You could bias the junction point of the 2 heaters off B+, for noise control.
I don't understand this
Take the center connection of the two heaters, the two that you connected together and are not connected to the transformer, and place about 50V of bias using a resistor divider from B+. It's not a requirement, but can reduce hum.I don't understand this
What about connecting the center connection (center of two filaments) to ground ?
In addition to biasing that point off B+ with a resistive voltage divider, you ground that point via an electrolytic cap. of several μF. As the other posters stated, the network of 2 resistors and 1 cap. reduces vulnerability to hum and other noise.
+1 on the cap.... you ground that point via an electrolytic cap. of several μF. ...
If you want, you can calculate its value based on the resistance. But, I'd probably just make it 10uF and be done with it.
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