FC1004) is the best version of the 3438 ever made. At least according to the literature.

The Crystal Clear audio mod. (CCAM)

Ok So basically the best version of the FM chip is inside the early model 2 consoles, which ironically are renowned for having the worse sound!
The horrible quality of the sound however has nothing to do with the chip but rather with the lackluster amplification circuit Sega used in those consoles.
This is what Tiido Priimägi wanted to fix when he started developing the Crystal clear audio mod years ago. I am sure most of you have at least heard about this mod. It is a pretty complex mod so only few people as of now benefit from it. Basically it takes your crappy early model 2 and turns it into the best sounding Sega Genesis possible. But you need to build this circuit first.
CCAM1.png

The important detail is that this circuit only works with the YM3438 ( ASIC YM2612 as Tiido put it back then), and not the discrete YM2612 of the model 1. The reason for this is that they have different type of outputs ( YM3438 is louder ). As a result this circuit was only to be used on model 2 consoles and did not work on model 1 consoles ( except VA7, which is basically a Model 2 in model 1 case ). This was not considered a major problem because the model 1 already had a decent amplification circuit. However those looking for the ultimate audio for the genesis would get a model 2 and a CCAM as this setup is much better than a stock model 1.

As of now there are no CCAM equivalent for the Model 1. While the amp in the model 1 is already pretty good, the main reason to this is that the YM2612 was considered inferior so most modders did not consider it worth the bother to develop a better amp for it.

Now what if we swap the YM2612 in the Model1 for a YM3438?
The two chips are pin compatible so in theory it is pretty simple to remove the YM2612 in a model 1 and install a YM3438 instead. But remember that the two versions of the chip output differently so If you simply swap them over your genesis 1 will output garbage as sound. The genesis 1 onboard amp is inadequate for the 3438.

AFAIK this problem had not really been assessed and documented until earlier this year when a few modders, EvilDragon and Drakon among possibly others got in their mind to make this work. This concluded with a YM3438 working in a genesis 1 using a modified model 1 amplifier.

While this experiment was successful in the end it mostly went under the radar and was seen as a curiosity rather than something actually useful. One of the main reason for this is that it was assumed that the Discrete YM3438 was significantly inferior to the YM3438 that is integrated in the model 2 genesis. In other words the the stand-alone discrete YM3438 was seen as pretty much an equivalent of the YM2612 while the true superior chip was the FC1004 found in the model 2.

This is where I came in and repeated that experiment myself. However instead of using a modified model 1 amplifier on the discrete YM3438 I used the CCAM amp. It immediately struck me that the discrete YM3438 was being underrated and in fact was much more similar to the integrated YM3438 than was popularly admitted.

I also knew that simply saying so would be seen as: "well, thats just your opinion" and that this would be lost in the immensity of the internet all the while people would continue to occasionally speculate about it.

So i went a bit nut and decided to make this a big deal and do this blind test experiment to once and for all go to the bottom of the question and substitute all the talk by actual facts!

The blind test and comparative recording methodology.

I do have some experience in comparative recording methodology. Actually, as far as i know, no one in the retro gaming/modding scene went as far as I did in perfectionism regarding to this. What I am doing is more akin to what is found in the professional audio industry and among hardcore audiophiles rather than the retrogaming circles.

I wrote a precise protocol for this, which I used before for comparing different sound cards, different Famicoms and even the impact of recapping systems on sound quality. Most of this protocol can be found here https://sites.google.com/site/soundcardcompar … ecording-method. I will answers questions about it if need be.

To sum it up the basic idea of the comparative recording recording methodology is to limit all external sources of variation as much as possible and leave what you want to compare as the only significant source of variation. Its pretty straightforward really.

Details on the hardware setups I used.

For this blind test experiment I had two consoles.

The first one is a standard Genesis model 2 VA1 with CCAM amplifer.
The second one is a Model 1 VA3 with its YM2612 chip replaced by a YM3438 and also uses the CCAM amplifier.

Both are recorded into audacity using the exact same presets and recording hardware and I used the very same CCAM circuit on both machines.
My CCAM circuit was made by RetroGamer343 from Sega16 and I modified it to have very little LowPass filtering, according to the original Tiido schematics.

