[sdiy] SSI2144 filter caps

[Mattias Rickardsson]

X7R and similar deramics can be microphonic - mostly problematic in a
differential application, but test & verify it also in others. They
also have a strong voltage dependency, which is not only a problem if
there is a DC offset, but it immediately distorts all signals that are
non-zero. Which useful signals tend to be. ;-)

Rumor is that C0G / NP0 (those are both zeros!) caps tend to be free
from these problems and I trust them a lot... but still, worth a test
or two. We recently experienced microphony on a prototype with caps
that were allegedly C0G.

/mr


On 12 September 2017 at 13:20, Steve <sleepy_dog at gmx.de> wrote:
>
> What about ceramic caps being microphonic, and the effect of changing capacity when there's a DC offset, are C0G / NP0 free from those effects?
>
> - Steve
>
>
>
> Guy McCusker wrote:
>
>> Didn't Ian Fritz teach us that NP0 is just as good as polystyrene?
>> (Provided you can obtain a cap of the correct value of course.)
>
>> Right now all I can find is this message in the archives:
>> https://synth-diy.org/pipermail/synth-diy/2011-April/031915.html
>
>> If Ian has more to say I would love to hear it...
>
> On Tue, Sep 12, 2017 at 8:28 AM, Roman Sowa <modular at go2.pl> wrote:
>> I used NPO 0603 ceramics, and it sounds great.
>> http://www.synthdiy.eu/files/2144.jpg[http://www.synthdiy.eu/files/2144.jpg]
>>
>> There are also 3 audio examples in my Soundcloud if anybody is interested.
>>
>> Roman
>>
>> W dniu 2017-09-12 o 00:19, Tim Ressel pisze:
>>>
>>> Yo,
>>>
>>> So I am working on SSI2144 filter designs and I can't help but notice
>>> the polystyrene caps are biggish. Can I get away with poly film box caps?
>>>
>>> --tr
>>>
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