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Old 8th December 2012, 03:52 PM   #11
DF96 is offline DF96  England
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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.
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Old 8th December 2012, 04:05 PM   #12
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0.22uF or 0.1uF can be enough? how to know the reduced value for output cap?
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Old 8th December 2012, 04:10 PM   #13
DF96 is offline DF96  England
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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.
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Old 8th December 2012, 04:16 PM   #14
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Quote:
Originally Posted by jam View Post
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).
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Old 8th December 2012, 05:11 PM   #15
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Quote:
Originally Posted by torrence View Post
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
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Old 8th December 2012, 05:31 PM   #16
DF96 is offline DF96  England
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Yes, 0.22uF and 1M give LF rolloff at 0.72Hz. A smaller cap might be better.
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Old 8th December 2012, 05:38 PM   #17
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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 05:41 PM. Reason: cutoff f
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Old 8th December 2012, 05:47 PM   #18
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Quote:
Originally Posted by Stixx View Post
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.
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Old 8th December 2012, 05:57 PM   #19
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Quote:
Originally Posted by Vincent77 View Post
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
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Old 8th December 2012, 06:05 PM   #20
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47uF with 300 ohms is 11.29Hz
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