nfg.forums

So finally, the mod reached version 1.0 state.

It does all what previous versions did, but at much louder volume and long cables will not have negative effect on high freqs anymore :D
Output is about as loud as MCD RCA outs, and I'm more than sure its sufficient enough :)

Only drawback is added complexity, you have many more components now (about 50 or so).

Anyway, if anyone feels like doing one, and runs into issues, be sure to contact me :)

I've re-worked Tiido's fantastic little diagram into a proper schematic:



You can also download the schematic file for use with BSch3V Schematic creator (http://www.suigyodo.com/online/e/index.htm):

Schematic File (http://gamesx.com/grafx/TiidoMDAmp1.CE3)

you have couple of capacitors wrong, the ones on opamp inputs are 0.022µF not 22µF, and 3 capacitors are not marked as elecrolythics (2 on output lines, 1 on Vref signal) ;)

EDIT: and the 2 caps on power input are having their labels switched around, 100µF for elecrolythic and 0.1µF for the other cap.

Thanks for that.  Updated both the image and the source file with corrected values. 

Did I miss anything else?  =D

I can see some interection points that are missing like where the power input is, and I see ground touching the line that is supposed to be VCC, that can be quite confusing :P

Is the standard audio out from a G/MD 2 pre-amplified?

Quote from: Tiido Priimägi on June 25, 2009, 02:24:14 AM
I can see some interection points that are missing like where the power input is, and I see ground touching the line that is supposed to be VCC, that can be quite confusing :P

Image and schem file updated.

I fixed the two joins on power, but I don't see the ground touching VCC.  Can you clarify where that is? 

Quote from: Lawrence on June 25, 2009, 10:23:10 AM

Quote from: Tiido Priimägi on June 25, 2009, 02:24:14 AM
I can see some interection points that are missing like where the power input is, and I see ground touching the line that is supposed to be VCC, that can be quite confusing :P

Image and schem file updated.

I fixed the two joins on power, but I don't see the ground touching VCC.  Can you clarify where that is? 

Directly under the "All transistors are 2SC945" box.

Oops.  Fixed!

Quote from: antron on June 25, 2009, 08:07:51 AM
Is the standard audio out from a G/MD 2 pre-amplified?

it is preamplified in all MDs, and done poorly, particulary in MD2s, where sound is very filtered and distorted... this mod will make things unfiltered and undistorted, like Kega Fusion for example.

Tiido,

Op-amps are good for reducing the component count.

---

I would need a quad opamp for PSG and FM + a dual opamp for output part.... you will need some buffering on YM2612 outputs since they're rather high impedance and really quiet anyway, and if there's anything wrong you get massive distortion :/
Using additional opamp will result in more components really.....

Quote from: Tiido Priimägi on June 29, 2009, 09:04:32 PM
I would need a quad opamp for PSG and FM + a dual opamp for output part.... you will need some buffering on YM2612 outputs since they're rather high impedance and really quiet anyway, and if there's anything wrong you get massive distortion :/
Using additional opamp will result in more components really.....

Yeah, you'd need to get various signals at more or less the same impedance. Is there any DC bias on the PSG/FM signals? If there was you could get away with just a quad op-amp wired as voltage followers.

Also, what are you doing for a power supply to the op-amp? The '4558 isn't going to work very well with the Megadrive's single +5v rail.

FM is on 2.5V at least, but PSG is at 1V, and FM is like 20db more quiet than other signal sources.
The supply is single rail, and I know I'm underpowering the 4558,  but I have no other/better chips at hand, and these 4558 work perfectly.  I could use additional voltage regulator for say 7...8V supply, but that would make some biasing things more complex... using dual supply can make things nicer though, but I think the components you will use to get dual supply out of single supply will null the savings from other areas...


Anyway, here's a recording :

http://www.fileden.com/files/2008/4/21/1876835/MegaTurrican.ogg

don't tell me it does not sound good :P

Tiido,

Do you think it will work as well if I built it from parts in my own stock? Looking at a NE4558 datasheet, I doubt it.

