Howdy Folks,
Let me just share my test setup as that might be the best way to explain what I'm doing. I have a 6DJ8 with the halves paralleled in a grounded cathode config - trying to get a ton of gm for a phono project. I decided to go this route instead of using the more expensive 6C45pi tubes.
So I have it rigged up with:
- 110V B+,
- one of the IXYS CCS's set at 8.25mA (see Pete Millett's page)
- 200 ohm cathode resistor bypassed with a 470uF cap
I have a 100 ohm grid stopper (I still saw oscillations - need to make this MUCH bigger) with a 150K grid resistor. The output is a .22uF cap with another 150K resistor to ground.
How can I measure gm on this setup? The CCS makes this a little more difficult. I have both my audio analyzer and o'scope hooked up to it - certainly there's an easy method. Many thanks!
Shannon