PY 81 as power rectifiers?

[Terry]

To avoid using a separate bias supply you could use cathode bias (potential divider)

Unfortunately, because of the common cathode, this would provide way too much bias to the triode section as well.

However, by connecting HT- to the point marked -3V (Bias) and connecting a 70Ω (or near miss) resistor across the 10µF capacitor would provide grid bias to the output pentode (only) as in the Grundig circuit.

Varying the value of this resistor will vary the bias, if required.