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Thanks Romy.

Ok. I have installed a 30k resistor on the input and it reduced the drifting when the preamp is not connected. If my preamp is connected then I do not get any drifting at all and input voltage stays at 0v when I switch the amp off. No ticking when I plug/unplug the preamp. My gas tubes were drawing ~10.5mA so I reduced the R11 and R12 to 1.8R and now they draw 21mA. The gas tubes now regulate much better the voltage on both tubes got very close– 153V on positive and 152.8V on negative. Before the difference was around 1V. 

Should R13 & R14 be connected to ground?

I also checked the current draw for the first stage and I am getting around 13-14mA which seems a bit low if I need 25-35mA. Is this enough? My voltage on M is exactly 400v. Voltage on A is 193V. Bias -4.4v.

I can probably start putting everything into a case.

Regards

Gintaras

Rerurn to Romy the Cat's Site