There are lots of audio grade op-amps out there that will work just fine at 5v.

only 4558D is quaranteed to work, I do not care if other opamps will work withuot distortions etc.  I have no access to anything unless I put some money into it, and I'm short on it right now....

how it looks like in my MD2 :

Honestly ?


That looks like those chassis mounted old tube radios !!!!
Pretty neat, dude     ;)

And comparsions :D

MD2 CCAM 1.0 -> http://www.fileden.com/files/2008/4/21/1876835/TF4.ogg (http://www.fileden.com/files/2008/4/21/1876835/TF4.ogg)
MD2 stock -> http://www.fileden.com/files/2008/4/21/1876835/TF4_MD2.ogg (http://www.fileden.com/files/2008/4/21/1876835/TF4_MD2.ogg)
no TMSS MD1 (HiDef) -> http://www.fileden.com/files/2008/4/21/1876835/TF4_MD1.ogg (http://www.fileden.com/files/2008/4/21/1876835/TF4_MD1.ogg)

Still sounds amazing. Now if only emulators and VGM players would sound this crystal clear.

Oh... How it's hard to live without schemotechnic's knowledge... There actually no need to build such schematic. Just replace some capacitor's in op-amp section and it will have another frequency cut edge. Basic schematic cut out anything higher than 8-8.5 kHz. ^_^ If i find time i'll take some fotos of mine board with such audio mod.

the stock setup also distorts audio quite a lot even when its cutting most of the audible freq range.... lifting the filtering cutoff won't get rid of that, but it will make things cleaner sounding.

would you then say that this Model 2 Mod if done right gives the best sound from any version of Mega Drive/ Genesis modded or unmodded? If so this is helpful because the model 2 is the easiest to come buy and certainly cheaper than laseractive or wondermega.

Yep, it does give best sound than any unmodded version. All systems with 5487, 5600, 5608 and 5700 ASICs can have this mod (that includes Wondermega, Xeye, Nomad, CDX to name a few).

Forget just the Model 2; there's a particular model of the Genesis Model 1(VA7 motherboard only) that uses the same circuitry as a Genesis Model 2, complete with the same incredibly awful sound circuit.  I've built the prototype version of Tiido's circuit when I first found it on Sega-16, and while it is possible to get sound out of the Mono audio outputs via the RF modulator and Multi-A/V out, that old circuit was too weak to get a properly amplified sound output on the headphone jack.

That reminds me: Tiido, I have yet to pick up another VA7 Genesis Model 1.  They're still common as hell, but I haven't been looking around flea markets and the like around my area as much as I normally do, but I should be able to go looking for a VA7 Genesis Model 1 on Friday.  But even if I pick it up, there's a good chance I'll only be able to ship it in December.

In the meantime, I'll check to see if the new circuit, once I've built one, amplifies the sound enough to be heard well via the VA7 Model 1's headphone jack.

you will need an additional amp if you want as loud sound as you would get from a real MD1. The output should be around as loud as MCD RCA out.

I assume, then, that without the extra amplifier, I would still be able to hear something?  It won't be as faint as the prototype circuit(too quiet to hear anything)?

its little less loud than NDSlite.... too quiet for my taste but muuuuch more than the previous version.

Quote from: Tiido Priimägi on September 06, 2009, 06:47:15 AM
Yep, it does give best sound than any unmodded version. All systems with 5487, 5600, 5608 and 5700 ASICs can have this mod (that includes Wondermega, Xeye, Nomad, CDX to name a few).

Are there any CDXs out there with those ASICs?  Mine have 315-5660s... :(

There's really no point in adding Tiido's circuit to a Sega CDX, as its sound is already quite clear out of the box.  It's just a little quieter than most of the other Genesis systems.

Quote from: Ace on December 05, 2009, 03:57:17 PM
There's really no point in adding Tiido's circuit to a Sega CDX, as its sound is already quite clear out of the box.  It's just a little quieter than most of the other Genesis systems.

