[sdiy] VCF caps in modern synths

[ColinMuirDorward]

Here is a little update to this topic.
Some good people at GS have photographed the VCF section on two behri 2600
versions: orange/black and grey.
You can see that in orange, they used SMD ceramics, and on grey, yellow box
film.
Lucky for us, the orange version has empty through-hole footprints!
https://www.gearslutz.com/board/attachments/electronic-music-instruments-and-electronic-music-production/953304d1616358816-behringer-2600-a-2600vs2600.jpg

On Mon, Jan 18, 2021 at 11:49 AM ColinMuirDorward <colindorward at gmail.com>
wrote:

> Was there an audible difference between the two capacitor types with the
> same frequency/resonance
> setting on the filter?
>
> If this question was for me, then here is my answer: In my 4pole 3320 BPF,
> the polypropylenes sound slightly better. The obvious difference is that at
> lower frequency settings, they go into self-oscillation more readily than
> the ceramics. To my biased ear, the ceramics make some small distortion
> perhaps, or for some reason add a slight edge to the sound. I did do a
> blind test using a 2pole 2164 SVF and the difference there is more
> noticeable than in any other filter I've tested. Here, the polys are a
> clear win. I want to use words like "liquid, juicy, lush" for the polys vs
> "bite, edge, grit" for the ceramics. However those are too strong words to
> describe a very subtle difference. I am waiting to find the right modern
> mono synth that I can do a capacitor "upgrade" on and test if it's possible
> to perceive a change in the sound in a factory-made unit. I have an uno
> synth on the way (was on sale for $135cad?!), perhaps I'll be lucky enough
> to find space inside that tiny case for four WIMAs.
>
> I also would like to add a big thanks for all the conversation on this
> topic! Every time I say the word "capacitor" around here, I learn so much!
> Last time it was about bypass caps, and now this topic as well has been
> very good reading.
>
> Cheers,
> Colin
>
> On Sun, Jan 17, 2021 at 9:36 PM Tristan <tu at alphalink.com.au> wrote:
>
>> Was there an audible difference between the two capacitor types with the
>> same frequency/resonance
>> setting on the filter?
>>
>> /Tristan
>>
>> On Mon, Jan 18th, 2021 at 11:19 AM, Mike Bryant <
>> mbryant at futurehorizons.com> wrote:
>>
>> > Agreed lead inductance would be tiny.  I was thinking more of inductive
>> > coupling between the lead inductances if the capacitors are mounted
>> close
>> > together, or close to a high level signal.  This can easily happen in
>> the MHz
>> > range and adversely affect the audio performance.
>> >
>> > -----Original Message-----
>> > From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of
>> > Gordonjcp
>> > Sent: 18 January 2021 00:07
>> > To: synth-diy at synth-diy.org
>> > Subject: Re: [sdiy] VCF caps in modern synths
>> >
>> > On Fri, Jan 08, 2021 at 03:29:44PM +0000, Mike Bryant wrote:
>> > >
>> > > >Yesterday I did some very non-scientific testing of 3320 4pole BPF
>> built
>> > using C0G vs polypropylenes. The test may have been more about the
>> tolerances
>> > of the caps rather than the dielectric, since my polys are 2.5% vs the
>> C0Gs
>> > at 5%. I noticed that at lower frequencies, the polypropylene version
>> would
>> > go into oscillation before the C0G version. Any thoughts on this?
>> > >
>> > > Was this SMD or through hole ?   It’s possibly down to lead
>> inductance or
>> > series resistance being higher in the C0G.
>> > >
>> >
>> > Lead inductance would be tiny, negligible at audio.  If your VCF is
>> > oscillating in the low GHz range you might have issues.
>> >
>> > --
>> > Gordonjcp
>> >
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>>
>>
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>
>
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