The drop to zero is not the important thing (except for LFO applications
where the modulation can stop and continue again when the linear control is
turned up again). But the linear frequency bias/offset is important because
the linear FM is different when the bias/offset gets lower. Usually VCOs
even with a linear FM input have no linear frequency control. The internal
circuit of the VCO multiplies the shares of the linear and exponential
section to define the VCO frequency. Without the manual linear frequency
control the linear share (without linear FM) has a fixed value which is
typically near at it's maximum. A linear FM with e.g. 1 Vpp applied to the
circuit is totally different compared to a situation with e.g. half the
linear frequency bias/offset. With the LF control you are able to control
the linear FM much better than without this feature. The standard VCO
situation of the A-111-2 is with LF control fully CW (i.e. the linear share
near to maximum).

Best wishes
Dieter Doepfer

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto: Doepfer_a100@yahoogroups.com ]
> Gesendet: Donnerstag, 8. September 2016 22:00
> An: Doepfer_a100@yahoogroups.com
> Betreff: Re: AW: 1 A-111-2 question
>
>
>
>
>
> Thanks Dieter,
>
>
> Can I ask what the application of a manual drop to zero is
>
>
> Neil
>
> Sent from my iPhone
>
> On 8 Sep 2016, at 18:56, yahoo@... 1
> < Doepfer_a100@yahoogroups.com > wrote:
>
>
>
> The A-111-2 has no thru-zero feature but only a manual control and a CV
> input for linear frequency adjustment/modulation. With all controls at
> minimum the oscillation nearly stops (typ. 1Hz in VCO mode). But we are
> working on a thru zero version of the A-111-2 (probably named
> A-111-4). But
> it's too early to publish any details as the circuit is a bit more
> complicated. It's based on a suggestion by Doug Curtis in his documents we
> obtained while we were the European distributor for the Curtis
> chips in the
> the eighties. The circuit is similar to the CEM3340 based thru zero VCO by
> Juergen Haible but with a few more features (like zero point modulation).
>
> Best wishes
> Dieter Doepfer
>
> > Hi people,
> >
> > Does anyone know if the new VCO has thru zero capability It
> > looks like it from the LF control being able to go to 0 but there
> > isn't specify mention.
> >
> > Neil
>
>
>
>
>
>