electro caps doubt atfter research

[garfo]

so,after a while of getting into electro caps understaning,i have more and more doubts.in some places  was under the idea that some caps like the Pans FC/FM or Elnas will perform better on a 9v circuitif they are highly rated on voltage such as 100v.yet,on other articles i have read that capaitors overly rated on voltage will loose capacitance properties when opperating on a lets say 9 v circuit.
Any thoughts?
Thank You un advance

[RobA]

Are you asking about using them as power supply caps or in the audio path?

[garfo]

well,since im not very sure on how to identify the audio grom the poeewrr,im not sure.but lets use exampled.on a rat, the decoupling caps are two electros rated 4.7 and 2.2.what would be the best voltage hete?im using pan fc by the way.and what about power,what is the better option?

[garfo]

so,yeah,what i mean is on audio path isi like the bigger the voltage,he better?

[pickdropper]

Not just elecros.  Ceramic caps have that as well.  Here's a good article about mult-layer ceramic caps (MLCC)

http://www.johansondielectrics.com/technical-notes/product-training/basics-of-ceramic-chip-capacitors.html

[garfo]

really,you should sere my face while reading the article.sorry for the doubt
i didnt quite get it.so my question is the same in my mind.should i use smaller voltage or bigger voltahe caps in audio path?

Not just elecros.  Ceramic caps have that as well.  Here's a good article about mult-layer ceramic caps (MLCC)

http://www.johansondielectrics.com/technical-notes/product-training/basics-of-ceramic-chip-capacitors.html

[RobA]

I've seen experiments that show that it is true with ceramics. Ceramics derate under voltage and the effect is lessened with higher voltage ratings. Although, using C0G caps where possible is even more important.

I've read it with electrolytics as well, but I'm not buying it as much. There are certainly effects that are important though. The reason I asked power supply or audio path is because the ESR of a cap is a function of the voltage rating (actual the physical size of the cap which is a function of the voltage rating). For some, but not all, power supply uses, the ESR can be important. I did testing on the various voltage booster chips and in these situations have low ESR electrolytic caps significantly increased the efficiency of the voltage converter. I found the Nichicon PS and Panasonic FR series to best of the caps I tested. I also found that using 25V, 35V, 50V of these types made no difference, but that the 25V of these outperformed 50V to 100V of other caps.

For audio path, it's up to your ears. I like the Nichicon FG series. They are relatively cheap and sound good. I imagine though that you'll find some that think they are abominations and should never be used.

The claim that I've heard on the Rat is that the critical thing is the actual match to the specified capacitance of 2.2µF and 4.7µF so that the frequencies are actually boosted where you want them to be. I think that there is some truth to this. Electrolytics have pretty broad tolerances and moving from one cap to another could change the gain with frequency quite a bit in that circuit. I haven't tried playing with this though. I've built two Rats and they both sound good. One is better than the other though. I didn't really try to figure out why and since I made one as a present, I can't really take it back and tear it apart .

I'd guess that as long as you use decent caps, as long as you match the voltage ratings that you are going to see in the circuit and apply the rule of thumb to double and then use the next biggest value, you won't see/hear much difference.

[garfo]

thanks man,bascillary double and use the next one,that's a refference.well,maybe using film for the 2.2 and 4,7  on the rat would bring me closer to the tolerance.i suppose it is ok in the rat case,right?

[RobA]

Film would be great for the circuit. But expensive and probably wouldn't fit any of the PCB layouts out there. If you have a cap setting on your DMM, you could just measure a few until you got matches.

[garfo]

my dmm has no cap testing.so i think ill just throw two pan fcs por fm since theyre the ones ive got.thank you.

[garfo]

Film would be great for the circuit. But expensive and probably wouldn't fit any of the PCB layouts out there. If you have a cap setting on your DMM, you could just measure a few until you got matches.

just one more thing.there are some 1 uf electros on the rat,would it be ok to replace them with film box in this specific case
?

[RobA]

On the Slow Loris PCB, I think the output cap is supposed to be a film cap, if I remember right.

[garfo]

Yep. will replace that one with a film box thanks