COG(NPO) Capacitors

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@tomchr

I've noticed your positive comments on these capacitors in audio circuits, and am curious about their suitability for filtering and coupling applications needing capacitances < 1.2nf or so. Can they sub in well for the ubiquitous Wima mkp red boxes and possibly better them? I'll be ordering caps for a project in several values to tune a circuit (the Pass Full Range EQ card), and will order some lower voltage COGs if you don't warn me off. And also some Wima's for comparison.

In that light, I'll also welcome make/brand and series (through hole) suggestions.

Thanks,

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NP0/C0G ceramic tend to outperform film capacitors - even polypropylene film capacitors. Do keep in mind that the physically large capacitors rated for higher voltage tend to work best, so choose a 0805, 1206, or larger with a rated voltage of at least 50 V. Go for 100 V if available. They're commonly available up to 100-220 nF for a reasonable cost. I have no reservations about using them in filters.

I haven't looked at the leaded parts in a while. Someone on diyAudio noted that the dipped leaded parts are often 0603 SMD caps with leads dipped in some sort of epoxy, so it could be worthwhile to go with SMD for that reason. Even if soldering SMD parts isn't your thing, I think you'll find the 1206 size quite easy to solder by hand.

Tom
 
Thanks Tom,

I've already put in sockets for the HF section of the filter, so I sounds like I should use several values of the Wimas to determine the best frequency of the dip they create, then remove those (sockets and caps), and use the SMD NPO/COG caps to bridge the through-hole solder pads. I would think putting them on the bottom might be best. I don't like to do rework at all, but this should be fairly easy. I hope the pitch of the holes isn't too much. I'll check before I order.

I jumped on Mark Johnson's AmyAlice filter project to learn SMD soldering last fall, and picked it up fairly easily, even with a crude mid-size chisel point iron. I hope a lot of us older folk will try it. Maybe I should suggest it as a workshop for BAF 2024.

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You're not likely to notice any difference in the frequency response of the filter. You will likely notice a difference in THD of the filter. At least Bruce Hofer of AP fame found the THD of those capacitors to be better than the THD of film caps.

I find a 1.6 mm chisel tip works well for most larger SMD soldering. If you do a lot of it, it can be well worth it to get a dissection microscope. I'd get an old-fashioned stereo microscope rather than the newer digital ones. The stereo microscopes offer depth perception which the cameras don't.

Tom
 
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