[sdiy] Old Computers

[Ken Stone]

Back before sound cards were popular, there were instructions on how to make
an 8 bit d/a dongle for the parallel port so you could play music. It wasn't
bad. There is no reason why a 16 bit one couldn't be done, using a couple of
the different strobe/select lines to latcht he two DACs. Have a look at my
web page in the "other projects" section for a rather more complex parallel
port adapter. The info there may be of help.

Ken

>With the introduction of AVRSYN, I remember a post not that long ago by
>someone asking if anyone had attempted to use an old PC to make some kind
>of synth.  I have several of these myself, 486-66 and AMD 5x86-133.  I did
>a little bit of research and found a website where someone had done a DSP
>using a soundcard and a special 16 bit DAC ISA card that he designed (this
>is because, according to his information, a Creative SoundBlaster does not
>allow a program to directly send values to it's 16 bit DAC and there are
>only one 8 bit and one 16 bit DMA channels, but 16 bits was required for
>both input and output).  My sound cards are all Creative devices and I'd
>prefer the simplicity of being able to directly manipulate the DAC.
>
>So I looked at Jarek's site and I see he uses a homemade 16 bit DAC, driven
>by 2 CMOS latches.  I wondered why we can't do the same with a printer
>port.  That totally removes the need for a soundcard altogether and the
>"dongle" would be extremely simple and trivial to program.  PCs have a
>built in programmable interrupt timer that can be set to interrupt
>regularly and an interrupt service routine could then calculate the next
>DAC value and present it.
>
>Has anyone approached this at all?
>
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_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
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