What do you think and are the values realistic?
I don't see any values mentioned. It's easy enough to calculate them from your pictures but why not simply mention them if you wish to get comments?
It's interesting that the Tungsol is not very linear at all yet it's one of my favourites. Maybe we should reverse our usual thinking!
What do you mean, I challenge you to find a tube with µ over 10 and better curves.
If you mean the load lines instead of the tube, then that's another thing. But then what would the make of the tube have to do with it. I don't see what you're talking about.
If anyone knows of any ultra linear power tubes to try for the high bias setting let me know.
Please don't use that phrase. Ultralinear is a thing, it's a topology invented to decrease distortion from pentode and beam tetrode output stages.
Once again, your output stage is a WCF, emphasis on the follower. It is not a gain stage.
Pentodes make good followers, very unlinear as gain stages.
FETs make supreme followers, very unlinear as gain stages.
Tungsol 6SL7 on left, GE 12/6SL7 on right. (GE is approximate due to going off scale at top).
I don't understand what's the point in presenting the same load lines on the same tube but two different manufacturers? If you don't like the graphics or the scale on one set of curves, simply use some other version of the curves. But why present more than one version of the same curves?
The new setting on the TS looks slightly more linear but neither operating point looks ideal.
Define ideal.
Once again you have to look at the situation, the circuit, as a whole.
1) You only need about +-10V swing on the anode, maybe +-30V max on huge transients. Consider that when looking at the load line.
2) You have gNFB; distortion is lowered via that. Balance is not corrected AT ALL via gNFB since the loops are within phases.
3) Because of point 2 even if you have a slightly worse load line you still come out ahead as a whole if you take care of the balance problem.