[sdiy] Walsh Generator & demo board

[Scott Gravenhorst]

I just looked at it again and I notice that if you
power the CMOS parts at +/- 9v (or less), the CMOS
outputs become bipolar.  Then, a simple pot from
the CMOS buffer output to ground forms a voltage
divider that then outputs the bipolar signal
at any level.  The pot could be a VCA instead to
allow voltage control.  Doing it this way eliminates
the 4 opamps, and all the resistors and at least
most of the DC offset.  If one of the regulators for
this is adjustable, the remaining offset should be 
easily eliminated.  I imagine that +/- 9 v should
also work for the opamp.

Also, I would not use 4049 or 4050, as a buffer, rather 
I would use the 4069.

So if the Walsh generator you have is CMOS based, this
may work for you and simplify it.



Tim Ressel <madhun2001 at yahoo.com> wrote:
>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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