a few simple questions

[Martin Czech]

>    Hmm, I'd say that CV's range more on the 0 to 10V scale.  Of course 
> there really is _no_ set standard.  Actually it's more practical to have 
> CV's that range the same as your audio.  

And by the way, most opamps (all types that I use) can't go from rail
to rail.  I.e. +-15V is not possible with +-15V supply, you can get at
most ~ 13V.  The 10V thing seems to be a tradition from old analog
computing.  And another argument: a vco with 1V/octave (another
standard, I think from Moog and ARP) needs 10V for a sweep of 1:1024 and
this is about the width you need for sweeping across the entire audio
band.
 
>I.E. if you have 10Vpp audio 
> signals (we're talking modulars here) then to really have fun, your CV's 
> should be +-5V.  This way you can plug in audio and CVs anywhere with no 
> converters needed.

Well, the range of audio should be the same than that for modulation, I
aggree.  There's really no difference between both types of signal.  A
slow lfo wave can turn into an audio signal, if it goes above ~20Hz.
(As the pioneers of e.m. found: the transition between rythm (slow lfo
square ~1Hz) motor boat (faster) and pitched sound (>20Hz) :->).

But CVs usually don't go and should not go from -5 to +5V. Most VCA
designs need 0-10V. What I want to say is that CVs should have at least
a max. peak-to-peak value of 10V, but some offset can be added
before/after attenuation.

Example:

VCF set somewhere in the middle and -3 to 2 V CV (LFO) will sweep from
the middle to low and then rise up to the highest frequencys.  This can
be done using a -2.5V to 2.5V LFO output and an offset of -0.5V.  If
the LFO output is automatically controlled by an adsr/vca combination
the insertion point of the offset voltage matters. Before the vca, all
modulation will disapear if the vca is closed, after vca the offset
will remain of course.  Both patches can be usefull.

m.c.

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