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Thread: Yup, Another One... Kraken 50 Build: Round II

  1. #36
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    Quote Originally Posted by catalin gramada View Post
    Interesting. So you're using the reservoir cap's negative terminal as a mini star node. Then sending that to ground instead of the screen cap's neg. Like this:


  2. #37
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    Quote Originally Posted by Thoriated Tungsten View Post
    I would definitely lift the grey '0' wire on the 2x 350V secondary from the star ground and have it follow A1 & A2 over to the bottom of the 220k bleeder resistor on the top filter cap. There is zero benefit to having the HT center tap going to the star ground. Right now the full ripple current from the transformer is flowing through a wire carrying signal current (the green wire from the bottom cap to the star ground).

    Note that the low voltage supply for the DC heaters does things correctly by isolating the ripple currents from the chassis ground.
    Great, thanks for the help!

  3. #38
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    Yes. Tie power cathodes at the wire between those two caps, You can use a thick solid wire between caps (or better one piece from first cap-second cap- third cap minus pole) and regular wires from power cathodes

    ground-scheme.jpg

  4. #39
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    Quote Originally Posted by catalin gramada View Post
    Yes. Tie power cathodes at the wire between those two caps, You can use a thick solid wire between caps (or better one piece from first cap-second cap- third cap minus pole) and regular wires from power cathodes

    Click image for larger version. 

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    Oh I see you're bringing the preamp ground from the bus bar to the screen filter cap negative as well, instead of directly to star ground?

  5. #40
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    that.s right. But there are also some wires you need to move to complete: inverter ground (green wire from presence cap) should be tied to minus pole of second cap and NFB return (the wire from output jack to chassis) lift from chassis and tie at the presence pot lug.
    Last edited by catalin gramada; 08-05-2017 at 06:14 PM.

  6. #41
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    Quote Originally Posted by catalin gramada View Post
    that.s right. But there are also some wires you need to move to complete: inverter ground (green wire from presence cap) should be tied to minus pole of second cap and NFB return (the wire from output jack to chassis) lift from chassis and tie at the presence pot lug.
    So, I get why—technically—these things are good to do. But there is no noise in this amp. The amp is pretty quiet already. So what exactly will these things improve?

  7. #42
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    This is a very good question. The designers spend a lot of effort to simplify the building choosing the best compromise to do a proper grounding (and you circuit have a lot)Someone clever find a way to broke the rule and made a functional circuit despite the wiring bugs. The wiring plan I presented to you guarantee the minimal noise in you circuit from a grounding point. There is no reason to change anything in you amp if you amp works without grounding issues...I don.t remember how this discusion started on...
    Last edited by catalin gramada; 08-05-2017 at 06:43 PM.
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  8. #43
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    Quote Originally Posted by catalin gramada View Post
    This is a very good question. The designers spend a lot of effort to simplify the building choosing the best compromise to do a proper grounding (and you circuit have a lot)Someone clever find a way to broke the rule and made a functional circuit despite the wiring bugs. The wiring plan I presented to you guarantee the minimal noise in you circuit from a grounding point. There is no reason to change anything in you amp if you amp works without grounding issues...I don.t remember how this discusion started on...
    hahaha understood

    There are a few things I can rewire, like the PT center tap to the reservoir cap instead of chassis ground. But there are some other compromises I have to make just due to lead dress and whatnot. The entire preamp is isolated and grounded to a floating bus bar, with one connection to the star ground. But I have the output tubes grounded locally through external bias test points. That can't change.
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  9. #44
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    I won't comment on either or,.. but would like to know if you hear any difference - since are building two!?
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  10. #45
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    Some more progress today. This is the part where everything's a hot mess lol. Redid some of the grounding as discussed. Reservoir cap neg. lug now serves as a floating star ground. That point goes to chassis ground. So just one wire to chassis for the most part. There are still one or two local grounds, but that is unavoidable. Preamp ground bus goes to screen supply neg. lug. That goes to reservoir cap neg. lug. PT CT goes to reservoir cap neg. lug. Bias pots and filament CT go to chassis ground point. Didn't wire those to the floating star ground because it would have been a cluster fuck.





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  11. #46
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    Home stretch.

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  12. #47
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    I've been swapping tone stack values back and forth and they all sound good to me. Been trying 47K, 39K, 36K, and 33K slope. So I'm thinking about using a 50K pot instead. Been trying 470pF, 510pF, and 560pF treble caps. And same deal. They all sound good for various styles of music. I might just use the 510pF for a middle of the road value. Or I might throw some caps on a switch.

    The thing is, I'm short for space on the chassis to mount the pot. I don't really use the Ceriatone "pussy trimmer". I always keep it maxed out. So I might hardwire a resistor in its place and use the mounting spot for the variable slope.

    Just want to make sure all I need to do is measure the pot when it's on 100% and use a resistor that's close to that. Typically, 2204s have a 470K to ground as part of the treble peaking circuit. The pussy trimmer is a 1M pot that replaces that resistor. Just unsure what value resistor to use since the pot's value changes depending on where the gain control is set. But I'm guessing I should just use a 1M resistor since that's the pot's max value?

    Here's a schematic:

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