Really?  I dunno about that, it sounds pretty crappy to me.  There is a lot of distortion and nosie, partly due to the opamps it uses I'm sure but it definitely doesn't sound half as clear as the sample download songs from the mod.  Anyone else have a similar experience with their CDX?

I found the audio DAC though, it's a LC78835.  I can't make out what kind of opamp it is since the only marking is "4510" and my searches found nothing to match that.  Fortunately it is a standard dual opamp pinout so I was able to replace it just now with a better one (OPA2376).  Sound quality improved nicely but I'd still like Tiido's mod quality.  I'm thinking about running the opamp on a dual supply as well to improve the quality and maybe replace some of the caps (the audio actually runs through some electrolytic caps which I don't think are the best for audio).  

-Segasonicfan

I have a MultiMega around, and it does sound very nice, at least MD side... there is considerable amount of digital noise and video noise in the sound, particularly because of the compactness. You can fix this by adding a linear power regulator and use it to power all audio parts and nothing else. This is what I did in my MD2 and things became really nice when it comes to noises in sound.
I need to do more research around CDX / MultiMega, its compactness makes things quite challenging though. to get good sound, you will have to kick out the 315-5684, there's nothing you can do about it... I believe its some octal opamp by ROHM.

Quote from: Tiido Priimägi on December 07, 2009, 12:09:31 PM
I have a MultiMega around, and it does sound very nice, at least MD side... there is considerable amount of digital noise and video noise in the sound, particularly because of the compactness. You can fix this by adding a linear power regulator and use it to power all audio parts and nothing else. This is what I did in my MD2 and things became really nice when it comes to noises in sound.
I need to do more research around CDX / MultiMega, its compactness makes things quite challenging though. to get good sound, you will have to kick out the 315-5684, there's nothing you can do about it... I believe its some octal opamp by ROHM.

This is good information.  It's that digital and video noise that I can't stand despite the sound quality and so that's what I am trying to fix.  I already added a linear power supply to the video circuit separately but there was still a *lot* of video noise.  It wasn't until I used a linear 5v instead of the main supply that that really improved...and that was after I installed new caps for the old power supply.

I think your suggestion of using linear regulation for just the audio parts is a great idea...the only problem with that now is I will be cramming 4(!) 7805s in there which will produce some considerable extra heat.

I don't mind kicking out the 315-5684 as my soldering skills are very good.  Do you know the pinout for it?  If it is just an opamp I would to replace it but I can't tell what it is at all.  I did trace the audio lines to the lower CD PCB and to that DAC and subsequent opamp I mentioned.  if you think it would help I would be glad to post pictures on my findings.

Let's make the CDX/multimega the best tiny Genesis/MD is out there! :)

-Segasonicfan

its better for you to use the existing switcher for video and all else and single 7805 for just audio... it will be nice challenge to sseparate all audio related parts' power supplies :P

I gave my MD2 a LM2676 for digital and video stuff and used the existing 7085 for all sound things. I can give you pins of the sound power lines on the Sega ASIC. Main reason I use another 5V supply in my MD2 is that I was overloading the poor 7805 quite a bit with the mods I have added... This is what I've done to my MD2 :
http://www.fileden.com/files/2008/4/21/1876835/MD2front.jpg (http://www.fileden.com/files/2008/4/21/1876835/MD2front.jpg) :P

http://www.fileden.com/files/2008/4/21/1876835/MixerChipSchematic.jpg (http://www.fileden.com/files/2008/4/21/1876835/MixerChipSchematic.jpg)
Here's a schematic of the mixer chip in MD2 VA3, it seems to be same in MD2 VA4 also. Nomad has thigns a bit different, I've yet to work out a schematic. 32X uses same chip too and things aren't really different, except there's unused input pins (which should be tied somewhere to reduce noise...).

Any info and images are helpful. Schematics tell more than 1000 words :P

Thanks for that schematic Tiido!

