Xpander VCF

[Hairy Harry]

Hi Marjan...

in some modes, one stage is bypassed. That stage will be unstable
without ANY cap at all, so it is disabled by using a cap that is way too 
small (that pole tuned all the way up...)

Cap values also depend on what you like for cutoff frequencies.
Probably a wide range of caps work well, but match them to each other
is more important.


>From: ">>>marjan<<<" <urekar.m at EUnet.yu>
>To: Synth-DIY list <synth-diy at node12b53.a2000.nl>
>Subject: Xpander VCF
>Date: Wed, 25 Oct 2000 14:05:08 +0200
>
>Hi all,
>
>I was looking at OB Xpander's VCF on Grant's page, and while I
>understood
>theory of different filter modes, I can't figure out cap values used.
>In most of the quad OTA filters (CEM,SSM,13700) caps used are all the
>same value and in range 100p-1n (integration cap that is), and Xpander
>has 33n caps for first 3 stages (first stage can be switched "off" with
>100p cap needed for some modes) which seems too high, and fourth stage
>has 100 times smaller 330p cap. Why's that? And why so large caps?
>
>Cheers,
>
>
>marjan

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