I am building a pure pentode class AB1 push-pull amplifier using 7591 tubes. I was planning to use following operating voltages found in the datasheet: plates 450V, screens 350V, grid -16.5V. However, I noticed that in the datasheet these values are listed for a 6.6K load resistance. My transformer primaries (not ultralinear) are 7.7K. Do I need to adjust the operating voltages? If so, how do I do this? I have been studying information about loadlines and from what I can tell, as long as I stay below the max plate dissipation, I think I'm safe to just stick with the numbers in the datasheet. I have a fixed bias similar to what's used in a ST-70, so I plan to adjust the cathode bias current to 25mA, which I think will be safe considering the max plate dissipation is 19W. Is this right? Thank you!