Please critique my plans for a WE91 clone.

[sgerus]

I did some modifications to my White CF based on KevinR’s post and the tubecad article.

Now I have 330R on the upper plate, and 330R on the lower cathode.

I came up with 330R based on the 1/gm rule from the tubecad article.
So now I have:
373V @ plate (upper)
184V @ grid (upper)
188V @ cathode/grid
3.74V @ grid (lower)

This works out to 185V dropped across the upper valve, and 184V across the lower valve.

Is this normal? Should the upper valve drop more voltage than the lower valve?

 

[kevinkr]

I did some modifications to my White CF based on KevinR’s post and the tubecad article.

Now I have 330R on the upper plate, and 330R on the lower cathode.

I came up with 330R based on the 1/gm rule from the tubecad article.
So now I have:
373V @ plate (upper)
184V @ grid (upper)
188V @ cathode/grid
3.74V @ grid (lower)

This works out to 185V dropped across the upper valve, and 184V across the lower valve.

Is this normal? Should the upper valve drop more voltage than the lower valve?

This is excellent, about as close as you could reasonably be expected to get.. Your error is under 0.5%..

Well how does it sound?

Consider iterating that upper resistor a bit as the calculations get you close, but not always quite there. I found in my headphone amplifier that the value I calculated was off by about 50% or so. (I measured thd into the design load impedance to figure this out. Given the application and the high load current this might have been more critical with the headphone amplifier power stage than your driver.)