kevin gilmore

so it turns out the hawksford already came up with the idea of cascading a current mirror (well sort of) http://www.essex.ac.uk/csee/research/audio_lab/malcolmspubdocs/J10%20Enhanced%20cascode.pdf it also turns out that the single ended version where you ground the input, and then drive the emitters makes an absolutely wonderful I/V converter for your favorite dac. also previously released in a simplified version by pedja rogic. http://gilmore.chem.northwestern.edu/privstage.pdf so the building blocks are now piling up. need a really sweet output stage (not the headphone kind) and this preamp should be able to compete with the big boys.

the stuff i used was custom made for the military and is pure silver. not going to try to buy more of that.

This is instead of the multiamp board. Input switching This board Pot of some kind Diamond buffer output There is nothing wrong with the multiamp, in fact it sounds great too. But the input impedance is lower due to supersymmetry. The idea on all of these is to eventually replace with jfets once they become available. As it is, this new board is without feedback of any kind, and is faster and more quiet. plus gain is a single resistor and compensation is unnecessary.

first cut at the board http://gilmore.chem.northwestern.edu/ubaltobald.jpg

Gore will happily make you anything you want. Minimum of 5000 feet. You will not like the price. I use 50 ohm cable.

updated schematic with servo http://gilmore.chem.northwestern.edu/kgsshvproductiondual.pdf

here is the unbalanced/balanced to balanced front end. http://gilmore.chem.northwestern.edu/ubaltobald.pdf really sweet sounding. 0 db of gain balanced, -6db of gain unbalanced. gain is controlled by R5,R32 so i could put a relay in that switches the gain to maintain 0db (or any other number) when you switch from unbalanced to balanced. still even better with the that340 replaced with jfets. mpsw06,mpsw56 replace 2sc2240/2sa970 when we can't get them.

i have known about this for a while. Its about 4000 sq feet of stuff. There is a few pieces i would be interested in, but very little of this stuff is actually useable these days. I would love a mint hammond organ with 2 tone cabinets and 2 leslies. (not sure how i would get it in the basement)

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.