[sdiy] Walsh update

[Scott Gravenhorst]

music.maker at gte.net wrote:
>"John L Marshall" <john.l.marshall at gte.net> wrote:
>>Magnus,
>>
>>It seems that you would want each note within an octave and each octave to
>>have the same timbre. But, with the walsh generator you would want to freely
>>manipulate the timbre, maybe through time. How are going to do that?
>>Wouldn't it be cool to convert from Walsh to sine series and have sine
>>octave draw bars?
>
>This is a cool idea, it would be very conventionally intuitive 
>performance-wise.  
>
>Has anyone got any mp3 examples of what happens when one Walsh
>coefficient is varied?  Would it be as useful to have Walsh
>coefficient controls at the front panel as it would sine type
>drawbars?
>
>>The Walsh series would be longest for the lowest octave of notes but be very
>>short for the highest octave unless your TOG is 32 or 64 times the highest
>>note to be played.
>
>PLLs on each of the TOG outputs could track and frequency multiply
>the 12 pitches.  Lot's of parts though, at least two ICs per note.

I might add here that a modulation signal can also be applied.
I found that a PLL tracking a pitch can be nicely vibratoed by
injecting an LFO signal mixed with the loop filter output feeding
the VCO input.  Again, lots of parts, but a separate LFO for
each pitch would give a fair amount of character.  Though as I
said, it would be a whole mess of parts.  In the end, perhaps
12 discrete oscillators with analog harmonic generation make the 
most sense in terms of building.

>>Take care,
>>John
>>
>>----- Original Message -----
>>From: Magnus Danielson <cfmd at swipnet.se>
>>To: <madhun2001 at yahoo.com>
>>Cc: <synth-diy at dropmix.xs4all.nl>
>>Sent: Sunday, March 24, 2002 5:29 AM
>>Subject: Re: [sdiy] Walsh update
>>
>>
>>> From: Tim Ressel <madhun2001 at yahoo.com>
>>> Subject: [sdiy] Walsh update
>>> Date: Sat, 23 Mar 2002 15:44:01 -0800 (PST)
>>>
>>> > To all,
>>> >
>>> > AS you might have noticed, I kinda got distracted by
>>> > this little midi project. No, I haven't forgotten
>>> > about the Walsh thing. The board layout is done except
>>> > for checking. I am planning on sending the board out
>>> > for fab real soon now. The CPLD design has been done
>>> > for a while, its time for me to do the next part.
>>> >
>>> > <------------------------------------------------>
>>> > In the spirit of the list, does anyone want to
>>> > volunteer to check the layout? I can mail a package
>>> > with all the docs. Don't have my PDF writer yet, so it
>>> > has to be snail-mail.
>>> > <------------------------------------------------>
>>> >
>>> > This board will just be a breakout board for the Walsh
>>> > CPLD. I have provided for both molex-style connectors
>>> > (0.1") and dual-row header for ribbon cable. You can
>>> > also populate the connector pins with machine SIP
>>> > sockets to accept 24 ga solid wire.
>>> >
>>> > This little kit will consist of board, CPLD, and
>>> > socket. Price will be in the $20-$25 range depending
>>> > on how much the boards cost me. I'm not trying to get
>>> > rich here, just trying to cover my costs.
>>> >
>>> > I will let you know when the stuff is available.
>>>
>>> Question:
>>>
>>> Why do you need a CPLD?
>>> You can create any size of Walsh generator with a frequency divider
>>> and a handfull of XNOR gates. For a organ setup, all you need is the
>>> TOG part and 12 Walsh generators.
>>>
>>> Maybe I should do a simulation and hand it out.
>>>
>>> Cheers,
>>> Magnus
>>
>
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>-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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=========================================================  
- Government: The other religion.
- The media's credibility should always be questioned.
- Lambs who lie down with lions are lunch.

-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
-- Linux Rex         | RedWebMail by RedStarWare
-- FatMan: home1.GTE.NET/res0658s/FatMan/index.html
-- NonFatMan: home1.GTE.NET/res0658s/electronics/index.html