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About Laowei

  • Rank
    Limited Edition Bronze Participant
  • Birthday 06/07/1957

Profile Information

  • Gender
  • Location
    Vancouver, WA USA


  • Headphones
    Stax SR-009, SR-207, SR-003mk2
  • Headphone Amps
    KGHV-Grounded Grid
  • Sources
    Mac mini > Schiit Eitr > Schiit Yggdrasil
  • Other Audio Gear
    DIY PP 6V6 amplifier. ALTEC Model 19 speakers. ALTEC 809C Bolero speakers modified with vintage Great Heil AMT

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  1. grounded grid

    The graphic is from earlier in this thread where the PCB was first posted. It matches the traces on my PCB. Both appear similar and no printed Revision level is found. I bought my boards from another member, so probably the first. Kevin quickly drew up the GG (a tube version of the Carbon) to humor us vacuum tube Luddites. Your example looks like a later version. Basically the same, just tidied up a bit. The amazing thing is, even the quickie electrostatic amp designs that Kevin publishes, are simply incredible sounding. He is an irreplaceable source of inspiration for us DIYers.
  2. grounded grid

    Another couple of questions on grid connections in the output sections’ triode wired EL34s in the GG. 1) Per the GG PCB, and also the KGBH schematic, G3 (the suppressor grid) is tied directly to the cathode.This is the conventional connection for a grounded cathode circuit. In a grounded grid circuit where the cathode is driven, wouldn’t the added G3 parasitic load be harder/non-linear to drive? 2) In the DIY T2 and T8000 Sandwich PCBs, G3 is directly connected to the Plate. circuit. Is the suppressor function really needed in a grounded grid triode? Seems like driving the cathode only would be optimum in a grounded grid circuit. 3) Does the STAX T2, or DIY T2 have a history of being harder on the output EL34s’ G3, than a KGBH? I searched and could not find any mention of this. 4) Any advantage to cutting and modifying the traces on my GG PCB to try out the G3 to Plate connection? Thanks for any advise offered. T8000 Sandwich: GG:
  3. Schiit Yggdrasil

    Not in my experience. I hear a clear improvement between the Gen 5 and Gen 3 in my Yggy. Lots of others have reported the same.. The Eitr I first bought to try out crapped out on me, and I returned it. Their QC sucks. Have you contacted Schiit and complained? You may have gotten a sour unit too.
  4. Schiit Yggdrasil

    How does the Gen 5 compare to the previous USB input?
  5. Schiit Yggdrasil

    The Gen 5 USB does a lot better job than the stock Yggy Gen 3. For $100, I think you will be suprised and happy with the SQ after swapping them out. Do you have a lot of DSD content stored? Have you tried converting to hi-res PCM on the fly from your computer?
  6. Schiit Yggdrasil

    Much of a problem getting the LEDs on the main PCB lined up with the front holes on cover?
  7. grounded grid

    Thanks Kevin. Your generosity in taking the time to dissect and explain this is greatly appreciated.
  8. grounded grid

  9. grounded grid

    Not sure if that's true in a differential circuit. In other amps, I have increased the resistor and made the amp sound worse. Same current thru higher resistance equals larger voltage drop. Add AC and it would make things dynamically worse; higher voltage modulation on the screen.
  10. grounded grid

    I see the effective AC loop in the GG as this: ( Carbon shown) In a pentode, the screen grid electrostatic potential effects the electron flow to the plate. One can even use the screen to drive the plate if so inclined. Connecting G2 directly to the plate to simulate a triode, they would share the same potential, but G2 would fail due to excessive current draw. So to limit current, a resistor is usually added, which separates the screen from the plate potential depending on current across it. The higher the resistor value, the more difference. At DC, things look stable. Add in hundred of volts AC swing and the voltage across the resistor will modulate the screen potential. Adding the diode stops AC thru the screens (stabilizing the potential) and leaves it to pass only through the plates. I've found my GG to be able to play both a little louder and a little cleaner into my SR-009 after doing this addition.
  11. grounded grid

    With G2 connected to the plate with a resistor, as the screen passes current across the resistor, the screen will have a (slightly) different potential than the plate. With a CCS and DC, this relationship will be stable/constant. Varying AC load will vary the current across the resistor, and vary the screen potential relative to the plate..The varying potential on the screen can to an extent control current collection of the plate. Adding the diode, AC load is blocked from modulating the potential of the screen. The voltage drop across the diode is constant so should not be of consequence. Follow the AC loop in the differential circuit. 200Vrms (300Vpeak) voltage limit on TX2575. Two 100K wired in series in the GG.
  12. grounded grid

    A couple little things for now. Replaced the originally built Dale RN60 resistors in the global NFB circuit with ultra low noise and TCR TX2575 naked Z foil Vishay resistors (400VDC PS only). Also added a 1N4007 diode in series to the screen current limiting resistors that wire the pentode into triode operation. Similar as have done to my amps in the past. Will replace with Schottkys soon.
  13. grounded grid

    Just plugged in 2 matched pairs of used/tested above new, Valvo labeled Mullard xf3 tubes in my slightly modified GG. Now we're talking. That's how I remember real tube magic.... The only other tubes tried in this amp: 2000 vintage Svetlana Winged C EL34, NP JJ 6CA7, NP Gold Lion KT77. Not a drastic SQ difference with the OS Mullards, but the music simply flows with the xf3s, reproduced with a calm ease, clarity, presence and majesty absent in those other tubes. Everything sounds so balanced and right with these old guys.
  14. RIP some fuck or another

    RIP Cassini. Job well done.
  15. Happy Birthday johnwmclean

    Happy Birthday!