The reason I used a separate 7805 instead of the switcher was because of the massive video noise my CDX had.  Apparently they revised the DC-DC in some later CDX's/MultiMegas to make this a little bit better.  but I couldn't stand the video, there were diagonal noise lines rolling up and down the screen periodically and especially on certain colors.  It wasn't until I cut the main +5v and used 2 7805s  (to get enough current) instead that this went away:

http://i18.photobucket.com/albums/b134/Segasonicfan/cdxaudiomod4.jpg (http://i18.photobucket.com/albums/b134/Segasonicfan/cdxaudiomod4.jpg)
(picture of where I cut and added the new power supply)
http://i18.photobucket.com/albums/b134/Segasonicfan/audiomod2.jpg (http://i18.photobucket.com/albums/b134/Segasonicfan/audiomod2.jpg)
(pic of the new 7805s- that copper is very convenient :))

It shouldn't be too hard to separate the audio parts' power supplies as long as I know what all of them are.  Your schem should be enough because I found the parts on the sub board:
http://i18.photobucket.com/albums/b134/Segasonicfan/CDXaudiomod.jpg (http://i18.photobucket.com/albums/b134/Segasonicfan/CDXaudiomod.jpg)

That's the opamp I replaced and the DAC.  The hand soldered sub board that is a fix Sega installed with every CDX unit I've seen is also something working with the audio and should have its +5v from the 7805 as well (I believe they made it easy by using red wire even).

So the parts to separate power are:
LC78835
'4510' opamp (or replaced better opamp)
315-5684

The LM2676 looks great for a 7805 replacement.  Won't generate as much heat either.  Though fitting inside a CDX might be hard and ideally it would be nice to find a newer chip out there designed specifically for low noise apps with high PSRR and all that.  I'll look around.

It looks like that schem has all the info needed to replace the 315-5684 with the better mixer circuits from this thread, correct?
Glad this project is finally going through, looking forward to hearing your findings.

-Segasonicfan

There should be 2x DACs there, LC7883 that is for CDDA(at least in MegaCD2, seems CDX uses something else) and LC78835 that is for PCM chip.

Regarding LM2676, it did gave me some rolling lines in video, but that got fixed by adding a 100µF cap on the video encoder power pins. I would replace all of the original switcher circuit with some of the modern switchers, they're certainly much more efficient (the LM2676 does not even get warm in my MD2, its the 7805 the heatsink is for, hehehehehehe). I plan on giving my nomad a LM2676, it sohlud give a lovely extra hour of battery life (I want 10 hours, and i'm not too far from getting it).

You can just put my circuit on top of the 315-5684, the volume levels of all signals are right so no adjustments need to be made, just desolder the chip, get rid of some extra components and those series and parallel capacitors everywhere on the audio lines and you're done. You might replace the 4558D with something else, but it needs to have at least 3MHz of bandwidth (I'm not doing too much filtering, and YM output can carry freqs up to few hundred KHz !!!)
I just remembered that there is headphone output on the CDX though, I will look into it first... but I have school coming tomorrow so I cannot do any work on this subject until Saturday.

Egh...having trouble finding the other DACs..
I got the rolling lines on video from the default setup but I'll try that extra bypassing.

Tracing the 31-55684 is proving extremely difficult...I can't even find the placement of the components to remove (since it is a 4-ply PCB after all...) are you having any better luck with this?
What is the 4558d?  Is that the opamp that I could not identify?  That was located by the headphone out which is what I've been working with (or rather, the line out which looks to be wired up pretty much the same minus the pot).

I'd love a picture of your ultra modded MD2 with a description of what you've done.  It's looks like you've tried a lot of new things and it is very interesting.

-Segasonicfan

4558D is the opamp I use in my sound mod :P

I have not messed with the setup yet, i've got some other commission things to work out first.

