[sdiy] expo accuracy? or integrator accuracy?, or both?

harrybissell harrybissell at prodigy.net
Sun Feb 9 23:24:48 CET 2003


OK good point.

for most of us... temperature stability is a minor issue. We need it... but in
reality
our ambient temperature is going to be fairly constant.

Not so the gigging musician. I still remember seeing Tangerine Dream at an
outdoor show and freezing my @ss off.  On stage the temperature must have been
higher (lights) but also very variable (cold wind).

Another issue is the range we wish to cover... often a synth will only be asked to
do
five octaves, not twenty...

There is good reason to want the most stable designs we can get... but also the
cirteria
for an 'acceptable' design could vary widely.

If it don't hear it as out of tune... it isn't  ;^P

H^) harry

Scott Gravenhorst wrote:

> DOH!  long thread...  And I'm in a linear world, so I don't think much about
> temperature effects.  If there are any temperature effects present in these
> non-expo circuits, they are smaller than I'm able to perceive.
>
> =?iso-8859-1?Q?Ren=E9?= Schmitz <uzs159 at uni-bonn.de> wrote:
> >Hi Scott,
> >
> >>Wow.  Well, if I follow the thread correctly, René, you've done this! (and I
> >>built [and use] a copy of the circuit).  You put together a very simple VCO
> >>using a 4069 gate for an integrator.  For what it's worth in this discussion,
> >>I got 9 octaves of linear operation out of such a "poor integrator".  It seems
> >>that even a poor integrator is sufficiently accurate for musical use.  For me,
> >>it casts doubt on whether the other much smaller influences are worth
> >>investigating at all.
> >
> >Well, that is true of course. And I know that the CMOS integrator can perform
> >over more octaves than that. (I have tried variations of that circuit too.)
> >The question here is not that of sweep range but of possible thermal effects.
> >I'd say by learning how the integrator performs at a lower loop gain one can
> >make a projection whether thermal (or other) dependancies of loop gain will
> >have an influence on oscillator behaviour or not.
> >
> >Cheers,
> > René
> >
> >
> >--
> >uzs159 at uni-bonn.de
> >http://www.uni-bonn.de/~uzs159
> >
> >
> >
> >
>
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