MegaCd and stereo sound question

[CurlyPaul]

I have an MD1 and an MCD1 and I would like to know if its possible to route the stereo sound from the headphones thru the expansion port like the MD2 does?

Thanks

[MEGADRIVE Jeroi]

I have an MD1 and an MCD1 and I would like to know if its possible to route the stereo sound from the headphones thru the expansion port like the MD2 does?

Thanks

In theary yes, as the sega MD2 uses same extension port than MD1. Tho you will need to add some wires inside MD1 and also MCD1 Also keep in mind while you do this, that dont break the pcb lines what so ever to maintain normal cableing support as this will be hack mod and then making md1 supporting only single way of working.

Regarding to the mod:
You will need to find in what pin MD2 uses to carry stereo to to MCD2. Then search the same pin and connect aaudios to there.

[CurlyPaul]

Cool thats pretty much what I thought. I'll get some wire, find some diagrams of the port and let you know how I get on.

[CurlyPaul]

Cant seem to find any, does anybody have a link to a pin diagram of the edge connector that plugs into the MCD?

[Chilly Willy]

http://emudocs.org/Genesis/mega1.png

That page has lots of good MD info.

[CurlyPaul]

Thanks for the link, loads of techy diagrams there, thanks!!

[MEGADRIVE Jeroi]

Thanks for the link, loads of techy diagrams there, thanks!!

http://www.gamesx.com/cartouts/gennyport.htm

Looks like you wire a29 for left and b29 right...

[CurlyPaul]

fantastic, thats just what I was after. Thanks very much

[MEGADRIVE Jeroi]

I checked all voltages when Megadrive game is connected and turned on and checked the extension port pinout voltages for all three regions. All regions had same voltages so no differences here. Only difference with MD2 is probably that audio pins are used by it. As you see from my voltage tests, there is no voltage aplied to audio pins on megadrive1:



Here I wonder if the cartpin is used to check cart region code. If this is true, then it must carry +5 or GND depanding on game. I will try pal game also so I can check if the cart pinprovides GND when game cardrisge is connected.

I tested now the md2. There was no difference inaudio pins how ever, the not used pins are used in md2 voltage is : 2,5v so I am assuming that md2 uses NC pins on next to audio pins for audio, some one who knw better can tell more. It seems that allnot used pins on MD1 is used by MD2. Maybe TMEE knows where the audio goes in expansion port for mega cd.

Resolution:

MD2 uses 2 pins A27B to output audio. AS told the B27B pins next to audio is where to connect headphone pins but it may provide oscillationproblem as I did discuss with TMEE.

1. Try to solder straight cable to A27B where right is A and Left is B.
2. If not working sound when CD connected here is what you need to do with dual op-amp:

[Jorge Nuno]

No, the region isn't detected using pins, it's part of a register and its checked by the CPU if the game tells to do it.

The MD2 uses pins A27 and B27 for carrying the audio back to the MCD/SCD «- These are NC for MD1 systems.
Those A29 and B29 are for routing the CD expansion audio to the MD amp (the opposite way)