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Put the output of you Poly 800 into a scope and you will
see that your Poly will never output a square wave, looks
more like a fuzzy saw wave, anyways, finding a way to
modulate the wave shape will be of great value, sure thing.
if this is being discussed, any plans to add pulse width?
(to original DCO)
eg: if the square is produced by a comparator, varying the
input compared to will vary the pulse width. maybe
simething similar is possible here?
--- In korgpolyex@yahoogroups.com, Michael Hawkins wrote:
>
> Gordon,
>
> I want to be able to digitally control the oscillator variation of DCO2. Digital
> control also might mean using a D2A or use an analog control. Or even a digital
> pot.
>
> But the goal here is to be able to vary the frequency of DCO2 which gets its
> "master" rate from the master clock. The master clock will continue to be sent
> direct to DCO1. And the MG and joystick bend will also continue to vary the
> master clock rate (thus giving both DCO1 and DCO2 the same MG and joystick bend.
>
> So I want to continue to use the original Poly master clock but want to insert a
> new DCO2 "detune" that has far more frequency variation and far more granular
> control than the current detune.
>
> I seem to remember from my electronic engineering classes (that would be 15
> years ago now) that a phase locked loop (4066?) might be the way to do this.
> Does anyone have experience with PLL's for generating frequencies that are
> slightly varied from the input master clock?
>
> Mike
>
>
>
>
> ________________________________
> From: Gordon JC Pearce
> To: korgpolyex@yahoogroups.com
> Sent: Mon, July 18, 2011 2:17:47 PM
> Subject: Re: [korgpolyex] DCO2 detune
>
>
gt; On Mon, 18 Jul 2011 00:55:06 -0000
> "korgpolyex800" wrote:
>
> > Can anyone suggest a way that I could produce a slightly offset oscillation
> >based on a master clock source? And that slight offset could be adjusted using
> >digital or analog signal voltage technique?
>
> Not easily, but you could use a crystal oscillator with a varicap diode to pull
> it a few kHz. I don't know if that would get you the range you're looking for.
> Some radios use a transistor and a capacitor to shift the CPU clock a bit. That
> way, if a harmonic of the clock oscillator will cause interference to a
> particular channel you can move it out of the way. I'll see if I can scan in
> the relevant page of a manual that shows this - I know the Motorol MC Micro has
> this, so if you find a PDF you can maybe do something with that.
>
> I f you really wanted to go nuts with it, you could use a DDS chip.
>
> Gordon MM0YEQ
>