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kevin gilmore

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Everything posted by kevin gilmore

  1. kevin gilmore

    digital attenuator

    Like i don't have enough projects going on at once I'm tired of waiting for someone to release boards that do this right. so here is mine in progress http://gilmore.chem.northwestern.edu/attenuator2.jpg Because i don't like any standing power on the relays, and i don't like the resistive drive either, this had to be a bit bigger. board is 3.4 x 10 inches. stereo single board, or two for balanced.
  2. kevin gilmore

    transconductance amp

    so tyll has been going crazy over the bakoon for planars. well there are a lot of things i don't like about that amp, especially the battery power and distortion. so here is something much better, tested last night at .06%thd, no feedback, output impedance 100k which is solely due to the servo... http://gilmore.chem.northwestern.edu/currentsourceamp2.pdf http://gilmore.chem.northwestern.edu/currentsourceamp2.zip also testing curved traces
  3. kevin gilmore

    digital attenuator

    that one is indeed 3 layers, extra complete ground layer in the middle. forgot about that one.
  4. kevin gilmore

    digital attenuator

    its a 2 layer board. not sure why it is being detected as 3 layers
  5. kevin gilmore

    current feedback electrostatic amp

    so sorenb really wanted this, so here it is http://gilmore.chem.northwestern.edu/cfaelectrostat.pdf the outputs are 300v darlington transistors just need to find a suitable npn match for the stn9360, and this can be done all surface mount tiny, fully complementary, fully dc coupled, decent input impedance (none of this 75 ohm nonsense) push pull output... edit: PBHV2160ZX looks great for the npn. so you can add one more set of outputs and run up to 500v power supplies balanced input only, and you need 4 of them
  6. kevin gilmore

    current feedback electrostatic amp

    easy, low cost, no adjustments, only hv supplies etc.
  7. kevin gilmore

    The ultimate DIY? A Stax SRM-T2!

    thermal grease lasts forever. I have a jar with original Newark part number on it, and its 50 years old. Still good. the stuff contains aluminum oxide or silicon oxide, or various other compounds in silicone and for voltages less than about 2.5kv its an insulator. Although it can have more capacitance than you might think.
  8. kevin gilmore

    i'm on a roll... the kgsshv

    So for whatever reason a number of different projects are coming together at the same time. This is the latest. http://gilmore.chem.northwestern.edu/kgsshv.jpg Its the high voltage version of the kgss with higher voltage pnp transistors, a cascode current source for the 3rd stage, the lsk389 part (or singles) and much higher voltage output transistors. The result is something that runs on +/-500 volt power supplies, and is as close as i know how to do to the T2. (except fully solid state, and easy to build) The transistors that go on the heatsinks are already insulated, which makes that part easy. Not a lot more money than an exstata, and much better sound. So do i make it a single box, Do i make it a two box affair with the power supply in a seperate box... What are people interested in??
  9. kevin gilmore

    Technical Assistance/Advice Thread

    v- is actually -370v and vref3 is -350v take a closer look at the original schematic
  10. been working on this one a while, with all the popular transistors disappearing, I hope that this one won't go obsolete before the boards are out. I don't think so because Fairchild has said that the bc parts should be available for at least 5 years but onsemi said the same thing. This one is a diamond transistor input set, used as a voltage to current converter. A pair of Wilson current mirrors with input and output cascade as the VAS and a triple darlington output stage. http://gilmore.chem.northwestern.edu/cfa2.pdf if someone knows of better surface mount parts to replace the bc series, I might as well do that from the start. ft >150mhz, hfe >100 Vceo >50 etc
  11. kevin gilmore

    Hifiman Jade II

    history lesson (unless birgir says otherwise) As far as I can tell the first stax amplifier to use differential cascode circuit is the srm-1 first introduced in 1979 long before hifiman was even a company
  12. kevin gilmore