Typically a CCAM amp is permanently installed into a console. However I wanted to use the very same circuit on several consoles so I made a modular setup.
Here you can see I mounted the CCAM PCB inside of a grounded tuna can which serves as a complete RF shield for the circuit. I installed RCA connectors on it, one side connects directly to the chip and the other side connects to the recording device.
P1010463_zps7d5308ed.jpg
P1010465_zps1fc45dad.jpg

On the consoles side, all preparation was made in a consistent manner. The chip outputs were completely isolated from the motherboard either by cutting traces or removing components. The chip output was then connected directly to the CCAM and nothing else via fully grounded shielded cables.

Here is a close view of the connections on the Model 2 VA1.
P1010428_zps3d86fb1b.jpg

Here you can see that the YM3438 in my model 1 is installed in a socket and similarly connected with shielded cables. The PSG here is tapped on the underside of the board, unseen in this picture.
P1010563_zps055858a8.jpg

Here is a view of the complete model 1 setup just prior to recording.
P1010564_zps9704463e.jpg

Blind test results:

First I will declare that these results are real and I did not falsify or modify any of the numbers. These are exactly what I received from the participants. While I think it is better to keep the choices and identity of indivitual participants anonymous, I still stand behind this data and rest my reputation and credibility on it as I know this is 100% genuine. If need be all the PMs I received could be verified by a third party and the data double checked. Furthermore, I encourage participants to discuss their experience in the thread now that the results are in.
-----------------------------------

In total 30 people from across 5 forums participated in this blind test spanning a period of 1 week.
This is slightly more than I was initially hoping for so I am happy with this number.

As you now know the two console were a Genesis 2 VA1 with CCAM and a GENESIS 1 with discrete YM3438 + CCAM.

The Model 2 VA1 recordings were respectively:

CONTRA-A D&D-B SONIC-A ThunderForce-B Turrican-B […]
Show full quote

CONTRA-A
D&D-B
SONIC-A
ThunderForce-B
Turrican-B

By logical opposition the YM3438 Modified model 1 were

CONTRA-B D&D-A SONIC-B ThunderForce-A Turrican-A […]
Show full quote

CONTRA-B
D&D-A
SONIC-B
ThunderForce-A
Turrican-A

So for those who made the test, I guess you can now compare with your results and see where you are at 😀

The rundown:

As i said, a total of 30 people made the test.

-8 out of 30 people said they could not make any difference at all and responded "no opinion" for all the music pairs.

-7 out of 30 people gave a clear response for all the pairs.

-15 out 30 people responded "no opinion" for at least one or more of the pairs.

Contra results.

-10 out of 30 people had an no opinion on this one.
-12 out of 30 preferred the Integrated YM3438 version (Contra-A)
-8 out of 30 preferred the Stand-alone YM3438 version (Contra-B)

Dungeon&Dragons results:

-14 out of 30 people had no opinion on this one
-4 out of 30 preferred the Integrated YM3438 version (D&D-B)
-12 out of 30 preferred the Stand-alone YM3438 version (D&D-A)

Sonic 2 results:

-15 out of 30 people had no opinion on this one
-3 out of 30 preferred the Integrated YM3438 version (Sonic-A)
-12 out of 30 preferred the Stand-alone YM3438 version (Sonic-B)

ThunderForce IV results

-13 out of 30 people had no opinion on this one
-8 out of 30 preferred the Integrated YM3438 version (ThunderForce-B)
-9 out of 30 preferred the Stand-alone YM3438 version (ThunderForce-A)

Mega - Turrican results:

-12 out of 30 people had no opinion on this one
-8 out of 30 preferred the Integrated YM3438 version (Turrican-B)
-10 out of 30 preferred the Stand-alone YM3438 version (Turrican-A)

Mean total results:

Each participant evaluated 5 samples and we had 30 participants so that makes a total of 150 samples.

-64 out of 150 samples received a "no opinon" verdict.

-35 out of 150 samples favored the model 2 with Integrated YM3438

-51 out of 150 samples favored the model 1 with Discrete YM3438

graph_zps561798bb.jpg

Conclusion:

It was observed through this test that when people were asked to blindly chose between the two choices, they would not find any detectable differences 42% of the times. By opposition when they did make a choice between one or the other, they were just as likely to prefer one or the other. I therefore conclude that for the average user, there would be no significant perceptible difference in using one chip or the other. This can be concluded with an acceptable degree of certitude considering the size of the sampling pool and the distribution of the data.

