[sdiy] Walsh Generators

[Mark Smith]

One of my early projects playing around with square waves and high speed osclillators was a idea not do dissimilar to the walsh principle - only much less hardware.

It involved dividing down from the input frequency using flip flops and then summing them using different co-efficients. To make it simple I wrote an excel spreadsheet to display the output waveform and then chose 4 inputs into the mix stage and 4 mix levels that were programmable. This gave 256 waveforms from saw to square with lots of different stepped square and saw waveforms in between. The resolution of the saw was 256 steps if I remember which came out pretty good. The idea failed slightly oin the fact that I couldn't get a processor to drive the input clcok high enough - maybe a high speed vco would help - or I could use a saw input and then multiply it up...

http://www.meadowfield.freeuk.com/synth/dig_osc.pdf
 
heres the schem and some pictures of the pcb, if anyone is interested in the excel file I'll try and dig it out.


cheers

mark


> -----Original Message-----
> From:	owner-synth-diy at dropmix.xs4all.nl [SMTP:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Terry Ahrens
> Sent:	Friday, March 18, 2005 3:35 AM
> To:	Aaron Lanterman; synth-diy at dropmix.xs4all.nl
> Subject:	Re: [sdiy] Walsh Generators
> 
> Aaron Lanterman <lanterma at ece.gatech.edu> on Thursday, March 17, 2005 at
> 7:04 PM  wrote:
> 
> I've been working on a project to do just that, and clock it from an
> oscillator. If it has eight steps, the ouput will be three octaves below
> the oscillator, at sixteen steps it will be four octaves below.  I'm
> thinking that adding a tiny amount of slew may have a beneficial effect. 
> But if others have tried this and abandoned the idea, it must not be as
> interesting as I was hoping for.
> ~Terry
> 
> >> There were a number of experiments with using sliders to 'draw'
> >waveforms
> >> directly...
> >
> >I remember in the electronic music lab at Wash U, I once took the
> >sequencer on the 2500 and clocked it at audio rates. You could get some
> >wild sounds that way - it was weird hearing it shift from individual tones
> >or amplitudes into a totally new sound with a pitch at the rate you were
> >clocking it at. I remember modulating both the VCA and the VCO with it.
> >
> >- Aaron
> >
> >-----------------------------------------------------------------------------
> >
> >Dr. Aaron Lanterman, Asst. Prof.       Voice:  404-385-2548
> >School of Electrical and Comp. Eng.    Fax:    404-894-8363
> >Georgia Institute of Technology        E-mail: lanterma at ece.gatech.edu
> >Mail Code 0250                         Web:   
> >users.ece.gatech.edu/~lanterma
> >Atlanta, GA 30332                      Office: GCATT 334B
> >
> >
> 
> 
> 
>