Regarding my MD2, I'll make a shot with comments sometime in nearer future. There's quite a lot of stuff done, some of which is never done before, at least not that way.

looking forward to your MD2 desc. and working on this project more when you get the time.  Until then I'm going to experiment with what we've been talking about i.e. bypassing what audio circuits I can find and putting in better power regulation.  In the future I would love to tackle the 315-5684 mod with your help.
best,
-Segasonicfan

MD2 shot with comments - http://www.fileden.com/files/2008/4/21/1876835/MyMD2frontShotComments.jpg (http://www.fileden.com/files/2008/4/21/1876835/MyMD2frontShotComments.jpg)

And I got a small accident yesterday so I'm a bit immobilized... http://www.fileden.com/files/2008/4/21/1876835/Immobilized.jpg (http://www.fileden.com/files/2008/4/21/1876835/Immobilized.jpg)

thanks for the pic, looks very nice!  I didn't even know the MD couldn't do FM in Mark III games heh. 

It would be nice to tackle this 315-5684, have you actually replaced it before or just wrote up the schem?  Finding the input caps in a CDX is such a pain..

-Segasonicfan

Somebody sent me an e-mail though this forum, but I don't think I could have just replied it so I posted the required info here. This applies for VA0 and VA1 MD2s (there's very minor differences between those 2, but in essence all is same). I have VA3 setup too, but i have not yet uploaded it, I'll upload it if its being asked for :)

How difficult is this mod to perform? I've been thinking of trying it myself along with a few other idea's I've had but I'm terrified that I'd somehow kill my Genesis in the Process.

Quote from: Tiido Priimägi on June 23, 2009, 07:38:27 AM


So finally, the mod reached version 1.0 state.

It does all what previous versions did, but at much louder volume and long cables will not have negative effect on high freqs anymore :D
Output is about as loud as MCD RCA outs, and I'm more than sure its sufficient enough :)

Only drawback is added complexity, you have many more components now (about 50 or so).

Anyway, if anyone feels like doing one, and runs into issues, be sure to contact me :)

I guess I have 2 questions. 1, why is this not done on mega drive 1 (why did you choose #2?) and then...why? lol

The Megadrive 1 has stereo output..sounds pretty good to me. :)

Read the previous posts in the thread, please. The first model Megadrive/Genesis is widely recognized to have superior sound hardware to most of the subsequent revisions, but for whatever reason the model 2 console is more common.

Asking why someone implements a game machine mod is like asking why someone climbs a mountain. Most of the time, we do it strictly for the sense of achievement. Certainly, the well-tested and well-researched OEM hardware is good enough for most applications, but at GamesX we're hardly representative of the gaming public at large. We like SPDIF, we like channel-separated waveforms, and we like standardized connectors. When asked why, I counter 'why not?'

I did it on MD2 because MD2s have extremely poor sound, but comes out that after the mod, the MD2 that osunds the worst has the best sound from all the MD hardware there is.... ironic, hehe.
I only had MD2 when oding the mod, and I did it just to hear GOOD sound as I was very unhappy with the MD2 sound, I had a MD1 before which died and which sounded muuuuch better.

I've become a bit of an audiophile, MD1 has horrid output, very muffled and not exactly clean... I will look into making a mod for MD1 sometime....

thought Tiido might find this interesting, this guy claims to have an early Mega Drive 2 that had very few models released and is kind of like a Model 1.5 as far as the internals go, or so he claims, I don't know enough about the hardware to varify this, but I thought I would show you guys.

http://retrocopy.com/forumthread/239-2/glitches-and-emulation-errors-in-mega-drive-retrocopy-0720.aspx#post_1520 (http://retrocopy.com/forumthread/239-2/glitches-and-emulation-errors-in-mega-drive-retrocopy-0720.aspx#post_1520)

Quote from: panzeroceania on March 23, 2010, 07:10:50 AM
thought Tiido might find this interesting, this guy claims to have an early Mega Drive 2 that had very few models released and is kind of like a Model 1.5 as far as the internals go, or so he claims, I don't know enough about the hardware to varify this, but I thought I would show you guys.

http://retrocopy.com/forumthread/239-2/glitches-and-emulation-errors-in-mega-drive-retrocopy-0720.aspx#post_1520 (http://retrocopy.com/forumthread/239-2/glitches-and-emulation-errors-in-mega-drive-retrocopy-0720.aspx#post_1520)

That looks identical to my VA0 Model 2 Genesis.

it is a JP VA0 MD2, and I cannot imagine it sounding anything one would classify as "good"...

