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Thread: Charge Coupling on the Cheap

  1. #1
    Senior Member Ian Mackenzie's Avatar
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    Charge Coupling on the Cheap

    Thought you guys might be interested in this effort ...hope you can make sense of this..

    This afternoon I completed one channel of my first charge coupled network.

    I decide to use the existing 2122H mid section of the 3145 network..charge coupled and the Hf and uhf section of the 4344mk11 network per the schematic charge coupled as I had those chokes in my workshop.

    Also picked up two bags of surplus (100 qty) 250volt 2 uf mains rated capacitors (polypropylene?) for 10 bucks at my diy shop and paralleled them up to make up the values and bypassed them with 0.01 uf polystyrenes.

    Initially impressions are promising. Plan to build up the other channel in a day or two.

    Me thinks its the way to go for a nice low cost network. The most expensive part is the copper foil..left overs from diy Geortz cables!

    This is just mock-up network for evaluation.......so don't cringe too much about the construction

    cheers

    Ian

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  2. #2
    Senior Member Ian Mackenzie's Avatar
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    Well I completed the other channel and had a good listen this morning.

    One interesting point is that the 4344M11 HF and UHF filters are virtually a drop in alternative for the 3145 network HF and UHF if you have 8 ohm DR82425 diaphragms like me.

    I did not have to tweak the L Pads at all.

    I think it is very nice, smooth without any noise or obvious grit in the background. Almost a damped controlled quality about the sound.

    Maybe not quite the timbre ,transparency and attack I have heard previously but very good.

    I certainly applaud the charge coupling for a high value for money crossover network.

    My thinking is charge coupling helps tame the titanium diaphragms which can otherwise sound a little hot with less so capacitors ( I also read in a capacitor comparison review some capacitors just don't work with titanium/aluminium domes or drivers..)

    Ian

  3. #3
    Senior Member Ian Mackenzie's Avatar
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    Ah...

    I bit more investigation

    The capacitors...what I found essential was getting the bypass capacitors correct.

    With the main capacitors (2uf 250 volt mains poly) I am using I found bypassing with 10,000 pf polystyrenes works well.

    However the HF filter still needed help in the mid transients so I added 0.047 polypropylene bypass caps but I found I had to keep the 10,0000 pf polystyrene caps in there otherwise the horn would not blend properly with the slot (bypassed with 10,000 pf polystyrene).

    Therefore its probably best to stick with a known recipe that works in order to get the goods . The charge coupling cleans it all up but it would seem it can't replace what's not there in the first place.

    I figure this is what you pay for when you go for the dollars and buy into premium crossover capacitors like Hovlands, Auricaps and Mundorf Supreme's etc.

    But of you are prepared to play and have plenty of time on your hands for less than 1/2 the outlay you may come close to the expensive capacitors.

    The purist may prefer to opt for the exotic capacitors but that's what makes the mystic and romance of hi end audio.

    Ian
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  4. #4
    Senior Member spkrman57's Avatar
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    Good info here Ian!

    That should give some DIY'rs something to build on.

    Ron

  5. #5
    Senior Member Ian Mackenzie's Avatar
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    Hi Ron,

    Well that was the intention.

    Its like many things in life.....seeing..or should I say hearing is believing.

    There are some things that just defy measurement and you wonder why it sounds so good for what it is.

    There is an explanation on the library product profile pages and also on one of the JBL consumer product brochures

    Of course those akin valve pre amp power amps will know that in most a/c coupled stages the coupling capacitor is in effect biased (charge coupled) by a high voltage dc potential difference and the capacitors are often exotic film foil types but audio buffs still complain about the capacitors......in the signal path...God bless their souls....

    I like trying new ideas and having recently built and shipped a high end external crossover for a member this gave me the perfect opportunity to put something simple together for my JBL 4345's before I start work on my next assignment for another member...commissioning a large scale active crossover. So there seemed little point in building up another expensive network while I will be using my own system to test a quad active crossover.

    Prior to this simple project I have built several elaberate passive crossovers. One using budget metalised polypropolyene capacitors which I grew to hate after building another version using Hovland Musicaps and more recently an external network using the highly regarded Audience Auricaps.

    The crossover network is the heart of any great loudspeaker so treat it with the care and attention is deserves when considering your next diy speaker project.

    Incidentially, the images below would involve twice as many capacitors if charge coupled so allow plenty of real estate and book time during your next vacation.

    Ian
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  6. #6
    norealtalent
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    Looks nice Ian. I must admit I envy those with a working understanding to build rather than my minimal knowledge of following directions. It is encouraging to see the building and tweaking process of these things. I gain a little better comprehension of "how it works" everytime an explanation is given. Thank you.

  7. #7
    Alex Lancaster
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    Ian: I wish my Fúps would look as good as Your mockups, cheers, Alex.

  8. #8
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    Yes, thank you. Illuminating.
    Out.

  9. #9
    Super Moderator yggdrasil's Avatar
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    Thanks for sharing Ian.


    Will try a charge coupled network for my Sovereigns later this winter.
    Johnny Haugen Sørgård

  10. #10
    Senior Member Ian Mackenzie's Avatar
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    Remember to double the value of the existing capacitor and connect two of these values in series and feed the node nine volts via a 2 meg ohm resisters.

    Ian

  11. #11
    Senior Member frank23's Avatar
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    hi ian,

    would it be possible to work with low and high resistors to feed the 9V through?

    when starting it up, you could use the low resistor value to charge the caps quickly and then switch to the high resistor to maintain the charge, but not drain the battery

    I have read elsewhere that charge-coupled-networks need time to charge the caps and this would be a way of getting the system "up" quicker for AB testing

    though, in fact, AB-ing with and without battery would be an unfair test, because without charge-coupling, you would use ony half as many caps in your signal

    I prefer paper-in-oil capacitor, but they would be a little large for doubling with charge-coupling. The one in the picture is a 4uF 2000V Sangamo.

    frank
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  12. #12
    Senior Member Ian Mackenzie's Avatar
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    I am not sure.

    Either way the capacitors would take time to discharge so to do a proper (immediate comparison) you would need to build a non charge coupled network using identical capacitors.

    The battery should last its shelf life so there is no concern leaving it on all the time.

    Regards paper and oil capacitors they have as a rule such a strong signature that charge coupling is unlikely to have a significant impact. My understanding is the oil acts to damp the capacitor, that and other characteristics give them a particular character preferred by some.

    I think it would be worth your while (for only a small outlay) to obtain some good quality caps, bypass them with 0.01 uf Theta Audiocaps in charge coupled format and compare with your paper and oil crossover.

    ..see this post for ideas
    http://www.audioheritage.org/vbullet...0&postcount=13

    http://www.audioheritage.org/vbullet...4&postcount=45

    I might try these next, they are reasonable priced, are available locally and appear to be used by some reputable loudspeaker manufacturers.

    http://www.claritycap.co.uk/SA.html



    Ian

  13. #13
    Senior Member briang's Avatar
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    I need to learn...

    OK, so I read the whole thread and have no idea what's going on...any chance there is a primer someone can recommend that I might read to do some remedial catch up work?
    Paying debt to Karma...

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  15. #15
    Senior Member Rusnzha's Avatar
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    Originally Written by Ian Mackenzie

    There are some things that just defy measurement and you wonder why it sounds so good for what it is.
    I rebuilt the crossovers in my L100s as charge coupled. I used Solens for the main caps and bypassed with .01ufd Theta caps. The most surprising benefit was how the low end tightened up. Since the woofers are wired stright from the inputs, I am curious why this should make such a difference.

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