The practical conclusion of this is that we can assume that the highest sound quality on a genesis is also achievable on a Model 1 machine and not only on the model 2. High quality CCAM audio is no longer something that should be associated strictly with a Model 2. The stand-alone YM3438 chip is just as capable of delivering quality sound as the integrated one.

Possible Caveats

Now this test was limited to a subjective appreciation of musical samples. There are other potential aspects that could complicate the application of the results.

- Wild discrete YM3438 chips not being all created equal: The only way to get these chips in the wild is mostly by ordering them from Chinese part distributors. There is always a possibility of bad batches or bootleg chips being in circulation. I made this test using 1 single chip that I evaluated was a good genuine specimen. While it seems that in my case it turned out very well, there is no data on the reliability of finding these chips in the wild.

-Compatibility issues: My personal experience with the discrete YM3438 was of 100% compatibility in all the games I tried, but this is no more than a dozen games. There are reports of timing incompatibility issues in other games using this chip.
So far issues have been reported in:
-Sonic Spinball.
-Earth worm jim.
-Super fantasy zone.

I am now awaiting to receive a copy of Sonic Spinball to test this myself. I will update this page with my findings.
The good news is that it is possibly a fixable issue but that would make the implantation of the genesis 1 modification even more complicated than it already is.

A few last words

Firstly, once more, thank you to all who contributed with their inputs 😀

In the end it is less complicated to use a CCAM on a model 2, but the adventurous modder who prefers model 1 for whatever reason now has an option to get that nice CCAM sound on a model 1, with no compromise on the sound quality.

Personally I prefer using a discrete YM3438 on a model 1 if only because there are interferences issues on the FC1004 based model 2. This will produce a characteristic buzzing noise that modulates along the activity of the console. This can be heard as a buzz in the beginning of the D&D song included in this test package. A handful of people made mention of it but no more. This is a consequence of the Model 2 ASIC/board layout and the discrete implementation on a model 1 does not suffer from this.

HOWEVER, there is a later version of the Genesis Asic, also known as the GOAC ( genesis on a chip ) which basically integrates everything on the console in a single chip. The integrated 3438 on these does not suffer from noise issues. In fact they have the cleanest output of all the genesis consoles. These can be found exclusively on Model 2 VA4 and Genesis model 3 consoles.
They however have an altered/wrong sound balance between FM and PSG so implementing the CCAM on those requires a little fix.

Edit: Also, sorry in advance if I forgot to mention a relevant link or to name a relevant person in the post. I will add details, references, links and answer question on request.

*********************************************Original Post*********************************
Hey there guys, you know how I like audio comparisons right? :p
Here I have a blind test for you, which of course is a load of fun to do :p

I have a zip file containing audio files in flac format. The download is about 110mb. ( 3 mirrors ) MEGA seems fastest.

https://mega.co.nz/#!WVRnTbaR!IEf8_Gdco3QEu34 … FeQ0TcSleiF6wlM

https://docs.google.com/file/d/0BzsnL20-4a37Z … dit?usp=sharing

http://www.mediafire.com/download/35s2xbs8421 … isBlindTest.zip
They are songs recorded directly from two mystery Sega genesis consoles.
There are 5 songs each recorded twice, for a total of 10 files.
Each version of the song has the suffix A or B, which was assigned randomly and doesn't mean anything.
The date of all files was also reset so you cannot know in what order they have been recorded.

The goal is to listen to each files and state your opinion on which one of each pairs sounds better, or what your favourite is.
If you cannot hear any difference or don't have an opinion just say 'no opinion', this is still a valid response to this test.
Alternatively you could also have opinion on only one pair but not the others.

When you respond, just make a short list of your 5 favorite picks. Something like this for example:

Song1-b Song2-a Song3-b Song4-a Song5-b […]
Show full quote

Song1-b
Song2-a
Song3-b
Song4-a
Song5-b

IMPORTANT! Respond by PM to me!!

Plz do not respond in the thread!!! Your responses might influence others!!
I am trying to keep this as scientific as possible. Please use PM.

I will publish the results and explain what each file was when I have enough responses to have a statistically valid sample.
This will be posted in more than one place, to get more participants.
Thanks in advance!

Last edited by MaxWar on 2013-08-04, 04:43. Edited 5 times in total.

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Reply 1 of 17, by badmojo

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PM sent.

