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torrence
diyAudio Member

Join Date: Feb 2008
Location: Oregon
Quote:
 Originally Posted by merlin el mago Using 220nF fc= 1/(2 pi X 1000000 ohms X 0.00000022 farads) = 1/1.38 = 0.72Hz
This is correct, although note that at the critical frequency the power is already attenuated by half. Most people try to keep away from the critical frequency by a factor of 5-10 if they can. So if the lowest tone you want to reproduce is 20 Hz, a critical frequency of 2 Hz is safe. Since capacitors can often vary by a factor of 2 from their 'nominal' capacitance, this also gives some safety margin for component variations.

So either a 0.1 or 0.22 uF cap is probably fine here.

 8th December 2012, 07:10 PM #22 merlin el mago diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe @Vincent77 @DF96 I'm sorry, how do you calculate? I use V-Cap output capacitor Coupling Capacitor Calculator by V-Cap
torrence
diyAudio Member

Join Date: Feb 2008
Location: Oregon
Quote:
 Originally Posted by merlin el mago @Vincent77 @DF96 I'm sorry, how do you calculate? I use V-Cap output capacitor Coupling Capacitor Calculator by V-Cap
This calculator gives you the -3db frequency as 11.29 Hz, but as I said, you typically want to avoid this by some factor. They have just arbitrarily multiplied by 10 to give the 'optimal response' at 10 x fc.

This site appears to be oriented towards people who cant do simple math, which is probably a good functional definition of an 'audiophile'...

 8th December 2012, 07:17 PM #24 DF96   diyAudio Member   Join Date: May 2007 I calculate with my old Casio fx-570 calculator.
merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by torrence This is correct, although note that at the critical frequency the power is already attenuated by half. Most people try to keep away from the critical frequency by a factor of 5-10 if they can. So if the lowest tone you want to reproduce is 20 Hz, a critical frequency of 2 Hz is safe. Since capacitors can often vary by a factor of 2 from their 'nominal' capacitance, this also gives some safety margin for component variations. So either a 0.1 or 0.22 uF cap is probably fine here.
Thanks, now the question is: if I use input cap 0.1 or 0.22uF how can calculate the lower value to the output cap?

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by DF96 I calculate with my old Casio fx-570 calculator.
I supposed you used a electronica calculator but I want to know the formula to learn how to calculate by myself.

 8th December 2012, 07:23 PM #27 DF96   diyAudio Member   Join Date: May 2007 See post 14, which you apparently used correctly in post 15. Or see any electronics textbook, or use Google - I told you the name of the circuit in post 13. Do you really want to be spoon-fed?
tinitus
diyAudio Moderator R.I.P.

Join Date: Nov 2005
Quote:
 Originally Posted by merlin el mago the schematic uses 470uF 350V, really is necessary so big or I can use a small film cap like 27uf or 10uF or less?
the capacity value have been covered well
but maybe it should be noticed that a big volume can size also have lower resistance(ESR)

a good film cap with that value is exstreme
if you have loads of money, you could order a large stack of Duelund caps

but maybe you can find a nice quality bipolar cap
or even a 'motor run' type cap might work well

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by DF96 I calculate with my old Casio fx-570 calculator.
Quote:
 Originally Posted by DF96 See post 14, which you apparently used correctly in post 15. Or see any electronics textbook, or use Google - I told you the name of the circuit in post 13. Do you really want to be spoon-fed?
Ooops DF96 you are right

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by tinitus the capacity value have been covered well but maybe it should be noticed that a big volume can size also have lower resistance(ESR) a good film cap with that value is exstreme if you have loads of money, you could order a large stack of Duelund caps but maybe you can find a nice quality bipolar cap or even a 'motor run' type cap might work well
Please read carefully all thread, I learned a lot with the kind people helping me to understand & calculate.

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