Thanks, canthearu. I'm glad that you could appreciate the main bb's feature.
a) Different CD-ROM manufacturers (Sony/Mitsumi/Panasonic) has different analog out pinouts. The idea was - with my cable you can rearrange the pins as your CD-ROM requires and connect it to this single 3-pin header on the board. Otherwise there should be at least three 4-pin headers only for CD, but there is no space for that:) The included cable works fine, despite it is not shielded.
I would say stick to the most standard (Right - Ground - Ground - Left) that would work with the vast majority of IDE drives. But of course, this is not major, mearly me nitpicking.
CD amplification depends on your CD-ROM's output level. The amp was designed with a reference input of the most quiet of 3 CD-ROMs I have. I met some models whose rear analog output was dependent on the front volume regulator as well.
You also can add the CD gain by changing R32 and R33 from default 33k to 27k or 22k. I do not recommend going lower than 15k.
Thanks for the tip. For this particular drive, the gain is not too low, but I have to crank it much further up than the WAVE/OPL2 channels. Again, me totally nitpicking 😀
b) An ability to program ATmega onboard is fancy, but it requires significant changes and complication of the schematics - adding secondary MCU which will communicate with ISA bus and program the main MCU + some pin multiplexing logic. I will implement this ability in my next project which is now in a prototype development stage and is too early to talk about 😉
Yeah, if it requires a redesign of the board to add extra ICs and such, then not worth it. If it can be reprogrammed over the ISA bus with either all software, or only minor hardware changes, then I think you should pursue it.
c) I should check this out.
Would really depend if the C/MS is controlled on the same I/O ports as the WAVE/OPL2 chip, and how much horsepower you need in the ATmega to create a passable copy of the C/MS sound chips. Of course, it could never be stereo like I think the original C/MS was, but I doubt any software really took advantage of it.