[sdiy] Silvered mica caps in VCO core integrators

David G Dixon dixon at mail.ubc.ca
Sun Apr 17 08:52:27 CEST 2016

I'm inclined to agree.  As far as Ian Fritz's "modern standard" is
concerned, I seriously doubt that you could find any synth modules for sale
in any format (with the possible exception of his own designs) that conform
to that standard -- not even close.  Most commercial synth VCOs track
decently over only 5 or 6 octaves.  My "Dixie" design (as sold by
Intellijel) tracks 10 to 12 octaves within 0.1% error when properly
calibrated, and it doesn't even use an exponential converter -- it uses a
2164 VCA as expo converter, with another 2164 VCA for temperature
compensation.  There is a two-transistor expo converter -- as a
high-frequency correction circuit, injecting anti-error current into the CV
summer.  It's probably the best tracking VCO in eurorack format, and I'd put
it up against anything in 5U.  I doubt that will be affected significantly
if I use a mica cap in the core.

> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl] 
> On Behalf Of Tony Clark
> Sent: Saturday, April 16, 2016 11:29 PM
> To: Sdiy
> Subject: Re: [sdiy] Silvered mica caps in VCO core integrators
> tl;dr
> I wouldn't hesitate AT ALL to use Mica's for VCO's.  I used 
> Mica caps for the VCO circuits I designed 17 years ago and 
> they still work just fine.
> Unless you are Mr. Chowning and have some new fangled retro 
> analog bent, I wouldn't be too concerned about your VCO 
> meeting some silly "modern standard" (and is it IEEE?).  If 
> it works for you, it works.
> If it doesn't, pick a different part.  It's not hard to swap 
> out a silly cap.
> Tony
> -- 
> Tony Clark
> Great Lakes Modular
> www.greatlakesmodular.com
> Design, Engineering, and Manufacturing Services
> --
> On Facebook:  https://www.facebook.com/greatlakesmodular
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