Walsh Function Primer

[Tony Allgood]

Hi folks. This walsh function thing is really hotting up. To generate the
high frequency needed I used a CEM3340 with a smaller cap than usual.
Tuning wasn't a problem, but I was only using it monophonically, it may be
worse if you were to mix it with another VCO.

I'm sure there was a Digisound module that used a high frequency CEM to
drive an EPROM with no problem. However, it may be a good idea to use a
PLL, especially if you need to generate a lot of wal and sal outputs!

And remember, you need to use a tracking filter to iron out the nasty
staircase waveform you get when you add those rectangular babies together.
I used a SSM vcf, it worked a treat. Shame my digital EG didn't work. Long
live the ADSR!!

Tony

----------
> From: Neil Johnson <Neil.Johnson at camcon.co.uk>
> To: Martin Czech <martin.czech at itt-sc.de>; synth-diy at horus.sara.nl
> Subject: Re[2]: Walsh Function Primer
> Date: 05 August 1997 8:56 AM
> 
>      Martin (and list),
>      
>      I use a digital oscillator to generate the clock signal.  This is 
>      controlled by an 8051 microprocessor using a pitch table:
>         note + pitchbend + mod -> TABLE -> 24 bit number -> Oscillator
>      
>      For frequency modulation you could hook up an ADC to the micro and
get 
>      it to read the ADC every, say, 1ms and add that value to the pitch 
>      number.  Then you can feed any signal into the ADC (EG, LFO,
joystick, 
>      etc) and modulate the pitch.  As long as you don't want AF
modulation 
>      you should be alright up to a few hundred Hz modulation frequency.
>      
>      Neil
>      ----
>      
>      
>      
>      +---------------------------+-----------------------------+
>       Neil Johnson               * All thoughts and opinions
>       Cambridge Consultants Ltd  * expressed here are my own.
>       email: nj at camcon.co.uk     * Heck, even _I_ don't believe
>       http://www.camcon.co.uk    * what I say at times.....
>      +---------------------------+-----------------------------+ 
>      
> 
> 
> ______________________________ Reply Separator
_________________________________
> Subject: Re: Walsh Function Primer
> Author:  Martin Czech <martin.czech at itt-sc.de> at Internet-PO
> Date:    05/08/97 08:23
> 
> 
>      
> Thank you for your interesting explanation. 
> (No irony here).
> I once learned, that synthesis could be done 
> with a lot of orthogonal functions, but the name Walsh 
> never was heard.
>      
> But one question remains : 
> How to get a rather high clock frequency for the generator? 
> Precision VCO work at 20Hz-20KHz, and at the top end there are 
> already difficulties with delays etc.
> Flat tracking. How to create frequencys
> say 128 times higher, without using a pll or a divider?
>      
> How do you do this?
>      
>      
> m.c.
>