Unveiling my second project

  • This Monday I'll travel to Barcelona. I'll take this oportunity to acquire new components (do you believe it? I have a lot of 32K SRAM, but no 128K ones! ). As I don't know how much time wil pass until I could travel again and acquire more components, I'll try to get enough material to cover as many projects expected to take place during Summer.


    So I think it's time to present an idea I've been coving since January, when I (accidentally) found a MC-16 schematics scan. The MC-16 was the first sound card the Apple ][ had, and (I may be wrong) it was maybe the first commercial sound card a microcomputer had.


    Examining the diagrams I learnt some things. First, that a simple soundcard contains two sections: an analog one containing an operational amplifier, DACs to control the volume of each voice and resistors to mix the different voices; and a logic one which is a programmable signal generator. In the case of the MC the signal generator is a 8253 PIT, which was made as a support chip for the 8085. The original PIT is not made anymore, but the 82c54 is still in production and they are compatible.


    About the name of this project:

    I decided to name it "Shakuhachi". A shakuhachi is a very simple vertical flute made of bamboo.


    Image courtesy of Wikimedia commons.


    Just that, a bamboo pole with some holes. And the MC is just a counter with some DACs... Do you see the simile? :)


    This project is sure that won't be finished during Summer (so no false expectations). But the goals are the following:

    #1: Clone the design, adapted to use modern-day components

    #2: Experiment the following designs:


    square.jpg

    Square wave


    pulse.jpg

    Pulse


    sawtooth_inversesawtooth.jpg

    Sawtooth/Inverted sawtooth


    Triangle

    #3: If (#2) successful, think about integrating as much as possible in a card.


    Thank you for your time and my apologies for such ugly and dirty drawings.

    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol:

  • this is a joke isn't it?


    Stefan



    No, it isn't. I forgot to mention that it is not an Apple ][ project, but a P2 one. While I had not seen this other thread, I see it makes use of the old DACs which I'll try to replace.

    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol:

    Edited once, last by jlopez: Ortography ().

  • So , in that case sorry about my doubts.


    Stefan

    Why did you thought I was joking? ::cry::

    After I found the schematics I made some research and found other computers (mainly Russian clones of other systems) implementing sound using the same approach. Why Russian clones can have some good audio and my poor old P2 just a beeper? That's not fair!


    Don't worry, after all it's a hobby and everything here is just for fun and for learning purposes. :)

    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol:

  • Hello


    I have a first version of the design, using common parts and adapted to the 96-pin bus of the P2. At first glance it can be seen that an entire byte of the address is unused, so in case of a wirewrap the area near the connector wouldn't be as crowded as the memory card was.



    The analog part is still to be drawn, I have never worked with DACs or OPAMPs. I think I'll use DAC0800 but I don't know about the replacement for the LM307... I'm going to do some good research to find suitable present-day replacement.


    This is enough to add some ICs to my BOM list.


    Thank you very much,

    Jaume

    When I tried to list all retro systems I have at home, the "The message is too long, must be under 500 characters" error appears! :lol: