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Thread: Are These 4312a Control Monitor Crossovers?

  1. #16
    Junior Member brettMc's Avatar
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    Quote Originally Posted by grumpy View Post
    The JBL p/n (61098) for those little blue caps are polypropylene.
    No one would use ceramic caps for bypassing larger values in a crossover.

    Definitely replace the L-pads if you have them in-hand.

    If you're hell bent on replacing the caps, you could both get higher quality
    capacitors (obviating the need for the bypass caps at all), and double up
    on the values of the yellow ones and get two of each: to replace each single
    cap with a pair in series. Then introduce a dc bias voltage (9v battery works)
    through a several-Mohm resistor to the point between the caps. Google
    "charge coupled crossover" or "dc-biased crossover".
    I have often wondered about DC biasing. But since I have never done any of this sort of work before I would need some serious input from you all. Does the DC biasing just 'precharge' the caps? How could I do this and still be able to change the battery easily? Where does the battery need to go in the circuit?

    As for doubling up do you mean instead of one 10uf 250v get two 10uf 250v and wire those in series to replace the original single 10uf? Then I would assume pull the bypass cap and simply bridging that gap with wire? I am totally willing to spend $30-$40 a cap. Please share your approach.

    Thanks for your interest and time!

  2. #17
    Senior Member grumpy's Avatar
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    Question

    Quote Originally Posted by brettMc View Post
    I have often wondered about DC biasing. But since I have never done any of this sort of work before I would need some serious input from you all. Does the DC biasing just 'precharge' the caps? How could I do this and still be able to change the battery easily? Where does the battery need to go in the circuit?

    As for doubling up do you mean instead of one 10uf 250v get two 10uf 250v and wire those in series to replace the original single 10uf? Then I would assume pull the bypass cap and simply bridging that gap with wire? I am totally willing to spend $30-$40 a cap. Please share your approach.

    Thanks for your interest and time!
    Did you check google, like I suggested? Double up means 2x, or using two 20uf caps in series (in your example).

    Do not put a short where the bypass caps are/were. The battery is always in-circuit... use a connector for it of your choosing. The - battery terminal goes to ground (negative speaker terminal). The + battery terminal is connected (using large value resistors such as 3 Mohms) to each junction between the double valued caps... one such resistor per junction.

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