[Phlogiston]

Russ

I never liked serialized filaments idea: for one, one tube dies and the rest extinguishes. And you have to figure which one.
Then in some places it can result in some bad scenarios. Like in Zenith portable radios.
I am fond of the idea using things as they are intended. Need a bias, use a resistor.
These off label usage is fine for cheap stuff where quality is traded off for space/cost.
Not in high end audio.

OH YES! I agree. Once anyone sees the meltdown caused by a open filament, they will too. I also wonder how these tubes run at 10V or less keep from going to sleep - seems like it would be hard on the cathode. The fisher I was referring to uses the 6BQ5 version that runs at 400V B+. Expensive and a quick failure with no bias.