Looking to draw a loadline for 6EM7 section 2. Steve states that the load (Z)=(max V - quiescent V)/quescient I. I'm looking at Ic=50mA and Vq=210V. Is the load the primary impedance for the OPT? So if I'm using a 5K OPT the max V on the loadline at 0 plate current would be 460V. Then draw a line from the 460V,0mA point through the 210V,50mA point and figure all the other parameters from there?

I refuse to build anyhting till I can go through and explain/understand why everything is what it is.

Thanks

Hi, I`m back...
Load lines - simplified:

-the OP you chose (say, 200V/50mA/-30V - with respect to max Ia and Pa values) "determines" your "optimal" load (yes, this is your primary impedance - simplified). The AC current can "swing" from quiescent value (Iaq=50mA) to the double value, max. 100mA, and from "quiescent" Ug value (-30V from Ua/Ia/Ug diagram for 6EM7-2) to the Ug=0V, max. peak in class A1.

-draw the line through our "O" point (200V/50mA/-30V) and through another point, "A" (Ia=100mA, Ug=0V, and we read Ua=63V)

-point "B" can be another "extreme", (about 292V/16mA/-60V)

-our Ra, or primary load is (from Ohm`s Law) Ra=Ua/Ia, or "voltage swing" divided with "current swing", or:
Ra = (UaB - UaA) / (IaB - IaA) = (292-63)/(0,1-0,016) = 2,7 kOhms

-of course, you can just "extend" your line to the apsis and ordinate, to simplify Ra graphical finding, where Ia=0 and Ua=0, and you have
Ra = 335/0,125 = 2k7

-there`s a more, we want a symmetrical swing "around" your "O" point (min. distortion)...more horizontal LL is closer to this goal (increasing of the "minimal" Ra=2k7) on the less power "expense"

-for more, see this two messages:

http://audioroundtable.com/GroupBuild/messages/1111.html
http://audioroundtable.com/GroupBuild/messages/1113.html

At 210V/40mA 5K:8 ohm OPT

-34V bias voltage
Va= 50V
Vq= 210 V
Ve= 333V
Ia= 72mA
Ib= 54mA
Ic= 40mA
Id= 27mA
Ie= 15mA

Po= 2W
HD2%=6.25
HD3%=1.78
HD4%=0.89

At 210V/30mA 5K:8 ohm OPT

-37V bias
Va= 45V
Vq= 210V
Ve= 330V
Ia= 63mA
Ib= 45mA
Ic= 30mA
Id= 16mA
Ie= 6mA

Po=2W
HD2%= 7.84
HD3%= -0.58
HD4%= 1.45