I suppose I am a dumb dumb when it comes to electronics but isn't that huge cluster ball of resistors/capacitors/amps a good antenna for interference? Is this mod effectively one that seeks to drastically improve the signal-to-noise ratio of the MD while cleanly amplifying it?

Sorry for ultr@ late reply,

Yes, that cluster can pick up interference, but so far I've not got anything, especially with shielded cables in use. Most of the interference is in MHz range, and filtered out anyway, so it should not be an issue at all.
Only really sad thing is that FM signals carry great deal of noise from VDP when exiting from the chip.... damn Sega :(

Is this mod appropriate for use with the Sega CD? Like will the audio for Genesis still be on the same volume level as Sega CD?

The sound levels are all good, but only problem is that MegaCD RCA outputs will not carry MD sound, but MD side will have all sound at correct levels, and clearer than what MEgaCD RCA's give (there's a small design choice that will muffle the sound a bit on the RCAs).

Is it possible to use transistors BC847B(BC850B) instead of 2SC945?

This mod is the best thing that has ever happened to my MD2  :)

I used an OPA2134 instead of the 4558D. It sounds fantastic. At first the low tones was a little fuzzy, but now, after plenty of "break-in", it sounds like angels licking you in the ear.

If I had more money than brains I'd rebuild it with 2x LM394 and 2x OPA627 and feed it with some sort of yummy dual rail supply.
Probably wouldn't be able to hear the difference  ;D

Quote from: Tiido Priimägi on December 08, 2009, 08:24:43 PM
I gave my MD2 a LM2676 for digital and video stuff and used the existing 7085 for all sound things.

This got me curious. So I gave my CCAM a 7805 of it's own, just to see what happended:



It killed the video hum completely! No more annoying buzzing sound when there's alot of white on the screen  :)

I can't recommend this addition to the mod highly enough!

Tiido, the Thunderforce IV tracks sound terrific, great work!  ;D

I've tried to apply the CCAM to my PAL VA0 Mega Drive 2. Unfortunately I don't get a sound out of the MD2 at all except for the "ZAP" sound when switching on the console.
On Sega-16's CCAM Thread I've found this diagram (http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=511814&viewfull=1#post511814) which I based the mod on.
(http://i.imgur.com/1e7d5.jpg) (http://i.imgur.com/bliRC.jpg)

On the MD2 mainboard I used following points to get power and the signals:
(http://i.imgur.com/Nxu2U.jpg)

Does anyone realize what I might have done wrong? Is it important to connect to MCD- & 32X-L+R when testing the mod?

The pinouts on your board does not match the 2SC945. Are you using a different kind of transistor?

Quote from: micro on December 16, 2012, 06:27:26 AM
On Sega-16's CCAM Thread I've found this diagram (http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=511814&viewfull=1#post511814) which I based the mod on.

The links/pics in the tread are dead  :-\

Quote from: KillingBeans on December 17, 2012, 10:58:18 PM
The links/pics in the tread are dead  :-\

Here you go:
(http://i.imgur.com/OFkZJ.png) (http://i.imgur.com/W7zfD.png) (http://i.imgur.com/1e7d5.jpg)
Mirrored for comparing to the bottom side:
(http://i.imgur.com/YGjpt.png) (http://i.imgur.com/bliRC.jpg)

Quote from: KillingBeans on December 17, 2012, 10:58:18 PM
The pinouts on your board does not match the 2SC945. Are you using a different kind of transistor?

