FirstWatt J2

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#984
#985
2 picoDumbs said:
That's handy information.
What is Vds across and current through input jfets on your build?
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I hope ZenMode would remember or know. It has been really long time we did it. I would be glad to make a reading and let you know, but I am flying tomorrow morning on a short trip and will be back on June 14th. If Zen cannot figure it out until then, I will measure and post answer here upon my return.

If I could point on something, my problem was that I did not install in the first place the right sized LEDs, and after we corrected for it, all was fine. So read carefully about LEDs and purchase exactly the one specified.
 
#988
AR2 said:
I would also consider increasing the voltage for the higher output power (if needed). Mine is singing without any problems last several years at secondary TR voltage of 2 x 22V. The included picture is old, now it is run as dual monoblocks in identical case and with second PS.

http://www.diyaudio.com/forums/pass-labs/186848-babelfishing-mighty-ar2.html
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I think that rickmcinnis plan is to build separate psu but still utilizing same chassis. Increasing psu voltage will be toooo hot for factory chassis, unless current draw is reduced, which is not an easy task on original J2.

hmm, back to my first suggestion, keep your original J2 and build a clone if you want to jump into real DIYaudio. then you can play with manyyyy iteration and possible permutation with your wildest mind. but again as gerd has mentioned, will it be better then J2 which is cooked by the master?
 
#989
rickmcinnis said:
......

ZM - I just realized those simulations are using a stepped load for the current source. You might want to change that.
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nope , just checked - it's plain simple 1A65 CCS

rickmcinnis said:
......

Even though I see the mighty ZM holds you in HIGH regard .........
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not just that

ZM is AR2's Padawan

😉

however - important difference - what AR2 is having (as somewhat more potent iteration) is Babelfish J2 , which is having cascoded front end LTP , meaning that input JFets are having voltage (thus dissipation ,too) umbrella ; factory J2 is not having that , so upping rails voltage would be as howling a Devil , especially taking in account that in your J2 there also are JFets as small CCS for input LTP, connected across entire rail
Papa did that few times , but I wouldn't ..... me being cheapskate and woosie :rofl:
 
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#990
So the resistor input supply has a little more ripple but you lose a capacitor in a position that makes the rectifier work harder than it needs to along with the fact that the resistance makes life easier still on the rectifier.

I think that is the one I will build first.

I agree one needs to build something!
 
#991
My J2 has blowed its PSU trace for a second time on the positive rail. Besides the obvious of needing a bit more copper on the board, I would like to lower the heat a bit. Seems I need to find those four legged critters in the junk box...
 

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