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Thread: Charge coupled 3113B

  1. #1
    hector.murray
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    Charge coupled 3113B

    In a charge coupled 3113B, how critical is the 4 MFd cap in the HF circuit? Will a pair of solen 8.2 MFds' in series be OK? The target tweet here is an 066.

  2. #2
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    Hi Hector,

    - Theoretically ; a 10uf in series with a 6.8uf cap will give a 4.04762uf final value.
    This is ( theoretically ) a tighter tolerance than using twin 8.2uf caps . These are all available Solen values .

    - I do read your question as one about tolerances.

    ie; the .1 uf equates to 2.5% tolerance / which is less than the 5% figure given for the Solen cap . For me , that would usually translate into not fussing over it.

    - I usually take the 5% figure / add it to the stated design spec. and then figure out what the new crossover frequency might be if the the cap varies up or down by 5%. It's usually an exercise in academics and what ifs' . I'm usually looking to see how large the "musical interval" might be with new points caused by variations in cap values.

    - It's worthwhile for everyone to test their own sense of hearing to determine if they can hear ( or sense ) smaller than 1/3 octave increments . This will determine the "real need" to perhaps measure each & every cap in value / which would be necessary to truly "dial in" a network

    - Solen caps are very inexpensive . This price break allows a person to buy many extra caps and then test them ( & then match them ) for identical values .

    ( I think I need another coffee for a little more coherence )

  3. #3
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    Net Capacitance

    For those not following the math in the above post ;

    For Series Capacitors ; the Net Capacitance can be found by adding up all the reciprocals of the stated whole number values.

    Reciprocals are 1/x ( this is a function commonly included on most calculators )

    An example with 3 caps & then 2 caps ;

    (a) 3.0uf , 6.8uf, 10uf ,,,, The net capacitance is ????

    - the reciprocals of the above values are ; .333333333 ,,, .147058824 ,,, .1000
    - Total of the reciprocals is .580392157 .
    - Turned back into a whole number that becomes 1.723 uf ( rounded up )

    (b) 6.8uf , 10 uf ,,,, The net capacitance is ????

    - the reciprocals of the above values are ; .147058824 , .1
    - Total of the reciprocals is .247058824 .
    - Turned back into a whole number that becomes 4.04762 uf ( rounded up )

    (c) A 4uf Target Capacitance.
    - Already own a 12uf cap that must be used ( say for economic reasons )?
    - Then what value should the additional serial cap be ?

    Reciprocals ; 4 = .25 , 12 = .083333333

    - Answer is found by ; .25 minus .083333333 equals .16666666(7)

    - or 6uf (turned back into a whole number)

    - This answer probably surprised a few who thought the math worked some other way .




  4. #4
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    Quote Originally Posted by hector.murray
    Will a pair of solen 8.2 MFds' in series be OK?
    Maybe... depends on their actual measured values. Like Earl said, measure and match them. I think places like Madisound will do that for a little extra cash. I've already bugged Parts Express about it and they've said they have a plan to offer the service. The more people bug them about it the more likely they are to implement it.

    An example of what to do with those spreadsheet packages -

    This matrix is for Solen capacitors.

    Mine is too big to post here due to file size limits.
    Attached Images Attached Images  

  5. #5
    hector.murray
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    Thanks guys

    I appreciate the responses. It was a question of tolerances. And the answers I got were awesome. I'll try both. My trips to St-Hubert are becoming quite fun.
    Giskard, what's your favorite flavor of coffee. I'll send you some.
    Earl - you up for some coffee too?

  6. #6
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    Hi Hector

    Earl - you up for some coffee too?
    Thanks / I love coffee / but don't bother sending it across the US/Canada border .

    - That'll just kick in somebodies "knipchien filter" .

  7. #7
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by hector.murray
    I'll try both. My trips to St-Hubert are becoming quite fun.
    Earl - you up for some coffee too?
    Euh... in my modest contribution

    I talk with Cristian of Solen to question tolerance and is explain the industry is never give more if necessary so almost time the cap is under value not over...

    Maybe you help...



    Jean.

  8. #8
    Senior Member Guido's Avatar
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    I used two 8.2uF caps and are fine with this.

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