[sdiy] VCO Linear Voltage

[jhaible at debitel.net]

Zitat von Jerry Gray-Eskue <jerryge at cableone.net>:

> 
> I see how it would be useful in a LFO for envelope control, but I still do
> not get why it would be better for audio FM patches.
> 
> If we setup a patch to vary the pitch at say 440hz by 20 cents using linear
> FM, one octave up at 880hz the variation is only 10 cents, two octaves up it
> is down to 5 cents. So how is this better than using the 1 Volt per Octave
> input for FM to vary the pitch at a fixed 20 cents for all frequencies?
> 
> Is it just a "Cool" effect that people like?

In VCOs that have both, linear and expo control, the two are normally
multiplied. So you get the same amount of detuning in cents across the keyboard
even using the linear FM for the LFO.

The benefit of linear FM lies in *deep* modulation patches: The average (DC
value) of a zero-centered LFO is still zero after the linear FM process, while
expo FM generates a non-zero average, i.e. detuning that increases with
modulation depth.

JH.


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