[sdiy] Help with Timing Capacitor types.

[Mike Beauchamp]

Thanks for the reply Paul, I figured there was no harm in going
through all the datasheets anyways.

For the sake of being the naive noob (and please bear with me) the
xircon polystyrene caps at Mouser list a temperature coefficient of
+/- 150ppm/C, which is greater than the 100ppm/C of the Polyphenylene
Film capacitors I mentioned. I'm guessing there are other reasons why
Polystyrene caps are the *only* good VCO cap, since it can't just be
temperature stability.

Also Mouser doesn't carry .047uF polystyrene caps, and maybe that's
why the timing cap in Thomas Henry's XR-2206 VCO just calls for Mylar.
The reason I'm researching alternatives is that I'm trying to put out
a few more VCO designs based off the xr-2206, including a
really-really stripped down simple vco/noise maker for beginner
projects and then hopefully a more versatile/accurate/stable version.

Oh by the way, thanks for the entertaining read regarding the
Concertmate development Paul. A local band had one on stage a few
nights ago, so I was reading about the thing earlier tonight and got
to the development write-up via wikipedia and then recognized your
name.

Mike

On 3/4/07, Paul Schreiber <synth1 at airmail.net> wrote:
> The *only* good VCO cap is polystyrene. Mouser (www.mouser.com) sells them, not
> an issue. I've used 1000s of them in VCOs and in VCFs.
>
> If you are not in the US, maybe Mouser is not a good "international shipper"
> (shrug). But I live about 30mi away, not problem for me :)
>
> Paul S.
>
>


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Mike Beauchamp
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