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kevin gilmore

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kevin gilmore last won the day on April 26 2017

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About kevin gilmore

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    Staximus Maximus, Stax Mafia's Chief Cook and Bottle Washer

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  1. kevin gilmore

    Technical Assistance/Advice Thread

    v- is actually -370v and vref3 is -350v take a closer look at the original schematic
  2. 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
  3. 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.
  4. kevin gilmore

    Raal Requisite SR1a

    uberamp2 in single ended form. then you don't need the resistor box.
  5. 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.
  6. 2 grhv, 2 grlv78xx,2 grlv79xx, 1 main board, 1 mini t2 please
  7. kevin gilmore

    goldenreference low voltage power supply

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

    goldenreference low voltage power supply

    coming soon, synchronous diode bridge using lt4320 and power fets lower dropout voltage, much less switching noise
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. 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.