You need to also include a 1K grid stopper for the 10M45S. And a 2K2 or thereabouts carbon comp on the grid of the EC86. A 47-100R carbon comp between the anode and the CCS can be used to hedge against Oscillation in the UHF region.
And sometimes it is required to RC filter de B+ supply to get the voltage above the CCS at about 300VDC. You then drop about 150V across the 10M45S. This R is about 100 Ohms per volt of drop. So say your coming down from 400 you need a 10K resistor for the RC filter section with a 3W wattage rating because the resistor sees about 1W of dissipation.
Current set resistor is 330R for about 10mA +-1mA you can also use a parallel combination of 680R and a 1K pot. This way nothing breaks if the pot goes open circuit for some reason.
At 150V and 10mA working point your looking at about -1.8V grid bias, measured with the MK1 eyeball. A run of the mill red LED will give you a drop of about 1.8V at that current.
I have used the IRF820 quite a bit in the past as a source follower after a 12AX7 to drive a typical Marshall/Fender tonestack. Does very well!
What do you think about using an IRF820 in the same fashion here? (after an EC86 150 plate volts run about 10ma with CCS)? I could run the IRF820 approx 10ma with a 15k resistor to ground.
And I think I will connect the KT88 UL, not triode.
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