[sdiy] VCO waveform logic selection

[harrybissell at wowway.com]

No the signals in the Prophet V do not remain positive
at all... they are bipolar.

The small voltaes at the summing junction are way below the
didoe drop (-0.7) and you might think of them more as currents
rather than voltages...

H^) harry


On Wed, 12 Sep 2007 18:11:28 +0100, Tom Wiltshire wrote
> On 12 Sep 2007, at 12:29, René Schmitz wrote:
> >
> >> On your webpage you note that the diodes may not be omitted.
> >
> > Read that as "should".
> >
> >> Are the protection diodes built into the device inadequate for  
> >> this purpose?
> >
> > Those diodes delimit the amplitude to +-0.6V around GND, while the  
> > input protectors do clamp against Vcc and GND. Delimiting the swing  
> > at the open switch does reduce the risk of capacitive crosstalk.
> 
> I note that on the Prophet 5 schematics, the switches are Quad SPST  
> 4016's, and are handling control voltages which presumably remain  
> positive (0-5V, most likely) since there is only a single diode to  
> earth.
> 
> Thanks for bringing this up, I hadn't studied this part much before. 
>  Fascinating!
> 
> T.
> 
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Harry Bissell & Nora Abdullah 4eva