No, not at all. I used this transistor  (http://www.reichelt.de/2SC-Transistoren/SC-945/3//index.html?ACTION=3&GROUPID=2900&ARTICLE=26827&SHOW=1&START=0&OFFSET=500&&SID=13UMeaWn8AAAIAAAJmMbYc932cdfb8a1fa33995391d8a1d857ee6&LANGUAGE=EN)(datasheet here (http://www.reichelt.de/index.html?;ACTION=7;LA=3;OPEN=0;INDEX=0;FILENAME=A100%252F2SC945_CDIL.pdf;SID=13UMeaWn8AAAIAAAJmMbYc932cdfb8a1fa33995391d8a1d857ee6)) and that op amp (http://www.reichelt.de/ICs-NE-STV-/NE-4558-DIP/3/index.html?;ACTION=3;LA=446;ARTICLE=13351;GROUPID=2915;artnr=NE+4558+DIP;SID=13UMeaWn8AAAIAAAJmMbYc932cdfb8a1fa33995391d8a1d857ee6) (datasheet (http://www.reichelt.de/index.html?;ACTION=7;LA=3;OPEN=0;INDEX=0;FILENAME=A200%252FNE4558%2523PHI.pdf;SID=13UMeaWn8AAAIAAAJmMbYc932cdfb8a1fa33995391d8a1d857ee6)).

I thought the pinouts are ok. +5V to the collectors of all four transistors. PSG and FM(+22k) connected to the bases; emitter goes to the right side to the op amp... ???

My mistake. Didn't look propper at your board.

(Note to myself: Don't try to be a smartass when you haven't slept in three days)

I guess there's only one way of finding the error. A continuity tester and a lot of patience.

BTW, I've made this schematic. IMO it shows the signal paths and the function of the circuit a little more clearly:

IT WORKS!  And it sounds awesome! ;D

Thanks alot, that really helped. It turned out there was a problem with the 470 Ohm resistor that should be between GND and the center point of the two negative input pins. On my board both ends of the 470 Ohm resistor were tied to GND which rendered the resistor pretty useless of course.

The diagramm is kinda misleading concerning that resistor. The resistor is drawn small and is located between two holes. So I thought the resistor's leads should go through these two holes...
(http://i.imgur.com/4VP1q.png) (http://i.imgur.com/jty80.png)

Glad i could help  :)

Does any one sell complete component kit or complete board?  :D

TmEE might have some:

http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=536804&viewfull=1#post536804 (http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=536804&viewfull=1#post536804)

And there's this guy making SMD versions:

http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=547716&viewfull=1#post547716 (http://www.sega-16.com/forum/showthread.php?7686-Crystal-Clear-Audio-Mod-for-Sega-Mega-Drive-2-amp-Genesis-2-version-1-0&p=547716&viewfull=1#post547716)

I'm also gonna make a batch of PCBs myself at some point.

Thank you so much  ;)

EDIT: Havent read all messages but Tiido Priimägi how the f*ck did you figure this out?

Im excited to see all the work still happening on this! :)  The new SMD boards are out, and they are sexy (see the Sega-16 thread linked above).  Im determined to get my CDX modded with this.  After fixing the video in that system for clean output I feel like this is the last thing needed to make it the perfect mini sega console  :D

-Segasonicfan

Quote from: Tiido Priimägi on December 09, 2009, 02:00:58 PM
There should be 2x DACs there, LC7883 that is for CDDA(at least in MegaCD2, seems CDX uses something else) and LC78835 that is for PCM chip.

You can just put my circuit on top of the 315-5684, the volume levels of all signals are right so no adjustments need to be made, just desolder the chip, get rid of some extra components and those series and parallel capacitors everywhere on the audio lines and you're done.

At long last, I've traced everything inside the CDX to do this mod.  See the pics here:
http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM3.jpg (http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM3.jpg)
http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM2.jpg (http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM2.jpg)
http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM1.jpg (http://s18.photobucket.com/albums/b134/Segasonicfan/?action=view&current=CDXCCAM1.jpg)

It looks as though the 315-5684 doesnt mix the MCD L and MCD R (Sega CD audio).  The LC78835 outputs to an opamp on the subboard which mixes the audio into the 315-5684s audio outputs.  I havent desoldered the chip yet to double check, but the pins do not appear to be connected from what I can tell.  So my question is, can I just remove MCD L and MCD R from the circuit?  I think it should work fine that way.

FYI, I upgraded my opamp so yours will look different.  And Ive attached Tiidos very useful schematic which made all this tracing out possible.

