[sdiy] Linear detuning !

[karl dalen]

Hi simon
--- simon.oo.o at xs4all.nl skrev:

> Hi Karl,
> 
> karl dalen zei:
> > Here we go.
> >
> > Now, if  we add a tiny DC voltage to Iref
> > summing point we offset the VCO what if we
> > use the Expo CV voltage as the offset voltage?
> >
> > Constant multiplication of a varying linear voltage! Ugh!
> 
> Linear detuning means that the frequency is increased by a constant
> amount, for example, instead of 100 Hz or 5000 Hz you want 100.1 or 5000.1
> Hz.

Yes i know, i was just one of my "fun" ideas!  

Lets expand the wicked idea, we have two inputs to 
the NPN expo, B1 and B2, apply positive voltage V1
to B2 and frequency increases apply V1 voltage
to B1 and frequncy decreases. If we match the input 
resistors R1,R2 but let one of the divider resistors
become a pot, we can under compensate the expo.

As the V1 increases on B2 the voltage on B1 also increases
wich counteract the V1 voltage on B2 but if we make this "same"
voltage a fraction of V1 on B1 , a varying constant of the beat
over octaves then beat would stay constant!
(or close to).

However impedance on B1 might be wicked but not as a
sensitive matter as on B2.

The idea are, create a "scale voltage that equals the beat you want!
Ie, 1.000V scale on B2, and 0,002V scale on B1 automatically 
logs to constant beat over octaves if trimmed carefully!

Perhaps to difficult to tune!

Reg
KD