kevin gilmore

what i want is front end complementary jfets. Don't care if they are surface mount.

schematic http://gilmore.chem.northwestern.edu/kgsshvproductiondual.pdf you definitely want global on both, or local on both. and the output dc will drift a bit. i would use the jumper block you typically find on pc motherboards. .1 inch spacing. There should be miniature switches for pc mount that would also work. (remembering that the pointer works in the other direction) make sure they can handle 500 volts.

You populate all the resistors, there should actually be 2 more (I will look later) And then 2 x 3pin jumper blocks. Then you can switch between the two (not with the power on) There might be a schematic

the nitric acid blank (i used the cheap stuff) http://gilmore.chem.northwestern.edu/blanknitric.jpg the nitric acid blank over the sample http://gilmore.chem.northwestern.edu/full.jpg the expanded sample alone actually saturated the detector http://gilmore.chem.northwestern.edu/transistor.jpg Its so nice to have an ICPMS laying around

They are either liars, or completely incompetent or both. 4 years to make a p-channel jfet, yeah right. Or there are huge quantities of 2sk389 and 2sj109 somewhere that none of us have access to that are preventing lsj109 from being released. Ayre evidently has 10's of thousands of parts in stock, yet stax had to resort to glueing singles together recently. Even the singles are not available.

i sure wish some company (any company) could supply current manufacture complementary jfets. Then things would be so much easier.

That is what i want to acomplish.

The posted front end with a lower power output sage makes a kickass Unbalanced preamp. Still trying to match this performance in a fully balanced version

So this one kind of came out in the mix. http://gilmore.chem.northwestern.edu/nfd.pdf unbalanced in, unbalanced out, about 8 watts into he6 gain programable with a single resistor (use a really good one) and Thd < .01% seriously sweet sounding. will start on the board soon.

when i have time i will fix the ground plane issue around the caps.

wiring the transformer to the low voltage supplies with the center tap in the wrong place is definitely going to cause the caps to over voltage.

the joys of 35 year old gear with dirty switches... Finally got the higher voltage range working, but did not take pictures. Never did get the trace blanking working. 50 volts per division horizontal, .5ma per division vertical 20 ua base current per step. Horizontal and vertical flipped so it looks like a npn. The first 3 are known real http://gilmore.chem.northwestern.edu/dsc_0316.jpg http://gilmore.chem.northwestern.edu/dsc_0317.jpg http://gilmore.chem.northwestern.edu/dsc_0318.jpg the next 3 are http://gilmore.chem.northwestern.edu/dsc_0319.jpg http://gilmore.chem.northwestern.edu/dsc_0320.jpg http://gilmore.chem.northwestern.edu/dsc_0321.jpg So other than beta being lower, sure look to be the real thing. High voltage tests, all of them break down between 650 and 700v will measure capacitance later.

Definitely alive and very busy with work. Same with me. Hopefully this will change for both of us Soon

That's basically a BH Kerry has a slightly different design with the kgsshv input stage, The active battery and the t2 output stage.

you haven't said what you think about the sound... i'm assuming you like it??

you do have a seperate filament transformer winding for every top tube right?? if not, arcy sparky. and if those windings are not rated for 500V+ then also arcy sparky.

well there is the single ended version with 300B, (2 per stereo amplifier) and then there is the push pull version. (4 per amplifier) just in case you have any money left over after you build the first one.

I think that a curve tracer or a specifically designed test circuit is the way to go. What i am really looking for is a 500 series tektronix curve tracer, i will ask around in a few hours. If the curves are close and the BC capacitance is right, then even if they are fakes, they are usable. But the ROHM parts should be an exact substitute except they are surface mount only. The problem with the cheap curve tracers is that they don't go up to the high voltages. I put in a bid on a tek 577 thats local to me, so everyone stay away and we will all benefit.

Its pretty much self balancing unless the tubes are way off. initial testing on various tubes, the output voltage is +/-5V

Its a operational transconducance amp, and the load is 105 ohms. Increase to 500 ohms for 10db of gain. add pot after the 105 ohms and then a buffer.

here is another one i like, buildable with currently available parts http://gilmore.chem.northwestern.edu/fcnf.pdf input can handle 10 volts peak to peak, its another operational transconductance amp. input can also handle 2 volts of common mode or differential mode offset with 0 volts dc output, something just about no other circuit can do. No feedback, and distortion approaching .01%. Flat to about 500khz. Needs +/-45 volt power supplies, and plenty of heatsinks. Otherwise cheap to build. Add a unity gain output buffer (2 of them) and set the gain with 2 resistors (or a 3 position switch) and a constant impedance attenuator and have something very slick.

http://gilmore.chem.northwestern.edu/kgitsoch.pdf An even sweeter way to do unbalanced/balanced to balanced.

The input tube filaments for the T2 are also very close to the inputs. grounding one side of the filaments takes care of the problem. inside the tube the grid is a fraction of an inch from the filament anyway.

I paid $290 for that with shipping. I don't remember how much of it was shipping, but it sat in customs for 4 days, then took 8 days to go from NY to Chicago. Those white covered things are heavy. I'm giving some of them away as christmas presents, as there is nothing in chicago anything like this stuff. At least it got here in fresh condition. Due to lots of butter and booze. Last year birgir sent me 1 of each. That got me hooked. Birgir definitely knows how to increase sales. Birgir should start selling more of this stuff outside iceland.

35 of those are bigger than a mini fridge.