Hi Atsunori,

Hi, quick questions.
o What is the topology of your output circuit,
single, push-pull, triode-connection or pentode-connection?
Its a push-pull amplifier

o What is the exact biasing method for the EL34?
o Is your cathode register very hot?

I was kinda confused for the cathode resistor voltage of 0.75-0.65[V].
If this is the actual bias voltage, it is too low for EL34 with plate
supply voltage of over 400[V]. So I assume that you are also applying
grid bias voltage somehow, but I don't know for sure.
Yes there's a grid bias (negative) voltage applied. The cathod resistor is
connected to ground and it was biased at 0.75V (to determine current through
the tube). Nope the resistor doesn't get hot at all.

Regards,
Mark