Crystal Clear Audio Mod for Sega Mega Drive 2 & Genesis 2, version 1.0

[KillerBean2]

Ahh yes, I forgot about that. So i works just like in the MD1 where one half of the LM358 takes care of the mono sound amplification and the other half deals with the software reset?

[TmEE]

Yep, exactly

[KillerBean2]

I'm gonna start building a new amp and put it in one of my other MD2s. And this time I'll leave the old op amps alone!

Small question regarding the 75 Ohm resistors on the MCD lines going to GND:
Aren't those redundant when you tap the lines from CE8 and CE10, since the two original 75 Ohm resistors on the motherboard are still present?

[TmEE]

You don't need 75ohm ones when you leave the ones on mobo alone. If you got doubles then MCD will be quiet

[KillerBean2]

I tried a different approach today.

I transplanted my birds nest CCAM to another MD2. Then I restored the PSG and FM lines and placed 2x OPA4134 where the old op-amps used to be. I also put in new 10uF capacitors.

Now the MD2 sounds just like a normal MD2, but without any noise at all. I can't really decide whether I like the sound of this or the CCAM better.

[KillerBean2]

Nahh, I f¤¤ked up (again). Now one of the FM-channels keeps crapping out on me, and I can't figure out why

[MEGADRIVE Jeroi]

I tried a different approach today.

I transplanted my birds nest CCAM to another MD2. Then I restored the PSG and FM lines and placed 2x OPA4134 where the old op-amps used to be. I also put in new 10uF capacitors.

Now the MD2 sounds just like a normal MD2, but without any noise at all. I can't really decide whether I like the sound of this or the CCAM better.

Can you post ogg of it? Also, with noise, do you mean that you got rid of vdp noise of megadrive? If that is true, then you are a hero! Appllying the op-amps and ccam togehter would clear the system sound even more than just ccam as ccam has the vdp noise which I dont like even tho the game do sound very nice.

[KillerBean2]

Can you post ogg of it?

Not at the moment. I'm still loosing the right audio channel on the MD2. I think I might have been too forceful when plugging in my RGB-cable at some point, and have messed up the AV-jack

Appllying the op-amps and ccam togehter would clear the system sound even more than just ccam

The CCAM bypasses the old op-amps. It wouldn't do anything for the sound, if you replaced something, that aren't being used.

ccam has the vdp noise

I don't get any VDP noise with the CCAM. What dual op-amp are you using for the CCAM? I'm using the OPA2134, and it kills all noise like a champ.

I'm also warming up a bit to the CCAM. At first the sound was to high pitched and transparent for my taste. But now as the circuit is getting closer to the "break-in", the bass is much better defined, and it begins to sound a lot more like a true MegaDrive. It's awesome!

Btw, PM me if you really want a broken Nomad

[Drakon]

I built and installed this circuit yesterday/today. It's way better than I expected. I like it even more than a pre-va7 model 1. I think it's better sounding than any audio circuit built into any model of the genesis. Here's pics and a video

http://www.sega-16.com/forum/showthr...-region-switch

[Drakon]

Here's a video showing the difference in audio quality before and after I installed the CCAM

[MEGADRIVE Jeroi]

Here's a video showing the difference in audio quality before and after I installed the CCAM

Tmee, this could be added to the first post.

[MEGADRIVE Jeroi]

Here is layout image and printable board layout to produce board by etching. Image and pdf attached. Courtesy of me ofcourse. Used 8 hours total to create schema and work with layout and needed board size to fit audio slot of md2.

Edit: I uploaded improved photo and layout. Because I did see a way to get the board width 1cm smaller . Also same kind of componenets are now identical positions on both sides.

And I used 1/4 resitor values. I am tempted to rewrite this layout with 1/8 size resistors. Should make even smaller board again.

[aodinets]

I am working on a CCAM 2.0 that won't require transistors but few nice opamps instead and much less resistors, but it will probably need dual polarity power supply for maximum efficiency

TmEE, Is there any progress on CCAM 2.0? I'm very interested in it.

[MEGADRIVE Jeroi]

TmEE: Where does the Sega mobo take the V- for OP amps? You could take minus voltage from those pins so that your OP-AMP circuit without making negative voltage on your own. To make minus voltage easy, first use voltage converter chip, then your OP-AMP's in series. This way you can take V+ and V- from Sega +5v. However, if you find the V- from Sega mobo it's easy to take minus volt from there. Even One OP-amp can work as minus voltage source, You make inverting op-amp circuit from first op-amp then wire couble dual op amps for making the sound.

On side note, I have nearly completed the 1/8 version layout of V1 and will post it soon here also. The mobo has made huge space saving with 1/8 size resistors.

[aodinets]

TmEE: Where does the Sega mobo take the V- for OP amps?

Maybe, something like MAX768?