With OP - Ua=440V, Ug2=320V, Ug1=-20V, you can expect more then 100mA Ia+g2 current through each EL34. Much more then Pa max for EL34. For "resonable" bias of about Ia~50mA (and Ig2~5mA) you should change the "bias voltage" Ug1 to about -26V. If you don`t have adjustable "bias" pot, you can change the values of voltage divider resistors in "bias" supply to "enlarge" Ug1.