B+ voltage load line question

[BobBeaston]

When a B+ voltage is measured and used to select components to bias your preamp is it with the tube connected or just an open power supply?

I have two B+ voltages derived from two rc filters fed by a bridge rectifier and a smoothing cap. All caps are 47uf. The two resistors are 5K. I used these voltages to design and then constructed my circuit. When I measure the B+ it is about 30 vdc lower. I never took into consideration the drop over the 5K resistor? Or is it just from loading the supply?

So which B+ voltage do I go with when constructing my load line... tubes connected or unloaded power supply?

Thanks

[SY]

Originally Posted by BobBeaston

So which B+ voltage do I go with when constructing my load line... tubes connected or unloaded power supply?

Thanks

Loaded (i.e., with tubes connected). Even though the loadline point is at zero current, the audio signals are much faster than the power supply cap charges and discharges, so the power supply voltage won't vary through the back-and-forth swing.

[DualTriode]

Hello,
Use real world B+. Plug it in measure the voltage across the tube, use that value. Draw the load line through the idle point.
DT
Just for fun!