[sdiy] C0G/NP0 caps for VCOs

[rsdio at sounds.wa.com]

At 06:13 AM 10/14/2013, Andre Majorel wrote:
> I don't know what you folks have been using for VCOs lately but
> these look like a pretty good substitute for polystyrene
> capacitors :
What makes you think they'd particularly be good substitutes for  
polystyrene? I thought that the primary benefit of poly was the low  
self-absorption, so it seems like we'd need data on that to know.


On Oct 14, 2013, at 09:12, Ian Fritz wrote:
> Most of us have been using COG/NP0 for many years now.  I did  
> careful comparisons in high-performance VCOs and didn't see any  
> difference from PS.

What about for sample & hold circuits? I'm thinking that poly is  
really only critical for S&H, maybe less so for VCO. The last S&H  
that I designed has a PCB with multi-site pads for either poly (only  
available in through-hole) or C0G (1206), but I've only ever  
populated with the poly. The layout is nice, because the through-hole  
are as close as they can be anyway, but there's still room for the  
SMD pads in between. Only thing missing is that I haven't fully  
populated a board with the C0G to test performance. The S&H certainly  
works with C0G, but I have a 125 kHz update rate. I don't know how  
well it would work with the much slower update rate of like 100 Hz  
that you find on a hybrid synth with digital-controlled CV.

Brian Willoughby
Sound Consulting