@BHK what is the max heater current that the BHK Pre can supply? I have found a wonderful sounding pair of Russian 6n6p (6h6n) tubes that are essentially 12bh7’s,… plot wise they work as the bias point falls around -2v (@5ma),… Heater current is ~700ma (per tube) though,… pretty much double a 12au7,… I don’t want to over tax/stress the heater supply if it’s not up to it…
One other question,… when using a cc source/drain on a tube, doesn’t that flatten out the load line from an operation standpoint? realizing that the bias point will still be the same and you arrive at that point in the same way (Pr\V),… the slope flattens out some because of the constant current being delivered, correct?.. thus operating the tube in a more linear area between the grid lines?
Anywho,… if you confirm that the Pre heater supply is up to snuff for the higher ma draw, then I would highly recommend the 6n6p as a tube to try,… you can get a nice matched pair for ~$40 so not crazy expensive either. Please note that you do not want the 6n6p-I as it is for impulse use and not suitable,…
Best!