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 8th December 2012, 04:52 PM #11 DF96   diyAudio Member   Join Date: May 2007 After the pot would be better, between the slider and R1. The value would depend on how big you are prepared to go with the other electrolytics. The basic idea is that the input LF rolloff, set by the cap and R1, is higher in frequency (by a factor of 2-5?) than the output rolloff, set by C4 and your headphone resistance. Also the cathode decouplers. You also want the White follower to work properly, so the input cap should be less than C2.
 8th December 2012, 05:05 PM #12 merlin el mago diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe 0.22uF or 0.1uF can be enough? how to know the reduced value for output cap?
 8th December 2012, 05:10 PM #13 DF96   diyAudio Member   Join Date: May 2007 CR first-order high pass filter. Use a calculator, or simply build the circuit as it is. Modding a circuit may require understanding and arithmetic.
torrence
diyAudio Member

Join Date: Feb 2008
Location: Oregon
Quote:
 Originally Posted by jam First-order continuous-time implementation Figure 1: A passive, analog, first-order high-pass filter, realized by an RC circuit The simple first-order electronic high-pass filter shown in Figure 1 is implemented by placing an input voltage across the series combination of a capacitor and a resistor and using the voltage across the resistor as an output. The product of the resistance and capacitance (R×C) is the time constant (τ); it is inversely proportional to the cutoff frequency fc, that is, where fc is in hertz, τ is in seconds, R is in ohms, and C is in farads.
The natural frequency is proportional to 1/(RC) which is radians/second. You need a factor of 2 pi to get this in units of Hertz. In other words, fc = 1/(2 pi RC).

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by torrence The natural frequency is proportional to 1/(RC) which is radians/second. You need a factor of 2 pi to get this in units of Hertz. In other words, fc = 1/(2 pi RC).
Using 220nF
fc= 1/(2 pi X 1000000 ohms X 0.00000022 farads) = 1/1.38 = 0.72Hz

 8th December 2012, 06:31 PM #16 DF96   diyAudio Member   Join Date: May 2007 Yes, 0.22uF and 1M give LF rolloff at 0.72Hz. A smaller cap might be better.
 8th December 2012, 06:38 PM #17 Vincent77   diyAudio Member     Join Date: Jan 2011 Location: Bruxelles For 300 ohm headphones, a 47µ film capacitor on the output does the job. Fc(-3dB)=11.3 Hz Last edited by Vincent77; 8th December 2012 at 06:41 PM. Reason: cutoff f
Vincent77
diyAudio Member

Join Date: Jan 2011
Location: Bruxelles
Quote:
 Originally Posted by Stixx Here you go... But when you want my opinion you'd better spend the money on output transformers than trying to pass the audio signal through humongous film capacitors.
There is something I don't like about that schematic. You are using fixed (LED) bias without a CCS load and with a 1M grid resistor. You risk instability.

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by Vincent77 For 300 ohm headphones, a 47µ film capacitor on the output does the job. Fc(-3dB)=11.3 Hz
47uF film cap as output gives me 112.88Hz not 11.3Hz

 8th December 2012, 07:05 PM #20 DF96   diyAudio Member   Join Date: May 2007 47uF with 300 ohms is 11.29Hz

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