Quiescent plate current is about 11mA per tube, plus few mA for screen. I used a standard loadline calc to determine the bias point of -10.5V for the grid (or +10.5V at the cathode). For more powerful amps that use higher bias voltage and draw more current this wouldn’t be practical, but here it was sufficient to use two arrays of few LEDs to get the desired cathode voltage and current handing. As long as the LEDs are lit, they provide a constant voltage at the cathode, so it should sound more like fixed bias, without the added complexity of the bias circuit. That allows some interesting solutions that may not cheap or practical for bigger amps but fit great here. The circuit is my own design built from scratch specifically for my needs instead of scaling down a big power amp.
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