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i'm on a roll... the kgsshv

kevin gilmore

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For the zener string that form the 580V pro bias, what wattage of zener should I get? 


I can do , +200, +200, and a +180 to get 580V can't I? 


Oh the PCB has 4 zeners on it (3x 150V + 1x 130V), so I guess I will have to short it if I want to have only 3 zeners.


Or I could just do 4x 100V + 1x 180V.  ::)

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1W is more than enough and any combination will work as long as the end result is 580V.  We chose those values as the board already had a lot of 150V units. 


If you jumper a trace, do it on the back to prevent arcing to the ground plane. 

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Any other tips and guides, or must-do, for the 500V version, apart from those listed here on Lil Knight's blog?




Where can I find the LT1021-10? It's a 10V reference isn't it? What are the alternatives?


What about this:



Datasheet is here:


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Quantity available is shown as 0 for now. If it's just a 10V reference, I can always find an alternative, with the same package (PDIP-8 ) and same pin outs. The pin outs are almost like that of an op amp.

REF102CP (http://www.ti.com/lit/ds/sbvs022b/sbvs022b.pdf) has a min output voltage of 9.9975V to a max of 10.0025V. Not sure how it'd compare to the LT1021-10 (http://cds.linear.com/docs/en/datasheet/1021fc.pdf) though.


Also, will it make a difference in sound if I use 12x 2sc4686a vs using all IXTP01N100D?

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I've got 1 2sc4686 without the A and collector to emitter voltage is 1000v and the 4686A is 1200v. Compared to the datasheet to death and that's the only difference between the two that I could find. Not sure about the fluxcapacitance though.  ;D


Speaking of RK50 pots, is this an RK50?



Edited by DefQon
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That's where I bought mine from (as shown in ) and I now have some more on the way. However, the batch numbers in the listing picture and the ones I got are (very) different and the available quantity keeps changing. Most likely this is a seller buying up various leftover components from manufacturers in China and so there is some risk that you don't get what you pay for. Also, in my naivity I bought some 2SK389s from the same seller and they were clearly fake (tested as BJTs and not FETs) but the listing very clearly said "genuine Toshiba" so I would not unconditionally recommend this seller.



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if you have the latest boards with the zener protection you can replace the 3rd stage bottom and top of

the 4th stage with 05n100m (latest on board version)


or solder the zeners on the back

schematic was never updated


I have never actually seen 2sc4686. only 2sc4686a which is a 1200v part


So I could replace Q1, Q2 which are 2sc4686a and Q11, Q12 which are 2sc2705 in this schematic, to IXTP05N100M? Is there any merit changing to the IXYS part?




I haven't received my onboard PCB yet, but since it's from Lil Knight, I'd guess it should be the latest. I will have to check if the zeners are there.

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I have about 15 pieces 2sc4686a coming, should I keep and use 12 of those, or should I replace them with the IXTP01N100D?


I guess I will have to measure them and see if I can find matching pairs.


In the grand scheme of things, does it even make that obvious of a difference in sound, between using the EOL BJTs, vs the MOSFETs?

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