I'm building a simple DAC based on the PCM2912A, and it's datasheet recommends placing a 100u capacitor, and when I checked the respective evaluation board I saw that they used electrolytic capacitors.
I'm wondering if boosting the capacitance of said cap up to 330u or more will benefit the sound quality? Increasing the capacitance should reduce the -3dB point of the HP filter that is formed with said caps.
I also wonder if it's advantageous (or not) to add a smaller polymer cap in parallel with the big one. Since these have better responses at higher frequencies that electrolytic ones.
Thanks in advance!
I'm wondering if boosting the capacitance of said cap up to 330u or more will benefit the sound quality? Increasing the capacitance should reduce the -3dB point of the HP filter that is formed with said caps.
I also wonder if it's advantageous (or not) to add a smaller polymer cap in parallel with the big one. Since these have better responses at higher frequencies that electrolytic ones.
Thanks in advance!
I heartily agree that 100uF is woefully low to be driving 16- or even 32ohm headphones with. Even 330uF is too low, aim for at least 1000uF. I normally use 2200uF or 3300uF for 56ohm cans.
Adding a polymer in parallel won't help, might even hinder as polymers tend to have highish leakage currents. Sure they have nice low ESRs but the ESR of a normal 'lytic is perfectly fine for this application.
Adding a polymer in parallel won't help, might even hinder as polymers tend to have highish leakage currents. Sure they have nice low ESRs but the ESR of a normal 'lytic is perfectly fine for this application.
I see. I though that the caps would be reverse polarized on the "negative" parts of the sine wave.
The idea is to add a polymer/polyester cap in parallel with a electrolytic one, since those have better high Hz response. Is it a good idea? Well that's what I want to know ahah
Strange but true? I have found two electro caps in "super e" sound a little better than one of half the value (depending on the cap), and a bypass with a small film cap (MKP1837 10nF for example) allows greater fine detail retrieval than an electro with no parallel cap. The choice of caps matter in such cases. These caps change sound over time too, most notable in the first few hours of use. Not all electros sound the same as AC coupling caps either - Panasonic's "made for audio" AM series don't sound good as ac coupling for example but Elna Silmic II do. Best small electros I've had were Rubycon Blackgate NX hi-q.
BTW these are not my ideas - vast numbers of people have said the same over the years and I'm just echoing others.
So, to me, it's definitely worth trying these things yourself - if you can't hear the difference then, in this case, it really doesn't matter, but i thought i should share this, because, if nothing else, it balances the DiyAudio replies with ones you'd get on other forums.
There's been a ton of articles about how caps sound and picking the best ones for a given job too. It's actually a huge topic, so it's weird to see people here say the exact opposite - any common big electro will do. I think any common electro over 470uF will do, and in your application, this might be the best advice as well. Bear in mind what frequencies the headphones/speakers can reproduce, and that some people want to filter subsonics. If you're not sure, a Panasonic FC 1000uF is a default choice.
BTW these are not my ideas - vast numbers of people have said the same over the years and I'm just echoing others.
So, to me, it's definitely worth trying these things yourself - if you can't hear the difference then, in this case, it really doesn't matter, but i thought i should share this, because, if nothing else, it balances the DiyAudio replies with ones you'd get on other forums.
There's been a ton of articles about how caps sound and picking the best ones for a given job too. It's actually a huge topic, so it's weird to see people here say the exact opposite - any common big electro will do. I think any common electro over 470uF will do, and in your application, this might be the best advice as well. Bear in mind what frequencies the headphones/speakers can reproduce, and that some people want to filter subsonics. If you're not sure, a Panasonic FC 1000uF is a default choice.
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Some people say if an electrolytic is sized big enough so that the AC voltage across it is less than 60mV or so at the lowest frequency of use then it shouldn't distort. That may have been based on some published measurements by Doug Self.
The reason they take the position about caps that they do is because a lot of people also rave about things like wooden cable lifters. The question becomes, how do folks who don't hear a difference in caps differentiate valid claims from ones that have to be largely psychological?
