The Magnus phase shifter

[Ian Fritz]

There is a nice discussion of this kind of V/F converter in W. Jung's "IC
Op-Amp Cookbook", including derivation of the design equations and a couple
of examples using the RC4151 / LM331. (Note that pins 3 & 5 are reversed in
Fig. 10-28.) I calculate that the Chroma reset time is 33us. Very accurate
frequency tracking appears possible, but I, too, wonder how to handle the
waveshaping issue with such a long reset time.

  Ian

----- Original Message -----
From: "Haible Juergen" <Juergen.Haible at nbgm.siemens.de>
>
> Yes, charge pump. The CS-80 does this as well.
> I wonder how they fill the rather large gap of the saw reset time when
> a triangle is created.
>
> For those who are not familiar with that kind of VCO:
> Normally the scale error that is caused by the reset time of the saw wave
> must be compensated in the expo converter, and there ar a lot of
> stategies to keep that time small. The Chroma and CS-80 VCOs
> don't go for an ultra fast reset time, but the VCO concept includes a
> perfect compensation. At least that's who I understand it.
> I've seen a discrete design of this from R.A.Pease, and I think National
> still have such a chip as well.
>
> I wonder if ARP's HFT compensation in the Odyssey is a predecessor
> of this as well. There's a certain amount of charge used for compensation
> rather than a continuous current as well. (If memory serves. Was some time
> since I last looked at Odyssey schemos.)
>
> JH.
>
>