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Formula For Output Capacitors

Discussion in 'DIY' started by Andrew Heck, Jul 11, 2018.

  1. Andrew Heck

    Andrew Heck AK Subscriber Subscriber

    Messages:
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    Location:
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    So, I’ve been trying to figure out the value of the output couplers on my Xiang Sheng DAC-01a and there are no schematics available anywhere and the ones that are installed are very difficult to read... Anyway, I ran across a formula based on the input impedance of the amp downstream from the DAC. It is, as I understand:

    C=1/2 (pi) (hertz at roll off) (input impedance)

    So if I have an amp with resistance of 30K ohms, and I want to roll off around 8 hertz, my output couplers should be 376,800 what? uf, nf, pf? Or is this even close to right?
     

     

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  2. audiotemp

    audiotemp Well-Known Member

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    583
    I think you want C = 1/( 2 pi f R ), which in not what you've calculated.

    Also, if f is in Hz and R is in Ohms, then C will be in Farads.
     
  3. Andrew Heck

    Andrew Heck AK Subscriber Subscriber

    Messages:
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    Location:
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    Thanks. Yes, that makes more sense.
     
  4. triode17

    triode17 Super Member

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    1,315
    I got 0.66 uF. Don't forget the "one divided by" part.
     
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  5. gadget73

    gadget73 junk junkie Subscriber

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    Sounds right without doing the math.
     
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  6. Andrew Heck

    Andrew Heck AK Subscriber Subscriber

    Messages:
    216
    Location:
    chattanooga, tennessee
    So, my amp has a frequency response to 9hrtz. I should be able to use a pair of .58uf film caps for output couplers on my DAC and maybe ditch the WIMAs in the bypass positions? If so, how much of the leads on the films is too much if I have to run them back under the caps to the original points for the electrolytics?
     

     

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  7. Andrew Heck

    Andrew Heck AK Subscriber Subscriber

    Messages:
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    Location:
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    BTW I'm very thankful for the responses and help.
     
  8. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

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