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Thread: Creative Music System / Game Blaster clone

  1. #21
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    I've managed to install a 10k pot on it, hanging from a few wires. It's not pretty, but I can control the volume, and the distortion was probably coming from the speakers and/or the amp being too loud.
    Initially I was missing some sounds, it seems, but I swapped the SAA1099s for some others, and now it seems perfect!
    So either I have a dodgy SAA1099, or it wasn't seated in the socket properly. I'll have to do some more testing, but I want a pot that fits properly first I ordered some online, they should arrive any day now. Hopefully these will fit

  2. #22
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    Glad you were able to get the card working and the distortion issues under control. If your SAA1099s came from eBay it is possible that they were pulled from other devices and it is certainly possible to end up with a bad chip that way - or it could just be a bad connection in the socket or a questionable solder joint somewhere as well.

    Hopefully you can find a pot that fits within the height constraints of an ISA card/slot. If I had it to do over again, I would have made sure I had an appropriate sized pot on hand before getting the boards made.

  3. #23
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    Well, the pots I got were indeed too high, so I ended up mounting them in reverse. Sadly, this also reverses the audio taper, so they're really touchy at low volume now. If I just went with linear I wouldn't have had that problem, heh.
    Nevertheless, it works:


    And yea, those Bourns PTD90 series would probably have been the perfect size. Perhaps you could update the PCB schematic so that the pinout matches to them? Then if anyone orders another batch, that problem is solved.

    One thing I wonder though: where the heck did Creative and others get those 'dial' type pots they used on the Game/Sound Blaster cards? I could not find any of those anywhere.

  4. #24
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    I did a bit of a hack, which turned out ok:
    I took a smaller pot, used the front-middle pin through the PCB, and bent all the others so that they could be soldered on top of the PCB.
    The result is actually quite nice, and the pot is now accessible from the back of the PC
    WP_20171209_15_06_13_Pro[1].jpg
    This is what I would recommend others to do as well.

  5. #25
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    Very nice!

    Is the output stereo? Can't tell from the video.
    Offering a bounty for:
    - A working Sanyo MBC-775
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)
    - Any very old/ugly IBM joystick (such as the Franklin JS-123)

  6. #26
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    The output from the card is in stereo. It should be just like the original Creative card unless Creative did something odd like swap the left and right channels or something like that.

  7. #27
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    Quote Originally Posted by Trixter View Post
    Very nice!
    Thanks! Veovis did a nice job on the PCB!

    Quote Originally Posted by Trixter View Post
    Is the output stereo? Can't tell from the video.
    It sure is!
    I am currently trying to code a routine to play PCM samples. If that works, you can get stereo digital playback from any SB 1.x/2.0

  8. #28
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    Quote Originally Posted by Scali View Post
    I am currently trying to code a routine to play PCM samples. If that works, you can get stereo digital playback from any SB 1.x/2.0
    If you're successful, we should contact the author of Galaxy Player and try to get him to release the source so that we can complete it based on his promise.
    Offering a bounty for:
    - A working Sanyo MBC-775
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)
    - Any very old/ugly IBM joystick (such as the Franklin JS-123)

  9. #29
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    I have discovered some 'interesting' behaviour:
    With the Game Blaster clone, my IBM Music Feature Card could no longer be detected.
    Now, I know the detection routine for the IMFC works by writing a value to a latched register on the card, and reading it back to see if it 'stuck'.
    So I tried doing that manually. I noticed that if I wrote 'FF' to it, it read back as '7F'. So apparently the top bit got 'eaten' somehow.

    Now, the IMFC has a base address of 2A20, and this particular register is at 2A21h.
    My Game Blaster clone was set to a base address of 220h, so it would use the range 220h-224h. If the card does not fully decode the address, then it may 'mirror' itself in the 2A20h-2A24h range as well. So it may be interfering with the IMFC, causing the issue I had.

    So first I pulled the Game Blaster, and the IMFC was detected properly again: writing and reading FF was no problem.
    Then I reconfigured the Game Blaster to a base address of 210h, and put it back in. Writing and reading FF was no problem... however, the second test is to write and read 0.
    Doing this yielded 'E5' when reading back.

    Any thoughts on this? I mean, is this actually a bug, or is the original Game Blaster designed like this? And do we want to fix this, or simply accept that it is what it is?
    It would seem that most cards are in the 200-3FFh range of ports. The IMFC is actually the only card I've ever encountered to have an address like 2A20h (using 14 bits rather than just 10). Perhaps most cards treat any address bits above the 10th bit as 'don't care'?
    There may be many other cards that have the same issues.
    Last edited by Scali; December 17th, 2017 at 03:28 AM.

  10. #30
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    What you are seeing does make sense. My clone only decodes up to A9 which allows for address up to 0x3FF which I believe is the official upper bound for expansion card IO addresses for IBM 5150 and 5160 PCs at least.

    I didn't realize that decoding the other address lines may be necessary - especially since the few address decoding examples I could find only went up to A9. Decoding the other address bits would probably require adding a few more logic chips.

    I don't think I have ever encountered a card that went beyond 0x399 before. It would be interesting if someone with an original Game Blaster or CMS could look at their card and see if the address lines above A9 (A10 through A19) are connected to anything. I would be surprised if they are but who knows.

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