[sdiy] Old Computers

[Scott Gravenhorst]

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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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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