I just bought me a Mega Drive, as they're call here, so am looking forward to hearing more about this. I tried to research which model to get before I bought one but there are too many versions, so in the end I just found a cheap "Mega Drive 1" and will suck it and see. I chose it because it had "high definition graphics" on it, which sounded like something I needed 😀

Life? Don't talk to me about life.

Reply 2 of 17, by MaxWar

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Way to go man, you can't go wrong with a high definition model 1.

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Reply 3 of 17, by Stull

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PM sent!

Reply 4 of 17, by F2bnp

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PM sent!

Reply 5 of 17, by SquallStrife

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I was dis-satisfied with the audio from my Mega Drive 2, so I bought a Mega Drive 1 in Japan. Gogo universal cartridge slot! 😀

Downloading the file now.

VogonsDrivers.com | Link | News Thread

Reply 6 of 17, by MaxWar

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23 people participated so far, I will publish all the details Saturday around 19:00 ( GMT-5 )

For those would still like to do the test, you have less than 36 hours to do so 😀

FM sound card comparison on a Grand Scale!!
The Grand OPL3 Comparison Run.

Reply 7 of 17, by Gemini000

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This intrigues me since I have three NES' and one of them actually sounds different than the other two, as though one of the sine wave generators isn't working properly as it decays notes faster than it should. I might actually be able to tell what's going on with the audio processing if the comparisons sound different and provide that information to you in the PM I send. (Presuming you don't already know what's up. ;)

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Reply 8 of 17, by MaxWar

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Thanks Gemini. I am very intrigued by that NES system. Maybe there is a glitch in the sound processor?

FM sound card comparison on a Grand Scale!!
The Grand OPL3 Comparison Run.

Reply 9 of 17, by Gemini000

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MaxWar wrote:

Thanks Gemini. I am very intrigued by that NES system. Maybe there is a glitch in the sound processor?

I'm actually guessing one of the capacitors on the particular sine wave generator is the problem, though to be honest, I don't know enough about the internals of the NES to know for certain. It's an old system that belonged to my brother-in-law and never saw much use. (He had sucky games. :P )

--- Kris Asick (Gemini)
--- Pixelmusement Website: www.pixelships.com
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Reply 10 of 17, by MaxWar

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The two square wave signals are mixed together right inside the processor so if it affects only 1, it might sounds more like a fault in the IC.
Anyway I would still be curious to hear how that actually sounds, If you ever have a mind to record the effect :p

When you compare the NES to various Famicom versions, there is an audible difference though. Mostly to do with the level of low pass filtering. I made a comparative test of this last year.
You can get samples there if you are ever curious.
http://www.famicomworld.com/forum/index.php?topic=8630.0

FM sound card comparison on a Grand Scale!!
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Reply 11 of 17, by MaxWar

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Results are in guys, I edited the first post.

FM sound card comparison on a Grand Scale!!
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Reply 12 of 17, by Stull

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Nice work; this was a cool experiment. Evidently I chose the Model 1 for 2/5, the Model 2 for 2/5, and was uncertain on the remaining 1/5. 😉

Reply 13 of 17, by MaxWar

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Thanks 😀 Actually, no one in the 30 people made a 100% polarized choice. The most extreme case was 4/5 in favor of one chip.
Also, I noticed my links were messed up due to the forum where I pasted this from had different URL coding, fixed now 😀

I realize this experiment is in truth only significant for a handful of hardcore modders, but I hope the participants who made the test all had at least some fun doing the experiment, even if most of them will likely never do these mods.

FM sound card comparison on a Grand Scale!!
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Reply 14 of 17, by SquallStrife

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Good show! 😀

This was sorta the result I expected. My judgements all ended up being based on how audible the noise floor was, since I couldn't detect any other difference.

I think, in essence, your conclusion is correct, MaxWar. Once you remove the output stage as a differentiating factor, the difference is too subtle to really notice for most people on most listening equipment. IMO the biggest reason to build the CCAM, is the god-awful output stage on late model Mega Drive 2's, with the obvious distortion and clipping problems.

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Reply 15 of 17, by Gemini000

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All 4 of the songs I voted to be better came from the Model 1! :D

*hugs Model 1 Genesis* ^_^

I was being super-analytical about it too, going so far as to placing the waveforms perfectly side-by-side in my audio editor and inversing the waveform of one so I could listen specifically to the differences between the two. The only song I couldn't make an opinion about was the one from Thunder Force IV.

