I was thinking that a 6k6 will draw different current than an EL34 and that would change the voltages.

My amp with a Sylvania 5Y3 was right at 400v so I have added a 500 ohm resistor before the first filter cap and they are lower but still on the high side.

Also the ripple at the 40ufd cap is about 5v and causes hum if the negative feedback is used.