[sdiy] VCF caps in modern synths

[cheater cheater]

They don't even mention the voltage coefficient. So how do you know
their capacitance isn't voltage dependent?

On Sun, Mar 28, 2021 at 5:52 PM Justin Herrmann <ebn303afxcut at email.com> wrote:
>
> Hi All,
>
> NP0/C0G has almost no voltage coefficient (it's the best): https://www.avx.com/products/ceramic-capacitors/surface-mount/c0g-np0/
>
> Justin Herrmann
> On 3/28/21, 10:10 AM cheater cheater <cheater00social at gmail.com> wrote:
>>
>> On Sun, Mar 28, 2021 at 4:47 PM Mattias Rickardsson <mr at analogue.org> wrote:
>> > I've never heard of aspers before, but it seems to refer to modulation in the lower audio frequencies (20-300 Hz) rather than harmonic distortion: https://community.sw.siemens.com/s/article/sound-modulation-metrics-fluctuation-strength-and-roughness
>>
>> Your article talks about roughness in a very specific situation. See
>> the parallel thread for a paper by Hoeldrich which measures roughness
>> in full-band.
>>
>> >> alternatively go to something like mV range and have a much more linear, tiny, capacitor - but at the cost of EMI adding a bunch of noise. Your choice. Fully-balanced synths anyone?
>> >
>> > since the self-modulation goes in the other direction for negative voltages, a straight-up balanced design wouldn't help much.
>>
>> The capacitance is reduced (i.e. affected in "the same direction") for
>> both positive and negative voltages. The suggestion here was to have
>> very low voltages. The balancing would be used to remove EMI noise
>> from external interference. Not to cancel out the capacitance
>> reduction.
>>
>> > Some research into the nonlinearities would be essential. Or why not go for C0G instead. :-)
>>
>> C0G are specifically the ones that have the extreme variation in
>> capacitance based on applied voltage. They're the ones mentioned in
>> the article. So going for C0G is the worst thing you can do. I'm not
>> sure but I guess Colin's test was on a synth with NP0 capacitors or
>> ones that are built very similarly. Most ceramic capacitors with high
>> voltage ratings in a small package will be multi-layer, built just
>> like C0GNP0.
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace at synth-diy.org