2 cascaded resistive dividers with ldrs

[jhaible]

> I might be completely wrong, but when I have seen a rheostat, there was
> always a lower leg resistor, e.g. the 1k resistor from the differential
> input transistor base to ground (fvrom my head).  So this is also a
> voltage divider with a constant leg, like in my proposal.  I think that
this
> "rheostat" configuration is not very sensitive when the resistance is
> high, but on the other end. This seems to be the reason for the need
> for inverse log pots.

In a certain circuit of this kind, there is a capacitor in series with the
rheostat,
so changing the feedback gain will also change the corner frequency of the
HPF
in the feedback loop.

JH.