Well, it's an AC/DC circuit, and neither a capacitive heater divider, nor tapping off grid bias by a rectifying diode from the heater chain, are techniques available when you operate the thing from DC mains.
As the bias voltage is 32V, this would be a sizeable amount to lose from the HT supply if cathode bias is used. Power output would be compromised.
Earlier this year, 'Radiophile' magazine published a design someone put together for a radio using 12V as power supply (ie 12V HT). I can't be certain of the output valves - EF98's I think, in push-pull, but again, grid bias for these was produced by a self-rectifying oscillator circuit.
As the bias voltage is 32V, this would be a sizeable amount to lose from the HT supply if cathode bias is used. Power output would be compromised.
Earlier this year, 'Radiophile' magazine published a design someone put together for a radio using 12V as power supply (ie 12V HT). I can't be certain of the output valves - EF98's I think, in push-pull, but again, grid bias for these was produced by a self-rectifying oscillator circuit.
