My Frankensteinian idea is to mate a Trainwreck Rocket preamp, PI and valve rectifier with a pair of KT66.
As I understand it, the 66s in a JTM45 are running at plate voltages IRO 450v, whereas the PT in a Rocket is putting out about 280v (over the 4 EL84s)
I don't know if I should:
1) spec the PT to give the 66s JTM voltages,
2) stick with the original PT and tweak resistor values to get to 450
3) stick with the original PT and either run at 280 or I'm able to double up on that with there ou being the two tubes and drop it back down to 450
4) ..no doubt there's a '4' ..there's always a '4'
I wonder if anyone can please set me straight?
Baz
The answer was never 42 - it's 1/137 (..ish)
Comments
If you want the full welly from the KT66s you will need to run them at 450V.
Yes, the preamp/PI supply should not exceed 300V but to get that from 450V is just Ohms law.
Each section of an ECC83 will draw about 1mA so add up all the sections and work out the value (and power rating!) of the dropper resistor needed. It is usual to have a dropper R for each section, each with a 10mfd 450V decoupling cap. This is a "cut and try" calculation. Do the best calculation you can with approximate currents, build it, then measure and adjust.
Dave.