A 6v6 has a plate dissipation of 12W
If you have the plate voltage and the current, you have the power dissipation :
P = U * I
So You must check the plate voltage, because 45mA at 300V or à 100V isn't not the same plate dissipation
![Wink ;-)](./images/smilies/icon_wink.gif)
Try to bias at 100% of your plate dissipation,a nd tell me how you feel the sound.