Hmm, I seem to be posting a lot for a confirmed lurker... I promise I'll stop soon.
I mentioned on the other thread I started that I was looking in to doing an AY sound chip upgrade for the ADAM.
Well, there's some marvellous SGM games to be played but I don't have a SGM. Also, as I understand it, the ADAM will run a good deal of the SGM catalogue... quietly! (I added an extra 64k to mine a while ago)
As my main interest in old computers is tinkering with them I thought I'd take a crack at a SGM-compatible sound board to stick in my ADAM. I guess it would work in a Colecovision too, but without the extra RAM I don't know how useful it would be...
-Come up with an AY-based design that won't be too hard to make
-Do it on the cheap, so try to stay away from expensive or hard to find components
-I really don't like having bare PCBs dangling out of my machines
With these thoughts in mind I decided to leave the expansion port alone and see if I could make a board that would fit in place of the Z80 as (nearly) all the required lines should be there and DIL-40 sockets aren't exactly rare.
The only required line that I'm aware is missing at the Z80 is the Audio-in to be found on Pin 31 of the expansion connector, so that will have to be a flying lead - either to be soldered somewhere suitable or as a separate line-out.
(As an aside when I did a Mockingboard clone for my Apple IIs I made sure to keep the dual AYs outputs separate for stereo but as the ADAM has only one audio-in that I know of this early prototype is mono)
I've attached screen-shots of my first attempt at a schematic and PCB layout. I should point out I'm aware space around the Z80 is a bit tight and so far I've only eye-balled it for space...
...um, I'm also very new to the ADAM so the schematic may have some serious errors. I'd welcome advice and suggestions if anyone has them to share.