[sdiy] Digital Synth Module ideas ...

[Andre Majorel]

On 2006-09-04 11:07 +0100, Seb Francis wrote:

> Andre Majorel posted some samples recently of what it sounds like doing 
> various bit-swap operations (link anyone?).  Unfortunately again mostly 
> ugly digital distortion.

That would be http://www.teaser.fr/~amajorel/aubitswap/. It tends
to be UDD(tm) when you swap low-order bits with high-order bits.
Swapping adjacent high-order bits gives more musical spectra. For
example, try swapping bits 13 and 14 on a full-scale sine. There
are sound samples on the page.

In general, the resulting spectrum is very sensitive to the
amplitude of the input signal so it's definitely worth trying it
post-VCA.

For a hardware implementation of bit swap, I would use an ADC and
a DAC back-to-back with a patch panel between the two, say 12 jack
sockets for the top 6 bits. It's intuitive and it opens the
possibility of doing bit-bashing with external logic modules like
the CGS26 and CGS39. IMO that would be a better interface than
anything you might achieve with a micro-controller and a bunch of
buttons and LEDs.

  http://cgs.synth.net/modules/cgs26_analogic.html
  http://cgs.synth.net/modules/cgs39_quad_gate.html

> P.S. Andre, what software did you use to do the bit-swap stuff?  I have 
> cygwin installed, so I'd like to try out some of these ideas before I 
> bother coding them in assembler!

The source code is on the page. It's C++.

If you need the other utilities (auamp, auplot, ausin etc.), I'll
give you the whole source. They should all be portable except for
ausink and ausource (audio I/O) which depend on OSS. Everything
else is a raw PCM. Trivial to convert to and from WAVE.

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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