Hello,
In the schematic from TT Lummerland the power amp section is biased with two 560R resistor for a 12au7 Tube.
I Want to run the Lummerland with a ecc99, I have a Tube Town 30VA toroidal transformer and a TT 10watt ec99 output transformer (15k OT impedance).
In the other low TT plans, we can see that ecc99 is biased as follow  (with same +B voltage):

- Low Molly 270R+100uf cap
- Low Wild 13 330R+47uf cap
- Low Emma 2x560R resistors
- Low hot Lukas 330R+47uF

What config would I choose for better perfomance in my plan? Should I leave the same bias setting for ecc99 and 12au7 tubes?


Best Regards from Spain.


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The emma 2x560R non bypassed cathode bias resistors runs fine for a ecc99 TT Lummerland with the 10watts OT, it set the bias about at 88% dissipation, not so far from 100% recommended for cathode bias in pentodes.

Best Regards from Spain.