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Anyone use SHUGUANG tubes?

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  • #121
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #122
      Originally posted by Chuck H View Post
      That's probably fine with the Shuguang tubes if you float the filaments 25 volts or more. I wouldn't use any Russian tubes for the CF and I wouldn't assume the Shuguangs for better than the typical 180V spec differential. Maybe they are.?. Why take the chance when it's easy to elevate the heaters.
      OK, I lied!!! The DC filament is from bridge rectifier from the 6.3V CT that power the heater of the EL34 and 12AT7 PI tube. I now float everything using the CT of the 6.3V winding to +60V. The rectified DC 6V have two 100ohm resistor one connected to the +ve and one to the -ve. The other ends of the 100 ohm resistors are tied together and AC grounded through a 63uF cap to ground. So the whole filament system is floating on +60V.

      I checked, Limiting value between filament to cathode of EL34 is 100V, 12AT7 is 90V and 12AX7 is 180V. I want to confirm I am good to go. I powered it up, everything seems fine.

      Thanks

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      • #123
        Never having built a DC filament supply I'm having trouble instantly visualizing your circuit, but it seems good. Keep in mind too that the CF failure may have been a fluke. Can't rule that out entirely. In case it wasn't though, you're at spec now for the 12ax7 circuits and that's better design practice.
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "If you're not interested in opinions and the experience of others, why even start a thread?
        You can't just expect consent." Helmholtz

        Comment

        • #124
          Originally posted by Chuck H View Post
          Never having built a DC filament supply I'm having trouble instantly visualizing your circuit, but it seems good. Keep in mind too that the CF failure may have been a fluke. Can't rule that out entirely. In case it wasn't though, you're at spec now for the 12ax7 circuits and that's better design practice.
          Like you said, better design for reliability. I didn't know better, but now I know.

          In my case, DC supply is nothing more than just run the 6.3VAC through the bridge rectifier to get about 6VDC. I just have two 100ohm resistors one on each side, then tie the other end of the two resistors together just like the typical old Fenders on the filament wires. But instead grounding the two resistors, I use a 63uF cap to give it AC ground as the filament is now at +60V.

          Thanks

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