[sdiy] What is a quadrature oscillator good for?

[jhaible at debitel.net]

>    > From: "jhaible" <jhaible at debitel.net>
>    > Date: Tue, 16 Sep 2003 02:33:16 +0200
>    > 
>    > > Ooops, sorry, you mean leakage in the form of a resistance.
>    > >
>    > > Sure, that shows up as if the rotating object had a very slight
>    > > amount of spring to cause it to drift to certain position.
>    > 
>    > In your Leslie example, will the position stay fixed over
>    > 20 minutes (because you play 3 songs with the organ
>    > thru leslie in stop position) ?
> 
> 20 minutes?  Sure, but not with any accuracy.  I certainly don't have
> any breakthrough technology to hold capacitor voltages steady.
> But... at least it won't drift more than a quarter cycle.

Well, this was more a rhethorical question, because you came up with the
Leslie-Stop example. 

For ordinary LFO applications, a little drift does not hurt much, as
long as the LFO still runs thru its full cycle. No one will notice
a duty cylce of 30% (due to offset currents) on a LFO of several
minutes period time, unless he really has a stop watch in his hands.
But if you have a Quadrature Oscillator application like the 
volume and panning part of a Leslie, or an Infinite Phasing created
with a Frequency Shifter, you would notice such an error.

As a funny side note, Dynacord have the pan modulation part of
their CLS-222 AC-coupled, so they are "cheating". When you
start the (simulated) motor after some time, the first rotation
always sounds a bit unrealistic. (compared to the decentsimulation in normally 
does.)

JH.

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