Doubt on plarised cap vs non polarised

[rs1026]

What happens when we change the non ploarised 4.7uf in Rod's circuit here http://sound.westhost.com/project48.htm

to polarised electrolytic.I feel polarised may be better since it will block the dc from previous stage.


I have also noticed in these threads that polysterene caps are beter for audio contruction.Why is it so?

Any expert comments?

[Mr Evil]

Using different capacitors won't make a difference to their DC blocking ability.

If you use polarized ones, they may fail quite quickly if there is significant DC and it is not in the right direction. A better choice if you want improvement would be to use a non-electrolytic capacitor, such as polypropylene or polyester film.

Polystyrene capacitors are good because they have low dielectric absobtion and are very stable, which makes them closer to an ideal capacitor compared to most other types. However they also tend to be larger than other types, quite expensive in larger sizes, and you'll never be able to find any as large as 4.7uF, if you were thinking that.

[carlmart]

There was an article series on capacitors some months ago in Electronics World & Wireless World, where the author offered some measurements to prove that a non-polarized electrolytic and even a series of non-polarized electrolytics were better than polarized types. Of course I am talking of DC blocking, not PS applications.

Non-polar electrolytics seemed recommendable at the input and at the feedback, if you can't afford a film type or size is too big. Probably some polarized Black Gate users will say different.


Carlos

[Lars Clausen]

RS1026: In my op using a PP cap in a subwoofer filter would not give you any sort of improvement. It would be hard to fit in the small board, and probably expensive.

Further you will certainly never have to block more than a few mV, so any normal polarized (electrolytic) cap will work just fine.
Your own suggestion will be completely OK.

Use a 25 V or greater just to be sure. It can withstand up to 7-8V in the wrong direction.

It seems a bit odd tha Mr. Elliot places C1 in his circuit to avoid crackling noises when turning VR1A, caused by DC offset in U1A, and C3 to avoid cracling noise from VR1B. After that nothing.
What about VR2? It could also make noises if there was any DC offset on U2A + U2B. Also the phase shift sw could make some pops if any DC was present.

Best wishes

Lars

[carlmart]

Originally posted by Lars Clausen
RS1026: In my op using a PP cap in a subwoofer filter would not give you any sort of improvement. It would be hard to fit in the small board, and probably expensive.

Further you will certainly never have to block more than a few mV, so any normal polarized (electrolytic) cap will work just fine.
Your own suggestion will be completely OK.

Use a 25 V or greater just to be sure. It can withstand up to 7-8V in the wrong direction.

It seems a bit odd tha Mr. Elliot places C1 in his circuit to avoid crackling noises when turning VR1A, caused by DC offset in U1A, and C3 to avoid cracling noise from VR1B. After that nothing.
What about VR2? It could also make noises if there was any DC offset on U2A + U2B. Also the phase shift sw could make some pops if any DC was present.

IMO those capacitors are there to block interstage DC, not to avoid crackling noises. Particularly when the pot are in series.

It would be better to use non-polarized types, I think, even if they were as two-polarized series.

A film type would do fine too, but as we are dealing with low frequencies here it would do fine to use a good 'lytic.


Carlos