[sdiy] Query about best cap type for '2164 stability network

Phillip Gallo philgallo at gmail.com
Sun May 6 20:41:21 CEST 2018


If you want to have fun eliminate the '2164 lead-lag input compensation.
You'll find your '2164 performs quite differently.  I've wondered how many
have been thrown away do to broken or missing phase compensation.

The old Signetics AN142 has a short discussion of implementing a phase
lead-lag network for their NE5534 to deal with;

 "... impulse-related parameters such as damping and phase margin .." which
"... are controlled by choosing the appropriate circuit constants."

Worth a look.

regards,
p


On Sun, May 6, 2018 at 12:17 PM <rsdio at audiobanshee.com> wrote:

> Don’t underestimate the effects of microphony. I once had a non-audio
> circuit with capacitors where tapping on the case would cause spikes in the
> control signals because I just picked the cheapest caps. These were in the
> 560 pF range, but I was actually trying various values within an order of
> magnitude.
>
> So, you have to ask whether a non C0G/NP0 cap would alter the gain in the
> VCA and thus affect the audio, even if only slightly.
>
> Brian
>
>
> On May 6, 2018, at 10:16 AM, Guy McCusker <guy.mccusker at gmail.com> wrote:
> > You've given several reasons that C0Gs are good in general, and that's
> > why I tend to go for C0G for small value caps if I don't have a good
> > reason not to. But in the spirit of trying to learn about this stuff
> > properly, I wondered if there are any reasons particular to the 2164
> > application that would call for C0G over something else.
> >
> > It doesn't seem to me that the capacitance change with voltage or
> > temperature are essential in this application. The high frequency
> > performance may be. Is it?
> >
> > I realise that from an actual building standpoint this is a somewhat
> > academic question - we can just use C0G and stop worrying - but I like
> > worrying / learning.
> >
> > On Sat, May 5, 2018 at 9:41 AM, Richie Burnett <
> rburnett at richieburnett.co.uk> wrote:
> >> Low capacitance change with voltage and with temperature, low
> microphony, low loss at high frequency. C0G is the best you can get in
> small C values, in every respect except maybe size and cost. So no reason
> not to use it here for DIY unless you're counting every last penny or need
> to fit hundreds of them into a small space. But just for small cap sizes
> like hundreds of pF.
> >>
> >> -Richie,
> >>
> >> ---- Guy McCusker wrote ----
> >> What is the advantage of C0G in this application? Voltage derating and
> >> temperature coefficient don't seem critical. Could an X7R cap do bad /
> >> not as good things here?
> >>
> >> David is right that most of the 560pf ceramics at the usual
> >> distributors are C0G, but some are not, X7R being the next most
> >> popular. Tayda have some Z5U it seems.
> >>
> >> On 2018-05-04 10:32, Tom Wiltshire wrote:
> >>> What type of capacitor would be most suitable for the 500R/560pF
> >>> stability network on the input of the 2164 VCA? (In practice I mostly
> >>> use 560R/470pF - easier values to get).
> >>>
> >>> It's not directly in the audio path, so film caps seems like overkill.
> >>> Instead it's to take interference to ground, so it feels to me like
> >>> ceramic is appropriate.
> >>> Is that right, or would I be better off with something else? I realise
> >>> any improvement is unlikely to be audible, but I'm looking for
> >>> guidance on "best practice".
>
>
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