[sdiy] 2164 tempco in VCF applications

David G Dixon dixon at mail.ubc.ca
Tue Nov 6 21:22:27 CET 2018

Hi Rutger,
I tempco my 2164s in filters when only using two or three VCAs in the core
(or, for example, in an SVF where I use two in the core, one for VCQ, and
the fourth for tempco).  However, in a Roland-esque four-stage filter, I
generally don't do tempco.  You would essentially require two independent CV
summers, two tempcos, and then split the core between two 2164s (two on
each) so that each one had an unused spare.  It's probably not worth all the
trouble, since filter cutoff doesn't require tempco, and there are more
convenient ways to get sine waves.


From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Rutger
Sent: Tuesday, November 06, 2018 7:29 AM
To: SDIY List
Subject: [sdiy] 2164 tempco in VCF applications

Hi list, 

I've been impressed with the performance of recent VCO designs (yes, you
David!) using 2164 for temperature compensation. I've been wondering if
people have attempted similar things with respect to VCF applications? When
using integrators in a VCF based on the 2164 you already have an exponential
control law of the inputs, so wouldn't need a full exponential current
source as in a VCO. Can you still apply the same principle for making a VCF
temperature stable? Do you need that degree of stability in a VCF (yes,
different opinions are welcome)? And what would you do if you already used
up all 4 sections of a 2164 in the core of the VCF, meaning you don't have
another 2164 available in the same (isothermic) package?



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