[sdiy] Silvered mica caps in VCO core integrators

Ian Fritz ijfritz at comcast.net
Fri Apr 15 20:41:58 CEST 2016


What exactly do you mean by "no problems"?  Can you track reliably to 
within 0.05% over 15 octaves up to 30 kHz? That's the modern standard.

On 4/15/2016 10:46 AM, Vinicius Brazil wrote:
> Precision & Stability. In RF we need precision, that´s the reason to the
> use.
> I also had no problems in AF circuits.
>
> On Fri, Apr 15, 2016 at 1:29 PM, David G Dixon <dixon at mail.ubc.ca
> <mailto:dixon at mail.ubc.ca>> wrote:
>
>     That's what I wanted to know (but was afraid to ask).  Silvered mica
>     caps
>     are more or less insisted upon in RF circuits.  What becomes so bad
>     in AF
>     circuits?
>
>      > -----Original Message-----
>      > From: Synth-diy [mailto:synth-diy-bounces at dropmix.xs4all.nl
>     <mailto:synth-diy-bounces at dropmix.xs4all.nl>]
>      > On Behalf Of Simon Brouwer
>      > Sent: Friday, April 15, 2016 3:57 AM
>      > To: Ian Fritz; Sdiy
>      > Subject: Re: [sdiy] Silvered mica caps in VCO core integrators
>      >
>      > Hi,
>      >
>      > Why is soakage an issue in VCO's?
>      >
>      > My impression is that the time constant of the soakage effect
>      > is orders of magnitude longer than the period of audio range
>      > signals. If that is correct, soakage would not significantly
>      > affect the frequency stability of a VCO, or would it?
>      >
>      > Best regards
>      > Simon
>      >
>      > > On 15 April 2016 at 03:56 Ian Fritz <ijfritz at comcast.net
>     <mailto:ijfritz at comcast.net>> wrote:
>      > >
>      > >
>      > > Mica caps have too much dielectric soakage for serious use in VCOs.
>      > > (See the famous Bob Pease writeups.)
>      > >
>      > > My super S/H project was started to compare soakage and
>      > leakage in C0G
>      > > ceramics vs plastics.  I found that C0G and polystyrene had nearly
>      > > equivalent behavior.  Other plastics, including PPE, were inferior.
>      > >
>      > > I'll say it again: C0G is the way to go for high-performance synth
>      > > circuits, especially given their small size and reasonable cost.
>      > >
>      > > Ian
>      > >
>      > >
>      > > On 4/14/2016 4:33 PM, Pete Hartman wrote:
>      > > > Film caps generally seem to be preferred, but I can't say
>      > I've heard
>      > > > any strong arguments for one type of film cap over
>      > another for that purpose.
>      > > >
>      > > > Thanks
>      > > >
>      > > > Pete
>      > > >
>      > > > On Thu, Apr 14, 2016 at 4:25 PM, David G Dixon
>     <dixon at mail.ubc.ca <mailto:dixon at mail.ubc.ca>
>      > > > <mailto:dixon at mail.ubc.ca <mailto:dixon at mail.ubc.ca>>> wrote:
>      > > >
>      > > >     Yves suggests either polystyrene or silvered mica.  I
>      > guess they're
>      > > >     interchangeable...?  I think silvered mica are easier
>      > to use (and to
>      > > >     get).
>      > > >
>      > > >      > -----Original Message-----
>      > > >      > From: Quincas Moreira [mailto:quincas at gmail.com
>     <mailto:quincas at gmail.com>
>      > > >     <mailto:quincas at gmail.com <mailto:quincas at gmail.com>>]
>      > > >      > Sent: Thursday, April 14, 2016 2:15 PM
>      > > >      > To: David G Dixon
>      > > >      > Cc: Sdiy
>      > > >      > Subject: Re: [sdiy] Silvered mica caps in VCO core
>      > integrators
>      > > >      >
>      > > >      > I use polystyrene (as per Ray Wilson's
>      > instructions)  but I'm
>      > > >      > willing to bet Mica will be perfect as well.  In
>      > fact I think
>      > > >      > Yves Usson uses Mica for that in his VCO:
>      > > >      > http://yusynth.net/Modular/EN/VCO/index.html
>      > > >      >
>      > > >      > On Thu, Apr 14, 2016 at 3:53 PM, David G Dixon
>      > > >      > <dixon at mail.ubc.ca <mailto:dixon at mail.ubc.ca>
>     <mailto:dixon at mail.ubc.ca <mailto:dixon at mail.ubc.ca>>> wrote:
>      > > >      > > Hey team, what do we think about silvered mica
>      > caps in VCO
>      > > >      > core integrators?
>      > > >      > > I've used them in filters, and they work great.
>      > Any hidden
>      > > >      > dangers I
>      > > >      > > should be aware of?
>      > > >      > >
>      > > >      > > _______________________________________________
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>     <mailto:Synth-diy at synth-diy.org>>
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>      > > >      >
>      > > >      >
>      > > >      >
>      > > >      > --
>      > > >      > Quincas Moreira
>      > > >      > Test Pilot at VBrazil Modular
>      > > >
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-- 
ijfritz.byethost4.com


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