Oddly enough, I thought all of the A files all belonged to one Genesis and the B files all belonged to another, since there seemed to be some commonality despite being from different Genesis units. For instance, the percussion in the A files in general seemed to be stronger.

Everything said though, these differences were, for the most part, REALLY tiny. With every song I had to listen to parts over and over and compare specific sections together multiple times to figure out which ones I preferred, so under normal circumstances, the average person would likely never be able to notice or care. :P

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Reply 16 of 17, by MaxWar

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SquallStrife wrote:

Good show! 😀
IMO the biggest reason to build the CCAM, is the god-awful output stage on late model Mega Drive 2's, with the obvious distortion and clipping problems.

Yes, however if you compare CCAM and stock model 1, I still prefer the CCAM. It is much cleaner and restores the high frequencies. You also do not get those nasty DAC artifacts of the YM2612.
I have an ongoing project to make a big database of genesis recordings to compare all major mods and hardware variation. You can get my Stock model 1 recordings there.
http://www.sega-16.com/forum/showthread.php?2 … s-mods-and-more
Other people are right now working on even more alternative amps circuits for the genesis ( 2013 is a very good year for genesis audio modding it seems, someone even installed a YM2612 in a early model 2 recently lulz )

I will soon add the files used in the blind test to my database too. However I need to invert the stereo first...
I actually made a mistake when recording for the blind test and the stereo is reversed in all the files, no one seems to have noticed so far... 😊
I was halfway through the recording session when I realized L and R were inverted and just kept going as this was not relevant to the test if all is consistant.
But I will set this straight so the archive as a whole is consistent.

Gemini000 wrote:
All 4 of the songs I voted to be better came from the Model 1! :D […]
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All 4 of the songs I voted to be better came from the Model 1! 😁

*hugs Model 1 Genesis* 😄

I was being super-analytical about it too, going so far as to placing the waveforms perfectly side-by-side in my audio editor and inversing the waveform of one so I could listen specifically to the differences between the two. The only song I couldn't make an opinion about was the one from Thunder Force IV.

Oddly enough, I thought all of the A files all belonged to one Genesis and the B files all belonged to another, since there seemed to be some commonality despite being from different Genesis units. For instance, the percussion in the A files in general seemed to be stronger.

Everything said though, these differences were, for the most part, REALLY tiny. With every song I had to listen to parts over and over and compare specific sections together multiple times to figure out which ones I preferred, so under normal circumstances, the average person would likely never be able to notice or care. 😜

Haha, yeah you and another guy chose the discrete chip 4/5 times, and the other guy also wrote me a whole page of analysis about it.
Ironically the Integrated version is supposed to be the better version, according to literature. However in truth the Integrated version in early model 2 has higher background noise level.

This is an aspect I did not bring up until the very end of the post. The VDP noise of the Integrated ASIC in the model 2 is an issue. This is what makes the buzzing sound at the beginning of the D&D song.
This is most significantly heard on soft music parts or silence background. I deliberately avoided most of those in the test because I knew it would have given an unfair advantage to the discrete version.
But even then this background noise is possibly what explains why the discrete version was overall preferred ( 35 vs 51 ). If you isolate only the D&D sample and the Sonic 2 sample, the discrete version has a clear advantage.

What is interesting is that those two songs are pretty quiet. The recordings all seems pretty equal in volume but I adjusted the levels. In actual truth some genesis games will make much louder audio than others. For instance Contra is pretty loud! But sonic 2 and D&D especially are quiet, so I need to boost the recording volume which in turn makes the background noise more apparent. So this maybe explains why these two seem to be favored on the discrete version, at least in appearance.
This being said, for the life of me I cannot blind test the Sonic2 song 🤣

FM sound card comparison on a Grand Scale!!
The Grand OPL3 Comparison Run.

Reply 17 of 17, by dotcomrobots

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Hello,

Thanks for all your work and contribution on this, it's so cool!

I have a hard trouble finding instructions to install a discrete YM3438 on a VA3 though
Stumbled upon that dual chip solution, but I believe there is a cleaner way to do this?

Found the Drakon video too but there are no explanations on the process whatsoever..

@MaxWar if you have any instructions about this process please share it 😀