Gen 3 Stereo (VA2) Success!

[Segasonicfan]

I bought a Gen3 recently for modding (S-video and whatnot), but was suprised when I cracked it open to find a different chipset.  My unlucky self got stuck with a VA2, but I decided to go ahead and mod it anyway thinking the only thing I was compromising was the overclocking mod (68000 is integrated).

Then I found out the sucker ONLY outputs mono.

This wasn't like Sega's usual work though of just leaving an unfinished section in case it was needed.  They left no trace of a R speaker input in the board. So I went directly to the source...

I traced around the processor for the audio lines.  What I discovered was strange though: audio L, audio R, and SFX(?).  Appearently the 3 are mixed and then sent off to the LM324 for amping.  Appearently Audio L and SFX are to be combined as Stereo sound effects (like Sonics ring chimes) are not really part of the SFX output but are integrated into R and L.  

To get stereo sound you must break the link between the processor outputs and then seperately amplify R using an opamp.  You can use another LM324 (which Sega did in the Gen 2) or similar chip.  Here's a pic describing the instructions along with the import jumpers I found:

[Altima1994]

Wow, excellent job man! Thanks for sharing it with us here. I can't wait to see your final mod picture.

[Segasonicfan]

Here's the final mod pics (just finished):






The inside's a little messy in this pic but I cleaned it up a lot more.  I just pulled the opamp from a broken Genesis 2.  The audio feeds into 3 opamps within the LM324 to amp up to full line level output.  I also added a D-Sub RGB out so I can connect my component converter

-Segasonicfan

[FM-77]

Looks neat! Impressive work!

However... what did you do to your Sonic 3 cart? Dropped the soldering iron on it?    

[Guest_rgb32e]

Where did you get your rgb to component convertor?

[Segasonicfan]

Where did you get your rgb to component convertor?

I built it myself...see my website for info.

I should also mention that the Gen3 outputs a screwy sync...I had to use a sync splitter to get it to work on my RGB monitor.  

-Segasonicfan

[Andy Katzenmoyer]

Where can I find a simple OPAMP diagram to amplify the R audio signal? Anyone care to help me?

-Andy

[Guest]

Sega uses the LM324 and I think it's a fine choice.  You can download the datasheet from National's website.

-Segasonicfan

[Happy Buddha]

Finally had time to do the mod myself. Thanks Segasonicfan for the info. However I noticed the audio from  the lelft channel was pretty distorted. The right channel is fine. Any idea what I might be doing wrong? Thanks.

[ken_cinder]

Do you sell the RGB > Component converters you make?
If so, what do they cost, and can you mount phono jacks for the input lines? (I like clean plugs, as I tend to move things around and I'm working on a portable arcade unit atm)

[Segasonicfan]

Happy- the LEFT was distorted??  That doesn't quite make sense because that channel uses the opamp circuitry already inside the Genny 3.  Sorry i don't know what you are doing wrong there :/

Cinder, I don't sell those converters yet but I am in the process of having PCBs manufactured to sell.  

-Segasonicfan

[ken_cinder]

Alright, when you do, be sure to drop me a PM. If you can better the price or better the features at the same price as JROK, I'd definitely want one.

I want my portable to be able to hook up to a TV as well.

I'll show you guys what I'm working on when it's more together. Suffice it to say, portable JAMMA with the ability to use pretty much anything else inside the setup as well, like my Xbox.
The ability to go Component > RGB would kick ass as well, the cost of buying component cables to hack up would be enormous as finding another Gamecube Component cable is a very expensive proposition, and right now in my portable setup I'm limited to Composite from anything but JAMMA.

[Happy Buddha]

Hi SegaSonicFan,
Here's the picture of my genny. I think I pretty much follow your instruction.
Spot something that I missed? The brown PCB is another LM324 for the right channel. Thanks.

[Segasonicfan]

Happy- I'd love to help but it is *really* hard to see your work without a higher res pic of the main PCB.  You also used green wiring so I can't distinguish much against the green PCB.

From what I can tell however, it looks like you have a green wire running from the onboard opamp or something...what does this go to?  It also looks like maybe you didn't break the audio resistor connection well enough.  Anyway if you can take a better picture I can help you a lot more.  Use photobucket or a similar site as they offer up to 1MB free pic uploads.  You can also email me at segasonicfan@gmail.com if you like.

Cinder- I am making the board with someone in order to have something priced cheaper than the JROK.  I'll let you know when it's done.

-Segasonicfan

[Happy Buddha]

I have a working stereo mod now. Thank you SegaSonicFan for your help. As for the LEFT, I soldered the wire straight from the output jack hahaha should read the instruction carefully next time.

[Segasonicfan]

Glad to hear you got it all working

-Segasonicfan