Let's say I have a fixed biased EL34 push pull output stage with 380V on the plates, and 250V on the screens. What is the procedure to find the optimal plate-to-plate load needed for the output transformer? When I run through what I think is the proper procedure I get significantly different results than supposedly what the data sheet says is optimal. So either the data sheet is wrong or I am calculating it wrong. So I thought I would pop this question up to the forum gurus for some help. Can someone walk me through this, with a bit more precision than just guessing or merely interpolating the various columns on the data sheet? Yeah, I think you can get pretty accurate results through interpolating the on the data sheet, but I would like to understand the "proper" way to do this if all you have is a characteristic curve plot at the given screen voltage you want. How does the procedure change if I have a cathode biased stage with some known resistor size in the cathode circuit? Thanks.