Sega Genesis with a discreet 3438...yeap...it is pretty awesome!

[+-^CrossBow^-]

On both of those links you provided they only list instructions for the mega amp on model 1 va7 and model 2 systems. And the main reason for the use of the 3438 is because it incorporates a true 8-bit DAC in the chip for the PCM samples. The 2612 uses a flawed 6-bit DAC originally. Again, this was all corrected with the later models using 3438 circuits embedded in the main custom ASIC on the later units.

 

The megaamp works wonderfully for model 2 and va7 systems. But in my listening of the samples from it, it filters too much out on the HDG model 1s. That filtering does remove the noise and crackle from low quality samples, but at the expense of bass and highs on both ends of the spectrum. Besides, the noise and crackles of the samples is largely due to the samples themselves and not so much the quality of the hardware. You can only polish a turd so much...

 

For me the biggest reason I wanted to add the 3438 was for much broader stereo separation. This has the nice effect of essentially bringing out each instrument channel and at least to my ears, I can hear each instrument much more clearly than before. The percussions stand out the most of course. Again it is up to the individual and their preference. I don't care for the heavy filtering that the megaamp does on the earlier model HDG genesis units.

[uji]

I'd love to hear a before / after comparison with Sonic the Hedgehog (Any one) Best track is Hydrocity zone act 2 on sonic 3 tho

[+-^CrossBow^-]

I could have done that last week had I known, but I've now modded the other I used for the 2612 vs 3438 comparison video and it too now has a 3438 added to it. I did pick up another Genesis va6 and once I add the RCAs to it later in the week I hope, I could try and capture some then. But this other Genesis was sent to me to mod it also...so it won't have the 2612 as the output for long.

[+-^CrossBow^-]

But those boards can be used everywhere and it seems they actually bring out the very best sound on many/all the motherboard revisions.

My question then is why one would switch to the 3438 if the 2612 is doing its job and thru the MegaAmp the sound is not distorted/cut/muffled/etc...

 

To answer your question, I guess one wouldn't. However, the 2612 isn't just about the distortion and or muffled sound. Most of that has to do with the amp circuits in the genesis revisions that cause all of that. As I said before, the biggest reason to add the 3438 to the 2612 model Genesis systems is reap the benefits of the corrected circuitry within the 3438 over the 2612. Remember that starting with the va7 Sega, began using the 3438 inside of their large custom ASIC to produce the sound going forward. Largely due to the slight flaws within the original 2612 chips. And again, if you look at the instructions etc for the MegaAmp, they are all for adding it into a va7 or Model 2 revision Genesis and not the va6.5 and below. Because again, most would agree that the MegaAmp isn't needed in the earlier model HDG Genesis units.

 

It is really personal preference honestly. I prefer the larger stereo separation of the 3438 and additional clarity I can hear from each instrument channel that the 3438 provides.

[+-^CrossBow^-]

Just finished up John "The Immortal" Hancock's model 1 Genesis with the 3438 synth mod. For those that might not know, John has one of the largest Sega game collections in North America. It was a great honor to perform this mod for him and have him trust in me to do it. I've still got 3438 synth chips left...

Also some tunes from John's Genesis courtesy of Sonic 3 and Super Fantasy Zone for the Megadrive!

Sonic 3: Hydrocity Zone

https://www.dropbox.com/s/zth9b1nrh52yphi/3438%20Sonic3%20HydroZone%20Act%202.wav?dl=0

Super Fantasy Zone: Ya-Da-Ne

https://www.dropbox.com/s/udp5jper2ipco3p/3438%20Super%20Fantasy%20Zone%20Ya-Da-Ne.wav?dl=0

[goodtofufriday]

On 3/10/2017 at 7:03 PM, -^CrossBow^- said:

Just finished up John "The Immortal" Hancock's model 1 Genesis with the 3438 synth mod. For those that might not know, John has one of the largest Sega game collections in North America. It was a great honor to perform this mod for him and have him trust in me to do it. I've still got 3438 synth chips left...

 

Also some tunes from John's Genesis courtesy of Sonic 3 and Super Fantasy Zone for the Megadrive!

 

 

 

 

 

Sonic 3: Hydrocity Zone

 

 

https://www.dropbox.com/s/zth9b1nrh52yphi/3438%20Sonic3%20HydroZone%20Act%202.wav?dl=0

 

 

 

 

 

Super Fantasy Zone: Ya-Da-Ne

 

 

https://www.dropbox.com/s/udp5jper2ipco3p/3438%20Super%20Fantasy%20Zone%20Ya-Da-Ne.wav?dl=0

 

 

 

 

 

 

 

 

 

So Sorry to super Necro this post but it seems the original photo for the schematics are lost, imgur link is dead. Would you happen to still have it or a newer one?

 

Thanks

 

 

[+-^CrossBow^-]

6 minutes ago, goodtofufriday said:

 

 

 

So Sorry to super Necro this post but it seems the original photo for the schematics are lost, imgur link is dead. Would you happen to still have it or a newer one?

 

Thanks

 

 

Oh... yeah I hadn't have anyone request this in a LONG time. (Still sitting on a small stock of 3438s hehe). I might have copied the original scheme to my console docs folders so I will look in a bit. But, there is a slightly better way to do this now. FirebrandX  about a year or two after I did this, came out with a board to make this easier called the M1 Double Mega that allows you to have both the 2612 and 3438 on a single PCB with a switch to select which chip you want active. He hasn't made them in a while as he was trying to provide the 3438s to go with them and having issues with that. But might try and reach out to him to see if can get the boards made up so folks can try to source their own chips.

 

And yes... I did grab the pic of the scheme for this and have added it to this post.

 

 

[goodtofufriday]

47 minutes ago, -^CrossBow^- said:

-snip-

Thanks so much! And thanks for the lead on firebrands post. Does seem he's changed the circuit a bit with a 4 layer board.
 

 

[+-^CrossBow^-]

22 minutes ago, goodtofufriday said:

Thanks so much! And thanks for the lead on firebrands post. Does seem he's changed the circuit a bit with a 4 layer board.
 

 

Yes and I actually advise using his setup for this because you will notice the heatsink in that pic? That isn't for the 3438 as is a CMOS part I believe and doesn't get hot while it has been found that the 2612 gets really really hot and so having the 3438 piggy backed onto it, isn't likely that great a thing when you think about it. I actually removed the piggy back setup sometime ago when I used his earlier Double Mega boards and helped test them for him. His new design is much better as originally they were more L shaped and took up quite a bit space as a result. For instance, it didn't really fit until the RF shield anymore with the earlier setups.

 

But yeah I need to reach out to him and see if he has any of these ready as I've got 3438s on hand already to populate them with.