[sdiy] Electronotes, op-amp substitution, thru-zero oscillator...

[Grant Richter]

>
> If I understand you application correctly:
> While they might all "sound DXish", you will in effect be modulating
> with a half- och fullwave rectified modulator, at least for small
> modulation indexes. That makes alot of the classic FM sounds
> impossible. Yes, you get sidebands, but much more harsch sounding.
> Sorry, I don't know the maths behind this. But I've noticed you can
> never make it sound as smooth and controlled with rectified modulator
> waves as with the others.
>

I understand your point.

But the design of the linear FM inputs on classic VCOs prevents them  
from reaching the zero point.
So they are not rectifying.

That is if you have the 1.5M to 15 volts and a 560K for linear FM.  
The linear current doesn't shut off completely.
According to Bernie Hutchins.

They are constrained to keeping the modulation index below reversing  
the phase vector.

What I don't understand is how allowing reversing of the phase vector  
affects the audio tone.
And if it is significant enough to be worth the cost of a $4.00 MAX365.

Another way to do it is in the wavetable itself. By adding a  
modulation vector to the phase vector with rollover.
Since I am thinking of an n dimensional wave terrain, that could be  
just another wavetable input.