I want to convert my 81 2204 to El34. Still has what is probably original 6550 GE tubes. I don't know what the correct resistor values to use. With the 6550 the plate voltage is 380- 395 (I forget!) Grid leaks will be NOS 220k Piher. But what Piher value do I need to use for the bias feed resistor and trim resistor? I cant find any board shots of European 2204s with el34s. I'm guessing 220k feed and a 56k or 47k trim. I'm pulling the board to do it proper and don't want to do it twice!