Tim,

Thanks very much for the detailed explanation, as well as the time
you've taken on the whole thing.

Regards,
Kevin

--- In Doepfer_a100@y..., "stinchcombe_t" <tstinchcombe@q...> wrote:
> > But did he say (or is it possible) to lower the shift range, or
is it
> > more trouble than it's worth
>
> Having spent some more time studying the circuit over the weekend I
> now have a reasonable idea of the way it all works, and I suspect
the
> answer to your question is probably the latter - more trouble than
> it's worth. Adjusting the oscillator to run at lower frequencies
seems
> feasible, but it brings a few other problems with it: there is a
> considerable DC offset on the signal coming out of the oscillator,
and
> it depends on the control voltage (i.e. frequency) of the osc - at
> it's lowest freq its about +2V, at the high freq end its about -2V.
> This DC is blocked from the 1496 chips doing the main
multiplications
> by some capacitors - removing these to allow low frequencies through
> would also allow the DC through, and this is likely to upset the
whole
> 1496 set-up (which is pretty hard to figure out even *with* a 1496
> datasheet..). Also the amplitude of the osc output appears to
decrease
> as frequency decreases, therefore there is likely to be a point
where
> it just stops oscillating reliably. Which is not to say that it is
> impossible to lower the lowest shift frequency, just that it would
be
> non-trivial!
>
> Tim
>
> [The views expressed above are entirely those of the writer and do
not
> represent the views, policy or understanding of any other person or
> official body.]