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kevin gilmore

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Everything posted by kevin gilmore

  1. 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
  2. 2 grhv, 2 grlv78xx,2 grlv79xx, 1 main board, 1 mini t2 please
  3. 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
  4. kevin gilmore

    goldenreference low voltage power supply

    it may have something to do with the minimum voltage. But I have not tested it.
  5. 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
  6. 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
  7. 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
  8. 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
  9. kevin gilmore

    goldenreference low voltage power supply

    coming soon, synchronous diode bridge using lt4320 and power fets lower dropout voltage, much less switching noise
  10. 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.
  11. 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.
  12. 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.
  13. 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
  14. kevin gilmore

    stax mafia circuit boards

    hopefully i cleaned this up and its the current versions of everything http://gilmore.chem.northwestern.edu/boards/
  15. kevin gilmore

    Technical Assistance/Advice Thread

    easiest to print out the file 1:1 from the gerbers. If your printer is exact, and virtually all laser printers are, this is the most accurate way. then center punch, drill, then tap.
  16. 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
  17. updated Megatron schematic. If you manage to figure out what the stax mafia is doing, please let us know. We are having a hard time keeping track of it all
  18. kevin gilmore

    Why no KG class AB ?

    long time ago there was a Yamaha integrated amp that had an A/AB switch. like about 1978. really nice thing, would make a perfect headphone amp if you can find one that still works. in fact the CFA amp is a A/B amp with the bias between 150 and 200ma. These days that kind of bias into just about any headphone results in pure class A operation. The uberamp2 is also a A/B amp with the bias between 2 and 3 amperes. about 100 watts into 8 ohms balanced.
  19. kevin gilmore

    grounded grid

    kgsshv-carbon with the sic-fets turned into 6ca7 was going to be next year
  20. kevin gilmore

    krell ksa5 klone

    Both Birgir and I have wanted one of these for quite a while, and they never seem to show up. So with a little help from one of the members here we were able to reverse engineer this one. http://gilmore.chem....rn.edu/ksa5.pdf http://gilmore.chem....rn.edu/ksa5.jpg still have work to do on the power supply. All the parts are still available, but identical and compatible parts also available. mpsw06 and mpsw56 and lsk389 I think this one is fairly cheap to do. And easy to assemble. Single channel is 10 x 3.65 inches. Single ended not really a HE6 killer, but balanced, a HE6 heavyweight for sure. If you replace the servo opamp with opa445, then you can go up to +/-35v rails. Then its definitely a HE6 killer single ended. picture of the original http://gilmore.chem....du/ksa5orig.jpg single ended with +/-21 power supplies, it does 10 vrms into 4 ohms or more. balanced 20 vrms into 8 ohms or more. single ended with +/-35 power supplies, it does 16 vrms into 4 ohms or more. balanced 32 vrms into 8 ohms or more.
  21. a number of lab power supplies have an adjustable current limit, so one of those set appropriately would be identical to the smps supply without the extra noise. but it would be easier and a bit cheaper to build a diy version with grlv and grhv supplies, a real transformer, in a standard heatsink chassis, with the outputs transistors on the heatsinks etc. then it would last more than 3 years. Those smps supplies when they get old, the main cap dries out, and usually bad things happen, especially to the output voltage.
  22. Unlikely to be a transient but only Alex knows at this point. Something with the clever way the filament and high voltage power supplies start up. You would think that rudimentary real world testing would have found this before a batch of them were made. then again on the liquid carbon version 1, using balanced and unbalanced headphones at the same time, and the amp blows up, something else that should have been caught before a large batch were made.
  23. so here is a reason not to buy the LP. if you turn off the switching power supply (or a power hit, or unplugging it) with the amplifier power switch on, a mosfet in the amplifier power supply fries. another of the many reasons why rail splitter power supplies are a bad idea.
  24. a number of people are complaining that there is no gain switch and the default gain is too high. kind of what you would expect from a current mirror feeding a tube. evidently its dc coupled but no pictures good enough to reverse engineer. If you go by the price of the cth x 2, this should be about $450 max.
  25. kevin gilmore

    New JDS Labs Atom Headphone Amp

    lets see jds atom $99 opamp and output buffer, lots of feedback, dual power supply, probably the lowest thd of the bunch. made in usa schiit magni3 $99 discrete current feedback amp, minimal feedback, dual power supply, probably the highest thd of the bunch. made in usa monoprice liquid spark $99.99 voltage feedback amp, fair bit of feedback, rail splitter power supply, in the middle for thd.made in china sounds like a big pile of same same