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kaatskit:capacitors [2017/03/08 11:48]
aldavis [Capacitors]
kaatskit:capacitors [2018/02/07 03:01] (current)
aldavis [Capacitors]
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 {{:kaatskit:cap-np.png?300|}} {{:kaatskit:cap-polar.png?300|}} {{:kaatskit:cap-bipolar.png?300|}} {{:kaatskit:cap-np.png?300|}} {{:kaatskit:cap-polar.png?300|}} {{:kaatskit:cap-bipolar.png?300|}}
  
-For all three examples, the circuit is a simple first order high pass filter, like the usual interstage coupling capacitor.  Series capacitor, shunt resistor. The blue waveform is input, the red waveform is output.  The only difference between them is the type of capacitor.+For all three examples, the circuit is a simple first order high pass filter, like the usual interstage coupling capacitor.  Series capacitor, shunt resistor. The blue waveform is input, the red waveform is output.  As you can see, the output is lower in level and is phase shifted, compared to the input.  This is what is expected of a high pass filter.  Comparing the three, the only difference between them is the type of capacitor.
  
-Polar capacitors are significantly nonlinear when the DC bias is close to zero, especially when the voltage across goes both positive and negative with signal.  They have very high leakage when reversed.  You might think of it as being like a diode across the capacitor.  This can add significant distortion on very low frequencies.  It is tempting to use tantalum capacitors instead of aluminum for longer life, but they are more nonlinear so the low frequency distortion is worse.  Putting this in perspective, it's really only the very low frequencies that are being partially filtered by the capacitors.  You may hear it as a change in sound of deep bass, or you may not notice, which is why the competitors get away with it.  +Polar capacitors are significantly nonlinear when the DC bias is close to zero, especially when the voltage across goes both positive and negative with signal.  They have very high leakage when reversed.  You might think of it as being like a diode across the capacitor.  As you can see, this can add significant distortion on very low frequencies.  It is tempting to use tantalum capacitors instead of aluminum for longer life, but they are more nonlinear so the low frequency distortion is worse.  Putting this in perspective, it's really only the very low frequencies that are being partially filtered by the capacitors.  You may hear it as a change in sound of deep bass, or you may not notice, which is why the competitors get away with it.  
  
 In new equipment, you only see this at very low frequencies, around 1 Hz or lower.  As the caps age, capacitance decreases, nonlinear leakage goes up, the cut off frequency goes up, the bass response becomes weak and distorted. In new equipment, you only see this at very low frequencies, around 1 Hz or lower.  As the caps age, capacitance decreases, nonlinear leakage goes up, the cut off frequency goes up, the bass response becomes weak and distorted.
kaatskit/capacitors.txt · Last modified: 2018/02/07 03:01 by aldavis
 
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