AW: AW: [sdiy] AD/DA schematics? quantizers,etcy

[David G. Dixon]

Dan,

For a decent clock, I've used a simple relaxation oscillator (basically an
opamp, three resistors and a capacitor).  This is also, I believe, the style
of clock used in ARP quantizer circuits.  I can't see why this wouldn't work
well for your application.  This sort of device would easily go to much
higher frequencies than a VCO.  The frequency limitation is probably the
slew rate of the opamp (considering the rail-to-rail swing), which could be
addressed by using a proper comparator, although for this sort of
application, this should be strictly unnecessary.

> i have had NOTHING but trouble finding a clock that is both stable and
> will go high enough
> 
> 
> i am finding 2 things...that for driving this with AUDIO i need a very
> high clock (neither of my  vcos go anywhere near high enough)
> and that for the quantizer i get some results with my vcos but would
> probrably get better with a clock rate specified in the datasheet
> 
> 
> anybody have schematics for a really high freq clock? maybe even a a
> voltage controlled one?
> 
> or do i just need to switch the cap of a vco to a really low one like a
> 50pf?
> 
> anyway...this has been a great learning experience.
> 
> even if it only sounds like a sample and hold at this point, it IS in tune
> when i move my offset pots correctly.
> 
> 
> anyway...i am sure i will be writing more later !
> 
> thanks
> 
> 
> 
> >
> >> Von: synth-diy-bounces at dropmix.xs4all.nl
> >> [mailto:synth-diy-bounces at dropmix.xs4all.nl]Im Auftrag von Dan Snazelle
> >> Gesendet: Freitag, 15. Mai 2009 17:38
> >> An: jerryge at cableone.net; sdiy
> >> Betreff: RE: AW: [sdiy] AD/DA schematics? quantizers,etc
> >>
> >> ok
> >>
> >> in the current setup, the quantatizing (sp?) seems to be working
> >> better BUT and this is a big BUT....
> >> When DRIVING a VCO....it is sounding more like a sample and hold
> >> than a quantizer.
> >>
> >> and what i mean by this is that if i feed in a very low freq
> >> sawtooth what i get out of the vco sounds like a series of notes
> >> with steps in between very very similar to a sample and hold fed
> >> by a white noise and fed into a vco
> >>
> >
> > 1st thing that comes to my mind is: you wired the input bits of DAC in
> the
> > wrong order.
> >
> > if wired correctly you should see a staircase as result of your
> sawtooth.
> > the datasheet should give you a table that shows the combination of the
> bits
> > resulting in what output voltages.
> > i.e. 0100000 for 0.04V and 01111111 for 9.96V (7 bits used, 10Vref). so
> what
> > would 01001100 be? you should verify that.
> >
> > hope i did not misunderstood the whole issue!?
> >
> > cheers,
> > matthias
> > ___
> > www.fonitronik.de
> >
> >
> >
> >>
> >>
> >> is this due to what fonik was mentioning? he noted that he needed
> >> to put latches on the output of the DAC so that there was a
> >> smooth flow between notes
> >>
> >>
> >> or maybe i have done something wrong again
> >>
> >>
> >> all in all it is a cool sounding effect but not quite the sound i
> >> had been going for.
> >>
> >>
> >> i do not know even how to setup a latch on the out...what would
> >> control it?
> >>
> >> the clock? a bit from the A to D?
> >>
> >> thanks
> >
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