[sdiy] [spam] Re: Pink Tunes self-composing program.

rsdio at audiobanshee.com rsdio at audiobanshee.com
Tue Jan 9 08:37:12 CET 2018


Thanks for the hint, Terry.

I found the following to be very informative
http://www.muzines.co.uk/articles/paia-8700-computer-controlle/2614

The PAiA 8700 has a 6503, which is a 6502 with a reduced address bus. The DAC uses only 6 bits, so exponential would make sense as the only feasible utility for a mere 64 distinct output levels. There is 1 bit used to control glide between output levels, and I assume that would be an analog glide. There is also 1 bit used for Gate. In total, 8 bits are output to control the transition to a new level.

I’d like to see a more detailed schematic for the QuASH component mentioned, but I suspect that if I read through the assembly source code then I could learn what I need. If such a schematic is available, then the exponential nature of the DAC could probably be confirmed.

Thanks again,

Brian


On Jan 8, 2018, at 3:03 PM, KA4HJH <ka4hjh at gmail.com> wrote:
> On Jan 8, 2018, at 5:54 PM, Jay Schwichtenberg <jschwich53 at comcast.net> wrote:
>> Hard part is figuring out what all the hardcoded numbers are. For example are the music keyboard values directly related to a real note voltage value? Initially I'm going to assume that is true.
> 
> IIRC, Pink Tunes was written for the 4700 system which used a custom exponential DAC with linear VCOs. If so the output pitch values should all be linear.
> 
> Terry Bowman, KA4HJH
> "The Mac Doctor"




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