Further digging has answered this for me - close for DC FM (i.e. continuous source voltage), open for AC (i.e. audio).

It's all there if I look for it ;-)

Dave.

--- In Doepfer_a100@yahoogroups.com , "woof_dave" <David.Woof@...> wrote:
>
> Hi,
>
> I'm adding the extra connections, etc, to make the linear FM change to the A-110 VCO, and it isn't clear to me whether the "AC/DC Coupling" jumper should be open (as per the default), or closed when the linear FM addition is made.
>
> Anyone know which state it should be in
>
> Thanks,
>
> Dave.
>