[sdiy] low cost ic oscilator question

[patchell]

    Hmmm...that is a good question.  The only instrument I have ever seen a
seperate oscilator per key (an organ, I can't remember the make) used an LC
type oscilator.  And I suspect that the reason is for stability.  Also
probably because this was easier to do with tubes also....  Using a 40106 in
an RC type oscilator, the frequency is going to depend not only the RC
elements, but also the thresholds of the 40106, which are going to drift all
over the place (well, may not quite that bad) with temperature.  A linear LC
oscilator will depend, for the most part, only on the L and C , and to a
lesser degree the gain of the amplifier.  But, you can build a Colpits or
Hartley oscialtor with just a single transistor.  This was how the Wurlitzer
Combo organ I used to have was done...hmm...wonder if I still have the
oscilator boards from that?....Still, if nothing else, build up a set of
oscilators using the 40106 and see how stable they are.  Should be a simple
enough experiment.

Peter Blackett wrote:

> Hi,
> I'm thinking of modifying an old keyboard of mine  that presently uses a
> top octave generator ic , into using 12 seperate oscilators .
> I was wonderting if anyone had any recommendations as to what Ic I
> should use to generate the frequencies ?
> I was thinking of using an RC oscilator circuit rather than using tuned
> inductors.
> I know that I will loose the ability to shift the whole set of
> frequencies up and down with one tuning control , but I want to
> experiment with being able to change the frequency of each of the 12
> notes of the scale .
> also If the frequncy stability of the oscilators is good enough I might
> try having seperate osciltors for each note of the keyboard.
> I had thought about using the 40106 ic , but I don't know if this would
> be a good idea .
> I know Korg produced a Symphonic ensemble PE1000 keyboard many years
> ago, but I can't remember  which ic they used for the seperate
> oscilators .
> any advice is appreciated
> regards Peter

--
 -Jim
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