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In Reply to: RE: ultra-linear plate curves posted by thermionic addictions on March 18, 2015 at 13:58:55
You will some means of seeing what the plate response is with a varied g2 voltage. The curves with I_p at various g2 voltages( v_g1=0) are the only way to do this with the required accuracy. Triode curves will provide part of this, but only at V_g2=V_p
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
Hi Douglas
I did manage to find some triode curves for the 47 so I guess I'll
look over the info I have so far and go from there.
It might be easier to just buy a cheap U-L, OPT from Edcor and breadboard
it and see what it sounds like.
Cal
What is the UL tap % that you would like to use?
That depends on the tube characteristics. It is hard to generalize. For a low voltage 813, I think 20% is very good. The U-L curves depend on where you start; B+ that is. The 47 curves look like they'll like low percentage taps too.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Here is the UL characteristic with 20% tap, not sure it does much...
Hi Jazbo8
Thanks for the curves. But you are right they don't look that much
different than the pentode curves. I wonder how the traditional 43%
curves would look?
Cal
You are welcome, here is how it looks at 43%, a bit better...
Thanks again jazbo8.
That does look better. I think I will go with that since these are
easily obtainable "off the shelf" transformers.
By the way what curve tracer are you using for this it does a nice job.
Cal
You are welcome. The graph was not done with a curve tracer though, you can plot the UL characteristics with a simulation program if you have the SPICE model, which was what I did.
Interesting I might have to look into that.
Cal
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