Osc reset time

[Fraser, Colin J]

> -----Original Message-----
> From: Haible Juergen [mailto:Juergen.Haible at nbgm.siemens.de]
> Sent: 17 December 1998 12:36
> To: JH; DIY; Fraser, Colin J
> Subject: AW: Osc reset time
>  
> 	> Do you know of anywhere I might find a schematic of such an expo
> convertor ?
>
> Korg Polysix, for example. (It's multiplexed for all 6 voices,
> but the basic principle is there.)

Should have rememebered that - I have the service manual somewhere.

> Now the general drawback of these linear VCOs was that
> you *had* to make the footage switching, because if you
> wanted to cover the full range with one expo CV you came
> in conflict with offset voltages, and more important, offset
> voltage drift.
> My assumtion (still untested) is that we would have much less 
> trouble today with low offset opamps. I think that it would still
> be difficult to cover ultra low LFO range and audio range with
> one CV, but audio range down to fast LFO range might work.
> (It does in my Frequency Shifter VCO, but then I have only
> built one single unit.)

Let's hope so - I will test this over the weekend, assuming Maplin have a
411 in stock !

> 	> And what sort of impedance does a typical current 
> source have ? 
> 
> Depends on how you build it. from 100s of kOhms to 100s of
> MegOhms if you build a cascode. But that wouldn't interfere
> with the switches' on-resistance, anyway, would it ?

I don't know - the on resistance is specified for a given load resistance.
I'm not sure what sort of interaction there might be.
I guess experimentation will tell.

One more question for now - what would be the benefits of thru-zero FM ?


Colin f