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stax t8000 clone (well sorta)

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I think the right part number for Q16, Q18 is PBHV2160Z.  That's what I'm seeing on the board as well. 

Q9 and Q10 should be the higher voltage version.

Everything else you've mentioned should be good :) 

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Now with top plate.     Aerial view, the two holes in front of outer small tubes are for balance trimmers. Adjust balance after some time of warm up and then insert jumpers for the ser

Well its not like the stax mafia aren't busy and we certainly are not going to do an output stage with 8ma of current, and therefore no reason for a 4 stage amp, and since tube inputs seem to be

using Kerry's servo, but a resistor to make +200 by the way the alternate name of this board will be t8000DR   (DR as in done right) edit: fixed font sizes      

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updated the board pictures, either stn9360 or 2sa1486 (people should have bunches of them, still available)

that transistor is roughly .6 watt

5 watt resistor is designed to give about 200v

3 x 68v zener in series would be around 210, so if the tube is not warm...

Edited by kevin gilmore
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2 hours ago, mypasswordis said:

Any chance to shave just a few more mm off the length of the tube input Carbon boards? Maybe on the left side the zener string has space to be moved and the traces adjusted a little? Then I would be able to squeeze it into this standard size ebay case, which has 300mm internal length: http://www.ebay.com/itm/122099811096 

length or width, you are asking for width.  for that box, inside is 6.3 x 11.8  so two amp boards would fit on one heatsink already. no room for anything else, would have to be a two box.  I centered everything on the board, so when you put them next to each other, the tubes align.

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Yeah, I guess I mean width. :) If I mounted both on one heatsink it would get very hot so my plan would be to do it lopsided, one on each side. The tubes would look a bit funny. Even putting the two boards side by side and all the way to one side there would only be 20mm left for XLR/RCA jacks and circular connector for the umbilical at the back panel, and I am measuring roughly 23mm on my panel mount XLR jacks right now so it just barely wouldn't fit. 

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It only sees a few volts, but for safety sake you might try a higher value that could cover the voltage from ground to the negative rail.

Can't wait to see how this performs :) 

EDIT:  I'm noticing that the gaps between the ground plane and traces are very narrow (not sure if I'm seeing this right).  If so, I'd recommend about .035".

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  Thanks,  there is no ground plane at all, not at these voltages.

the groves are where I cut the 2oz copper, all that's left are  traces

Just the cut (.020") would be enough for 80v but not 800v:D

don't think Kevin's board files have any planes, like the grounded grid.


  From looking at the schematic I thought that servo cap would normally not have more than 10-20v but

on start it could see hundreds, so used a 450v Panasonic,

thanks for confirming this!


  I chose this one thinking it will be more different sound wise then a tube input carbon

should have missing parts this week

Edited by congo5
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Yeah... So, I will do it with separated winding with LT1083 regulator. All floated.

I do it mainly because I plan to use separated ps box. Running AC with DC in a same umbilical cord seems somehow compromised for me.

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9 hours ago, Hopstretch said:

There's no way any current could make it all the way through you to ground, Biggie.

I think that might be true.  I'm having some truly bizarre issues with an old Stax amp and let's just say that it put 120VAC on the chassis.  I connect a source and boom!!  I got a slight tingle but that's it.  

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Yeah, I'll do some further testing with the insulation tester tomorrow.  I have the Uni-T UT-512 and who knew Uni-T made something usable?  Their meters are just garbage but this is kinda nice.  It does complain a bit at 2500V but nothing too serious. 

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