[sdiy] New TOG board: $0.02 needed

[Scott Gravenhorst]

Scott Nordlund <gsn10 at hotmail.com> wrote:
>
>I've always wanted to retrofit a TOS-based synth with something 
>that output Walsh functions instead of simple 2'/4'/8'/16' 
>squares. Of course this would require all the octave dividers to 
>be replaced (with CPLDs?) 

IMO, an FPGA would be more appropriate, lots more logic to play with.  Then you can go completely
nuts with the design.  Also, a CPLD has no dedicated multipliers, AFAIK, a Walsh synth would need
multipliers so that each logic output can be amplitude controlled rather than simply on/off.  An
FPGA has this capability.

>and some more complex mixing, but I 
>think it would be a nice alternative to the relatively boring 
>square/pulse (and occasionally saw) waves. 
>
>I'm sure this is probably a bit beyond the scope of what you're trying to achieve, though.

Yes, actually I think what he did, putting a whole TOG in one CPLD is remarkable enough.

>----------------------------------------
>> Date: Tue, 6 Jan 2009 13:26:06 -0800
>> From: madhun2001 at yahoo.com
>> Subject: Re: [sdiy] New TOG board: $0.02 needed
>> To: synth-diy at dropmix.xs4all.nl
>>
>> Inline code follows...
>>
>> --- On Tue, 1/6/09, Tim Parkhurst  wrote:
>>
>>> - Output pulse width option / modulation. I know it would
>>> be difficult to
>>> maintain a specific pulse width in the divided-down
>>> octaves, but it's not
>>> impossible and might be a nice timbral option, even if it
>>> was just a 50% /
>>> 75% option or something like that.
>>
>> I can easily make a version of the VHDL code that produces 
>other than 50% duty cycle. I believe a version of the 50240 had 
>37% duty cycle. > >> - Option to add internal squares together to 
>create saw-ish >> output >> waveforms. Worked pretty well for the 
>ARP Little Brother >> ;-) Could be cool >> to create an octave of 
>saws, and use one of your CPLD >> boards for each octave >> 
>(rather than dividing down for subsequent octaves). > > I have a 
>board being fabbed that has dividers and resistor chains to make 
>sawtooths. Another board, also in fab, does sine waves. > >> - 
>Output for chaining together several of your boards, as >> 
>mentioned above, >> one for each octave. This may be what you've 
>already >> done with the seven >> stage divider. > > The on-board 
>divider allows for that, although it is cheaper to do post 
>dividing of the octaves. Got a board for that as well... > >> Tim 
>(not sure what my 2 cents is worth) Servo > > Way more than $02. 
>Darned inflation... > > --TimR > 
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-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
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