-Segasonicfan

---

Alas, its been done!  I bought Retrogamer343s neat little SMD board of Tiidos audio mod and installed it in my CDX.  Works like a charm and sounds superb :)

I desoldered the 315-5684 and provided a pic below to show the traces underneath.  I was right about the MCD audio lines not being mixed in there.  Oddly though, pins 4 and 5 are not used as well, which has me scratching my head since those are supposed to be audio out pins. 

The last thing I have left is to mix the audio into the audio out jacks on the CD motherboard.  I thought it would do this after I connected it to the audio out on the AV port but I was wrong.  Really not sure how it does this natively since the only output pins on the 315-5684 for audio are run through some caps and resistors and into the...315-5619(?!) which is supposed to be a Z80.  Very strange.  Also, the pins connected the two boards have audio lines ties to the AV port, but somehow this isn't giving me audio on those jacks. 
Ah, worst case I can just solder to the jacks themselves!

-Segasonicfan

---

315-5684 Schematic now online!  Thanks to omp at Sega-16 forums there are schematics galore for Mega Drive, Mega CD, 32x, etc :D

http://www.sega-16.com/forum/showthread.php?23228-Sega-Service-manuals-16bit (http://www.sega-16.com/forum/showthread.php?23228-Sega-Service-manuals-16bit)

---

Dont know if anyone is still reading this thread and following what I'm posting, but I'm excited about getting a CCAM into the CDX and hopefully someone out there is willing to help

Genesis mixing is done and works perfect.  Mixing into the CD has been a lot trickier though, since it is not clearly seperated like MD/Sega CD combos.  Apparently (after a looot of tracing and such) I've found the 315-5619 is a DAC for the PCM chip (315-5476A which is a RF5C164A).  It looks like this is the equivalent of the LC78815 in Mega CD2.  Figuring out the outputs to that is going to be a real pain, as will be mixing them properly.  I have a mix that works right now, although the quality is a little lower since the CCAM output is having to be fed into this mixing stage.  I am pretty sure Sega went this route to integrate a lot of the opamps used on the output stage of the DAC.  If anyone has any ideas on what this might be a "mock' rebranded chip of that would help though.

-Segasonicfan

---

It's been a while since I wanted to do this.
I made a layout using Eagle 6.1.0. I'm including pdf files for printing layout and infos for those who don't have the above.
CCAM Project (http://www.mediafire.com/download.php?x2wlcax3xbkqobk)
Best  ;D

Seems like the best mod is to just buy a VA3 or 4 console.  My CXA1645M equipped stock VA3 sounds better than a CCAM modded VA2!

Finally figured out everything to adding a CCAM mod to the Sega CDX (for those crazy enough to try).  Details all here:
http://www.sega-16.com/forum/showthread.php?29425-Live-presentation-on-Sega-CDX-Hacking-%28Youtube%29&p=706463&posted=1#post706463

Thanks for your help Tiido!

Thanks for the update, segasonicfan!

But that page has an attached JPG which can't be viewed by anyone without an account there.  =(

Quote from: Lawrence on February 22, 2015, 07:34:25 PM
Thanks for the update, segasonicfan!

But that page has an attached JPG which can't be viewed by anyone without an account there.  =(

Good point!  Here ya go:
http://s18.photobucket.com/user/Segasonicfan/media/Sega%20CDX/CCAMforSegaCDMixing_zps14fdea06.jpg.html
http://s18.photobucket.com/user/Segasonicfan/media/Sega%20CDX/CDXCCAM1_zps1a63fc52.jpg.html
http://s18.photobucket.com/user/Segasonicfan/media/Sega%20CDX/CDXCCAM2_zpsd628807b.jpg.html

this one is just explaining stuff: http://s18.photobucket.com/user/Segasonicfan/media/CDXCCAM3_zps6d952a10.jpg.html

Too bad attachments on this site are limited to 512kb :(  otherwise Id upload em here

Aha!  Well, I fixed that - the new limit is much larger.  Will 2MB be enough?  =)