Awesome thread, thanks for posting!

something else to add - here's how to read and understand the serial numbers on the bottom of model one's.

the first digit of the serial number identifies what factory produced that particular genesis. i know at 3 is taiwan and i assume 1 must be japan but i'm not sure of that.

the second digit is the year it was made. 9 means 1989. 0 means 1990, 1 means 1991, etc.

the third digit is usually a roman numeral indicating which production run produced this.

the rest of the numbers is what # this was in the production run. this is either 5 or 6 digits.

someone correct me if i'm wrong but i'm pretty sure this is how it works.

Discovered this thread on google today. Occasion is that I dug out and dusted off my Genesis model 1 after becoming very dissatisfied with the genesis audio quality on my Genesis 2/SegaCD2/32X rig. Comparing the two, I did like the sound better on the Gen 1, but it still didn't seem "better enough" based on the comparo clip on the Genesis' wikipedia page. I remembered hearing that some of the very late Model 1s actually had the cheaper mixing circuit a la the model 2, but I didn't know how to tell whether I had the good one or bad one.

Soooo, I found this, read the whole thing (very informative!) also checked out the milkcrate comparo linked at the end (great sample tune!) grabbed a screwdriver and would go on to discover that my Genesis 1 contained motherboard USA VA7.....crap! :-(

Giving it a listen on my home stereo* using the headphone out on the Genesis (using a stereo mini to LR RCA cable), I do have to disagree with the assessment that VA7 is overly hissy, or lacks in bass output. It seemed fine in those respects. -However- I do notice a lot of scratchiness and flatness in the high end, no brilliance that characterizes the superior mixing hardware (per the wikipedia clip). Comparing my Genesis 1 to the wikipedia clip, my Gen 1 sounded much closer to the Gen 2 than the Gen 1 in the example, so I would agree with the overall sentiment that the VA7 does not sound particularly good.

I have a friend who has a Gen 1 with the "High Definition Graphics" decal, which this article says is a sure-bet to have the better audio circuitry...rest assured I will get to work on trying to work a trade with him post haste! :-D

Thank you for this very informative article! I've been greatly benefitted by it!

God Bless!

-J

p.s. Another important question: If I get the HDGFX branded Gen 1, hook it up to the Sega CD model 2, and the 32X, use the headphone jack from the Genesis into the Sega CD, and then then LR RCA cables from the Sega CD into the Stereo, will I still reap the benefits that the Gen 1 offers, or will the Sega CD/32X rob me of that? Lemme know! Thanks!

* =If you are interested in specifics on my stereo (the specifics of my test environment, as it were), PM me.

Been dragged to this upon opening my Genesis and finding a VA7... I find the reports on its shitty sound being truly exaggerated. Seriously, it's not THAT bad at all. I connected it yesterday to my stereo and there was NO hissing, and decent bass sound.

Sorry for the bump but I've had a few burning questions.  In the ASIC based Model 2's what causes the difference in sound quality?  Does it have to do with the signal path of the audio or the actual ASIC revisions?  I'm going to replace all the capacitors on my VA1 but for instance, would a VA1 with CCAM sound the same as a VA3?  This is good information to know, so I don't go and waste money on finding two VA3's.

i would love to hear a detailed side by side comparisons of all of the models. It would be interesting to here all the differences.

Awesome, thank you!

CCAM is for machines with Sega 315-5476, 5660, 5700 and 5708 ASICs. But it should work nicely with 315-5960, and it also works with the ASIC in VA2 Genny3, but you need 100K resistors instead of 22K ones on the FM input lines.

As long as all your transistors are equal and resistors accurate (small differences will cause distortion) then you should not get issues with sound quality. I once mixed different manufactuer transistors and had to corrigate resistor values to get both channels equal...

Well crap ha.  I bought two model 2's and neither are VA3's  One is VA1 something and the other I haven't cracked open yet.  I'll do sound comparisons, but now I'm after two VA3's.  (Hit me up )

But above it says that it depends on the revision of the Model 2. So they're not all the same ASIC revision, if you have a Model 2 VA2 and VA2.8 (apparently), they're discrete 2612s...

hmmm, my guess is that a CCAM Model 2's would all sound the same... Its the same ASIC revisions and the CCAM replaces the audio signal path, so unless the noise is caused by power or some other issues I would think the CCAM would be dandy.  I'm probably entirely wrong here though

I don't know! It'd be cool to hear if TmEE has advice on certain models for his mod.

I did some sampling from animal style's CCAM modded console, and there was unfortunately some distortion in the right audio channel. I can provide an example later tonight. I don't know if there's some weird mistake with this particular implementation of the CCAM, or if the model involved is part of the problem. I guess the next step is to find out what revision model 2 joey has, I didn't bother finding out before...

How does this correlate to TmEE's crystal audio mod? Can the "bad" PCB revisions be saved?

this is super great and concise

thank you

Excellent stuff man - I could never find a straight answer for all of the models!