Idea for a new Genesis\MD mod, need some help.

Ok. So I've been thinking about the Expansion Port that is used for the Sega CD.
As you may or may not know the Genesis Model 2 has the ability to run the audio through the expansion port back to the Sega CD for mixing, that way you can connect it to the TV using the twin RCA jacks at the back of the Sega CD. The Model 1 can't do that as it is wired differently. What you need to do with the Model 1 in order to get audio out through the Sega CD is to bridge the headphone jack to the back of the Sega CD using the "MIX" PL connection.

What I want to do is to wire the audio that goes to the headphone jack directly to the expansion port pins that would have supplied the Audio Out if it was a Model 2. That way I can get stereo sound when using the Sega CD without connecting anything to the front of the console.

The problem:
I don't know that pinout of the expansion port of the Model 2 Genesis. There is one here for the Model 1: http://www.gamesx.com/cartouts/gennyport.htm
But I can't tell where audio in and audio out is for each stereo channel. Has anyone done this before?

 

Why not just mod the Genesis with stereo audio jacks in the back? That would be a little easier than what you propose.

 

That might be a better idea, running the audio out that normally comes out the front headphone jack to a new one on the back. The reason this might be better is you can still use the volume slider to control the volume balance to your preference between the Genesis and Sega CD audio. And then a much shorter patch cable could connect that to the Sega CD.

With no modding though you might be able to find or make a nicer cable for the task. Something with a right angle at the jack in front with a length to go around the back neatly but without alot of extra cable making a mess.

 

I do with mine what Apolloboy recommend I just run the stereo to the back of the genesis and put some jacks problem solve.

 

Great idea. I don't think anyone has ever done it. I really like the idea of not having to deal with all that extra wiring.
Have you tested and confirmed that plugging a Genesis2 into a CD1 lets you do this? I don't have a CD1 so I never tried it.

Anyway, the connections you're looking for are:
A27 SR3
B27 SL3

From the 5-1 schematic in the service manual if you want to verify
Good luck. I'm doing a BIOS mod on one of my MCD2s this weekend and will probably have a look at this to this as well.

 

Modded one of my MD1 with this. Just wired the L/R pins that go to the headphone board to A27/B27. Now I get CD and console sound out of the CD audio out on my MCD2. Console sound volume can be controlled with the volume slider.

It's a simple mod that took about 15 minutes but it will be really nice to not have to tentacle rape the headphone jack to use the CD any more.
I don't have a MCD1 to test it on but worst case scenario you'd have to also mod the MCD1 to take the audio from the console interface to the mix jack.
I took a few pics if you want to see how it was done but it's literally just soldering those two wires. If you need any help with it just let me know and thanks again for this simple and useful mod.