[sdiy] Walsh Generator & demo board

[Tim Ressel]

Tony,

What I did was to "borrow" the summation scheme from
Scott Gravenhorst's Complex Waveform Generator for the
Paia Fatman. It seems to work just fine. A coupling
cap on the output takes care of the DC offset.

http://machines.hyperreal.org/manufacturers/Paia/Fatman/mods/complex.waveform.generator.gif

--TR

--- Tony Allgood <oakley at techrepairs.freeserve.co.uk>
wrote:
> Hi Tim and All,
> 
> >It takes a clock in, and produces 15 sin and cos
> Walsh functions. I am
> considering offering it for sale, along with a
> little demo PCB which has
> a 8 (or more?) input mixer for summing the Walsh
> functions.
> 
> First thing that you should know is that the walsh
> outputs need to be
> bipolar. Or at least mixed in a fashion so as not to
> allow the sumnation
> of the wal outputs to affect the DC offset. So just
> summing TTL type
> square waves wrt ground is not going to work
> properly.
> 
> Second thing, is that the mixer should be a
> reversible attenuator type.
> Many types of waveforms, symmetrical ones about OV
> IIRC, use some
> inversed wal outputs.
> 
> Third thing is that for bass notes to take on any
> real power you really
> need 31 walsh outputs. I found 15 not as interesting
> and a little
> 'electronic'.
> 
> But you know the biggest problem with any walsh bank
> is not the
> generation of the walsh series. This can be done
> pretty simply with
> about eight or so cheap HCT chips. The problem is
> mixing them, and
> controlling the pitch over a decent musical range.
> 
> Still think that all of this needs to be done in
> software as a virtual
> synth.
> 
> Regards,
> 
> Tony Allgood                       Penrith, Cumbria,
> England
> 
> Oakley Sound Systems                    
> www.oakleysound.com
> Modular projects           
> www.oakleysound.com/projects.htm
> 
> 


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