    Hifiman Jade II

    The srm-001 is an opamp driving a fet that drives a transistor (cascode) into a load resistor and is cap coupled to the output. (cascode differential) The jade2 is an opamp driving a transistor that drives a mosfet (cascode) into a load resistor and is cap coupled to the output. The calculation of output capacitance is flat out wrong as the middle of the cascode is AC ground. (cascode differential) Just about identical. Obviously the jade2 consumes a bunch more power and puts out a bunch more power. I own 2 hifiman products. Both are built like shit. I'm unlikely to buy hifiman products ever again.
  13. kevin gilmore

    Raal Requisite SR1a

    uberamp2 in single ended form. then you don't need the resistor box.
  14. kevin gilmore

    Hifiman Jade II

    The circuit is more like the srm-001 blown up by a bunch. So opamps input, solid state version of grounded grid output stage, resistor loaded, and capacitor coupled output. Positively ancient design by any standard. Did not even replace the power resistors with current sources. Saying that the output capacitance is that low because the two devices are in series clearly shows no understanding on how that design works. And the series output inductors are not a great idea either. The headphones may be decent, I don't know because I have not heard them, but there are so many decent headphone amps out there that buying the hifiman version seems like a waste of money.
  15. 2 grhv, 2 grlv78xx,2 grlv79xx, 1 main board, 1 mini t2 please
  16. kevin gilmore

    goldenreference low voltage power supply

    it may have something to do with the minimum voltage. But I have not tested it.
  17. I'm happy to report that the goldenreference low voltage dual power supply works as designed, and tests less than 1 microvolt of noise. Going to have to take it to work and put it in a screen room to really measure the noise. http://gilmore.chem.northwestern.edu/goldenreferencedual.jpg however there is one silkscreen error seen by the extra + near the 47uf cap on the right side. I will update the files shortly. All 4 of the 47uf caps need to have their plus sides pointing to the left. very happy with this
  18. kevin gilmore

    goldenreference low voltage power supply

    someone needs to check this, works as single rectifier with center tapped transformer, or a pair with dual secondaries. Up to 72vdc, perfect for GRLV caps are 100v rated, 1uf is 0805 size, 10uf is 2220 size I can certainly do a bigger version with different fets for higher currents and lower voltages. .9 x 1.1 inches syncrectifier.zip
  19. kevin gilmore


    enough people have been asking for this, we finally decided to do it. It was easy from the current layout. Best to stick with +/-400v power supplies http://gilmore.chem.northwestern.edu/kgst.jpg
  20. kevin gilmore

    goldenreference low voltage power supply

    going to make it a replacement for the 4 pin diode bridge, should fit in all boards with that pinout. something like this
  21. kevin gilmore

    goldenreference low voltage power supply

    coming soon, synchronous diode bridge using lt4320 and power fets lower dropout voltage, much less switching noise
  22. kevin gilmore

    some questions about electrostataic amp

    1) go and find complementary parts that work at 900v that are not obsolete 2) the load is more than you think. up to 20ma at 20khz 3) protect the diaphram 4) takes minutes to charge, quality of resistor is meaningless 5) 717 and 727 definitely have emitter follower output stages with current sinks.
  23. kevin gilmore

    Oscilloscope question...

    the cpu board has a known issue where the display goes blank. only the guy in Greece seems to know how to fix them. The one in the 2465a is different and does not seem to ever die.
  24. kevin gilmore

    Oscilloscope question...

    I have a 2465A which still works fine. I have a 2465B which I had to send the cpu board to Greece to get it fixed, it works fine. I also have a 2467B which had the same problem with the cpu board. All 3 still work fine. I did get a tek 1GHZ BW digital scope which I use a lot now, and a 300mhz rigol which is much more portable, and I use that a bit too. The next time the 2465's die, I will retire them.
  25. kevin gilmore

    stax t8000 clone (well sorta)

    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 the big thing lately, well might as well take the kgsshv-carbon design and replace the input fet with an input triode. bonus, no low voltage supplies. not a bonus, ksa1156 and ksc5026 run at close to 1 watt each. I should have a real t8000 end of june, but this should keep some of you busy. I expect joamat to have one built in less than 24 hours. no, no circuit board yet about 70 volts on the plate of the tube, same as t2. optical servo from kgsshv-carbon will work fine (but then you need the low voltage supplies) kgsshvcarbontubeinput.PDF