Yes the spice models for this operating range are not very enlightening. I used it in my example above primarily to draw the circuit. I did run some sims at higher voltages 25-50V just to get a ballpark idea on values but at 12V you are in test pilot mode.
That said the Low mu (around 6) and low rp (about 1K) are promising and the transfer characteristics hint that it ought to be more linear at low voltage than the 12AU7. Plate characteristics also hint that it should bias up with more headroom at the grid as well. The FB should help some with this as well.
FB might help the 12AU7 as well but it sure is tempting to try the 12B4.
That said the Low mu (around 6) and low rp (about 1K) are promising and the transfer characteristics hint that it ought to be more linear at low voltage than the 12AU7. Plate characteristics also hint that it should bias up with more headroom at the grid as well. The FB should help some with this as well.
FB might help the 12AU7 as well but it sure is tempting to try the 12B4.