[RE: [Re: UNFAIR LFO voltage?]]

[Harry Bissell]

Harry Bissell writes:
The crux of this matter may be more in what is more possible/desirable to
design, rather than how we use it. If you want bipolar modulation
(triangle/sine) you better decide up front. For me, any offsets in the LFO
can't be tolerated, as they throw the pitch off when the amount (depth) is
changed. Likewise the square wave better have a real good ground reference...
same reason. It is easier to design a circuit to add some offset to a signal
that has no offset... than it is to design a circuit to remove an unintended
offset. Let's face it, a "summing" amp beats the hell out of some "dc
restoration" circuit. AC coupled (yuck!) LFO's, anyone ????


jh <jhaible at primus-online.de> wrote:
>Does it really matter what a non electronic / synth instrument does
>or is capable of modulation wise?  Certainly, it is valuable to study
>this, but an LFO can have an output stage with _adjustable_ 
>amplitude, phase reversal, and offset to allow
>the "patcher" to create whatever effect is desired.  This kind of
>modulation source would allow for more _or_ less "natural" kinds
>of modulation.  But more to the point, I think it's good that it
>can be non-natural.  After all, if I want a guitar sound, well, I
>pick up a guitar...  Electronics lends itself so well to making things
>"adjustable".  That's one reason why it's fun, eh?  So add another knob.

I agree - and yet sometimes I don't. 
Sometimes I find myself asking how to *remove* another knob rather
than adding one. I used to think that as many knobs as possible 
is the one and only way - until I stood face to face with one of these
Jellinghaus (sp?) DX-7-Programmers one day.

Let me take up that example of the unipolar / bipolar LFO:

(1) The cheap solution:
"What - how could anybody want anything else than bipolar ?
You're the first one to ask such a strange thing"

(2) The cheap solution, vol. 2:
"If you want to have an optional level shift, buy our Voltage
Processor module, and mix in your desired offset voltage."

(3) The "I thought of everything" solution:
One knob for output level, one knob for DC offset, external
CV input for amplitude control, external CV input for DC
offset control, two more knobs for sensitivity of these CV
inputs, center Zero pots for increasing or decreasing
the parameter ...

(4) The "guitar amp" solution:
One knob for LFO output level. Pull-Pot switch to add
a carefully chosen DC offset to emulate a certain
fashionable effect derived from a natuaral instrument's
behaviour.

There may be more, but you get the point. My own
"roots" are surely in option (3), but I start to see the
advantages of option (4) more and more.

JH.


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