That Weber schematic is close to what I've been thinking about for my next project.
Compare the Weber (or Sunn) to an old Ampeg that used a 7199.
http://www.el34world.com/charts/Sche...Ampeg_B25B.pdf
The Ampeg uses a voltage divider on the screen and another voltage divider to set the operating point of the triode. I like that circuit because it would let me use a lower voltage rating on the screen cap. On my prototype, I used a 6AN8 with a .47@600V soldered right to the socket pins. I'll have to try smaller values as Alexander suggests.
I also had trouble setting the operating point of the pentode (using the Sunn circuit). Every NOS 6AN8 I tried gave a different plate voltage. I ended up just putting a trim pot in the cathode.
Have any of you guys had problems with getting a consistant pentode plate voltage between different tubes?
Compare the Weber (or Sunn) to an old Ampeg that used a 7199.
http://www.el34world.com/charts/Sche...Ampeg_B25B.pdf
The Ampeg uses a voltage divider on the screen and another voltage divider to set the operating point of the triode. I like that circuit because it would let me use a lower voltage rating on the screen cap. On my prototype, I used a 6AN8 with a .47@600V soldered right to the socket pins. I'll have to try smaller values as Alexander suggests.
I also had trouble setting the operating point of the pentode (using the Sunn circuit). Every NOS 6AN8 I tried gave a different plate voltage. I ended up just putting a trim pot in the cathode.
Have any of you guys had problems with getting a consistant pentode plate voltage between different tubes?
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