They would like people making claims about sound quality to figure out some measurement that correlates with what they hear. Or at least to do some high quality double blind studies to show there is a real effect. Problem there is that doing the research is hard and expensive. Nobody wants to foot the bill for doing it. So we are at a sticking point. Not hard to understand. Just hard to fix.
The reason they take the position about caps that they do is because a lot of people also rave about things like wooden cable lifters. The question becomes, how do folks who don't hear a difference in caps differentiate valid claims from ones that have to be largely psychological?
They would like people making claims about sound quality to figure out some measurement that correlates with what they hear. Or at least to do some high quality double blind studies to show there is a real effect. Problem there is that doing the research is hard and expensive. Nobody wants to foot the bill for doing it. So we are at a sticking point. Not hard to understand. Just hard to fix.
I think those things (measurements, DBTs) aren't at all likely to happen because the people comparing caps aren't in general technical types. What could I think happen (but doesn't seem very likely to me) is that instead of waxing lyrical about their fave caps they gave some falsifiable descriptions of how they sound on which recordings with sufficient details about the hardware involved that the listening setup could be replicated.
Thank you for your reply!
I can see that this is actually a somewhat divisive topic, and not as straightforward!
This is my first ""hi-fi"" (emphasis on the quotes) so i think I'll keep it simple! I'll just place some good ol'electrolytic caps! Although I might go a bit above 1000uF...if I have the space and money for it of course
An output coupling capacitor (like all coupling capacitors) has to:
1. have low enough leakage that it blocks DC - in most cases an electrolytic will do, but the bigger the cap the more the leakage (in general)
2. have high enough capacitance that it does not attenuate wanted low frequencies
3. have high enough capacitance that even at low frequencies it has little signal voltage across it, and therefore is incapable of adding significant distortion
4. have low enough inductance that it maintains a sufficiently low impedance at high audio frequencies - almost any electrolytic will do this, but very big ones may not and bypassed one may not because the bypass capacitance and the electrolytic inductance have opposite sign and so oppose each other.
If you can hear a coupling cap then you probably have chosen the wrong value. If you can hear the effect of a 'bypass cap' then this almost certainly means that the main cap has too much inductance so adding a 'bypass' makes things worse; instead, use a smaller main cap. Be aware that people expecting an improvement are likely to hear any change as an improvement even when it is actually a minor degradation.
1. have low enough leakage that it blocks DC - in most cases an electrolytic will do, but the bigger the cap the more the leakage (in general)
2. have high enough capacitance that it does not attenuate wanted low frequencies
3. have high enough capacitance that even at low frequencies it has little signal voltage across it, and therefore is incapable of adding significant distortion
4. have low enough inductance that it maintains a sufficiently low impedance at high audio frequencies - almost any electrolytic will do this, but very big ones may not and bypassed one may not because the bypass capacitance and the electrolytic inductance have opposite sign and so oppose each other.
If you can hear a coupling cap then you probably have chosen the wrong value. If you can hear the effect of a 'bypass cap' then this almost certainly means that the main cap has too much inductance so adding a 'bypass' makes things worse; instead, use a smaller main cap. Be aware that people expecting an improvement are likely to hear any change as an improvement even when it is actually a minor degradation.
This site has a bit of a rep as the stomping ground for pedants who can't tolerate differing opinions... so many topics are divisive here.... but the advice you've had is good - a big electro will do fine in your case.
A big electrolytic cap will eventually become inductive and may also exhibit increasing frequency dependent ESR. When a small cap is added in parallel, it is true that at some frequency there may be a parallel resonant circuit with high series impedance. Far from resonance net series impedance of the parallel network is likely to be smaller with the parallel cap present.
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This is certainly not the most extreme in that regard. Also, things have changed a lot during the time I have been here. The worst of it seems to be a thing of the past. Don't find it unreasonable now myself.
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The nice thing about this site is that you do get different answers to the same question; some of them may even be right. Some people, perhaps more used to sites where one view prevails, find it difficult to cope with this.Hugh Jazz said:
That is trivially true below the main cap series resonance (where you don't need a parallel cap) and generally untrue above this resonance (where the parallel cap was presumably intended to improve things). Only when you get up into RF frequencies may the parallel cap do anything useful - but not for an audio coupling cap.Markw4 said:
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