[sdiy] New TOG board: $0.02 needed

[Tim Ressel]

FYI:

Cheap digital pot: MCP4231-103E/P-ND (DigiKey)
Dual 10K (other values available) $0.68 in 100 pcs

That's $0.34 per pot. Not bad. 12 notes * 8 Walsh coefs per = 96 pots = $32.64. 

Another cool thing: since all notes will have the same timbre (?) the digital pots can be tied together and all clocked at once.

Of course that is going to be one nightmare board to lay out....

--TimR


--- On Tue, 1/6/09, Nicholas Gregorich <nicksdsu at mac.com> wrote:

> From: Nicholas Gregorich <nicksdsu at mac.com>
> Subject: Re: [sdiy] New TOG board: $0.02 needed
> To: music.maker at gte.net
> Cc: synth-diy at dropmix.xs4all.nl
> Date: Tuesday, January 6, 2009, 8:08 PM
> Scott Gravenhorst wrote:
> > 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.
> > 
> 
> If you control amplitude in the FPGA then you need a DAC
> (rather than just an output pin) and a way to control the
> amplitudes (MIDI or ADC).
> 
> I think part of the beauty of a Walsh generator is that you
> can actually put it in a small CPLD and build a mixer,
> that's it. No development kits  needed.
> 
> Nicholas
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